789819-01

NI PS-27 24 V, 20 A, 480 W, SINGLE PHASE INPUT ~~|~~ 

## NI PS-27 POWER SUPPLY 

- AC 100-240 V wide-range input 

- Width only 48 mm 

- Efficiency up to 95.6% 

- Excellent partial load efficiency 

- 20% Output power reserves (PowerBoost) 

- Easy fuse breaking—3 times nominal current for 12 ms 

- Safe Hiccup[PLUS ] overload mode 

- Active power factor correction (PFC) 

- Minimum inrush current surge 

- Full power between -25 °C and +60 °C 

- DC-OK relay contact 

- Current sharing feature for parallel use 

`•` 1 Year warranty 

## - PRODUCT DESCRIPTION SHORT FORM DATA ~~rs (ee~~ 

The NI PS-27 is a cost-optimized power supply without compromising quality, reliability, and performance. The most outstanding features of the NI PS-27 are the high efficiency, electronic inrush current limitation, active PFC, wide operational temperature range, and the extraordinarily small size. 

The NI PS-27 is equipped with quick-connect spring-clamp terminals preferred for applications that are exposed to mechanical vibration. 

The device also offers PowerBoost: power reserves of 20% that may be used continuously at temperatures up to +45 °C. 

High immunity to transients and power surges as well as low electromagnetic emission, a DC-OK relay contact, and a large international approval package for a variety of applications make this unit suitable for nearly every situation. 

|Output voltage|DC 24 V|Nominal|
|---|---|---|
|Adjustment range<br>Output current|24-28 Vdc<br>20-17.1 A<br>15-13 A|Factory setting 24.1 V<br>Up to +60 °C ambient<br>At +70 °C ambient|
||Derate linearly between +60 °C and +70 °C||
|PowerBoost|24 A<br>Up to +45 °C ambient<br>Linear decrease to nominal power between<br>+45 °C and +60 °C||
|Input voltage AC<br>Mains frequency<br>Input current AC|AC 100-240 V<br>50-60 Hz<br>4.26/2.23 A|±10%<br>±6%<br>At 120/230 Vac|
|Power factor<br>Input voltage DC<br>Input current DC|0.996/0.98<br>DC 110-150 V<br>4.64 A|At 120/230 Vac<br>±20%<br>At 110 Vdc|
|AC Inrush current|peak<br>10/4.5 A|At 120/230 Vac|
|Efficiency|94.2/95.6%|At 120/230 Vac|
|Power losses|29.6/22.1 W|At 120/230 Vac|
|Hold-up time|32/32 ms|At 120/230 Vac|
|Temperature range|-25 °C to +70 °C||
|Size (W x H x D)|48 x 124 x 127 mm|Without DIN rail|
|Weight|830 g||



## ORDER NUMBERS MAIN APPROVALS ~~rs (~~ 

Power supply NI PS-27 

For details and the complete approval list, see section 20. 

UL 61010-2-201 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

1/20 

NI PS-27 PHASE INPUTHASE INPUTINPUTNPUT ~~|~~ 

24 V, 20 A, 480 W, SINGLE PHASE INPUTHASE INPUTINPUTNPUT 

## TABLE OF CONTENTS ~~DO~~ 

|TABLE OF CONTENTS<br>~~DO~~|TABLE OF CONTENTSABLE OF CONTENTSCONTENTSONTENTS<br>~~DO~~|
|---|---|
|1.|Intended Use .............................................................. 2|
|2.|Installation Instructions .............................................. 2|
|3.|AC Input ...................................................................... 4|
|4.|DC Input ...................................................................... 5|
|5.|Input Inrush Current ................................................... 5|
|6.|Output ........................................................................ 5|
|7.|Hold-Up Time .............................................................. 7|
|8.|DC-OK Relay Contact .................................................. 7|
|9.|Efficiency and Power Losses ....................................... 8|
|10.|Lifetime Expectancy .................................................... 9|
|11.|MTBF .......................................................................... 9|
|12.|Functional Diagram ..................................................... 9|
|13.|Terminals and Wiring.................................................. 10|
|14.|Front Side and User Elements .................................... 10|
|15.|EMC ............................................................................ 11|
|16.|Environment ............................................................... 12|



|17. Protection Features .................................................... 12|
|---|
|18. Safety Features ........................................................... 13|
|19. Dielectric Strength ...................................................... 13|
|20. Approved, Fulfilled, or Tested Standards ................... 14|
|21. Regulatory Product Compliance ................................. 14|
|22. Physical Dimensions and Weight................................ 15|
|23. Application Notes ....................................................... 16|
|23.1.<br>Peak Current Capability ................................. 16|
|23.2.<br>Output Circuit Breakers ................................. 17|
|23.3.<br>Parallel Use to Increase Output Power .......... 17|
|23.4.<br>Parallel Use for Redundancy .......................... 18|
|23.5.<br>Series Operation ............................................ 18|
|23.6.<br>Charging of Batteries ..................................... 18|
|23.7.<br>Two Phase Operation ..................................... 19|
|23.8.<br>Use In a Tightly Sealed Enclosure ................... 19|
|23.9.<br>Mounting Orientations .................................. 19|



The information given in this document is correct to the best of our knowledge and experience at the time of publication. If not expressly agreed otherwise, this information does not represent a warranty in the legal sense of the word. As the state of our knowledge and experience is constantly changing, the information in this data sheet is subject to revision. 

No part of this document may be reproduced or utilized in any form without our prior permission in writing. 

Packaging and packaging aids can and should always be recycled. The product itself may not be disposed of as domestic refuse. 

## TERMINOLOGY AND ABBREVIATIONS ~~Ce~~ 

|**PE and**|**Symbol**|PE is the abbreviation for**P**rotective**E**arth and has the same meaning as the symbol|.|
|---|---|---|---|
|**Earth, Ground**||This document uses the term “earth” which is the same as the U.S. term “ground.”||
|**t.b.d.**||To be defined, value or description will follow later.||
|**AC 230 V**|**AC 230 V**|A figure displayed with the AC or DC before the value represents a nominal voltage with standard||
|||tolerances (usually ±15%) included.||
|||For example: DC 12 V describes a 12 V battery disregarding whether it is full (13.7 V) or flat (10 V).|For example: DC 12 V describes a 12 V battery disregarding whether it is full (13.7 V) or flat (10 V).|
|**230 Vac**||A figure with the unit (Vac) at the end is a momentary figure without any additional tolerances||
|||included.||
|**50 Hz vs. 60 Hz**|**50 Hz vs. 60 Hz**|As long as not otherwise stated, AC 230 V parameters are valid at 50 Hz mains frequency.||
|**may**||A key word indicating flexibility of choice with no implied preference.||
|**shall**||A key word indicating a mandatory requirement.||
|**should**||A key word indicating flexibility of choice with a strongly preferred implementation.||



## 1. INTENDED USE 

This device is designed for installation in an enclosure and is intended for commercial use, such as in industrial control, process control, monitoring, and measurement equipment or the like. 

Do not use this device in equipment where malfunctioning may cause severe personal injury or threaten human life. If this device is used in a manner outside of its specification, the protection provided by the device may be impaired. 

## 2. INSTALLATION INSTRUCTIONS 

## WARNING 

**Risk of electrical shock, fire, personal injury, or death.** 

- Turn power off before working on the device. Protect against inadvertent repowering. 

- Do not open, modify, or repair the device. 

- Use caution to prevent any foreign objects from entering the housing. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

2/20 

NI PS-27 PHASE INPUTHASE INPUTINPUTNPUT ~~)~~ 

24 V, 20 A, 480 W, SINGLE PHASE INPUTHASE INPUTINPUTNPUT 

- Do not use in wet locations or in areas where moisture or condensation can be expected. 

- Do not touch during power-on and immediately after power-off. Hot surfaces may cause burns. 

## NOTE 

## **Notes for use in hazardous location areas:** 

The device is suitable for use in Class I Division 2 Groups A, B, C, D T4 locations. 

## WARNING 

## **WARNING EXPLOSION HAZARDS!** 

- Do not use with DC input voltages. Do not use with AC input voltages below 90 Vac. 

- Use only in standard vertical mounting orientation with the input terminals on bottom of the unit. Substitution of components may 

- impair suitability for this environment. 

- Do not disconnect the device or operate the voltage adjustment unless power has been switched off or the area is known to be 

- non-hazardous. 

- A suitable enclosure must be provided for the end product. 

This device may only be installed and put into operation by qualified personnel. This device does not contain serviceable parts. The tripping of an internal fuse is caused by an internal defect. If damage or malfunction should occur during installation or operation, immediately turn power off and send the device to the factory for inspection. 

Install the device in an enclosure providing protection against electrical, mechanical, and fire hazards. Install the device onto a DIN rail according to EN 60715 with the input terminals on the bottom of the device. Other mounting orientations require a reduction in output current. 

Make sure that the wiring is correct by following all local and national codes. Use appropriate copper cables that are designed for a minimum operating temperature of 60 °C for ambient temperatures up to +45 °C, 75 °C for ambient temperatures up to +60 °C, and 90 °C for ambient temperatures up to +70 °C. Ensure that all strands of a stranded wire enter the terminal connection. Use ferrules for wires on the input terminals. Unused screw terminals should be securely tightened. 

The device is designed for use in pollution degree 2 areas in controlled environments. No condensation or frost is allowed. 

The enclosure of the device provides a degree of protection of IP20. The housing does not provide protection against spilled liquids. 

The isolation of the device is designed to withstand impulse voltages of overvoltage category III according to IEC 60664-1. 

The device is designed as “Class of Protection I” equipment according to IEC 61140. Do not use without a proper PE (Protective Earth) connection. 

The device is suitable to be supplied from TN, TT, or IT mains networks. The continuous voltage between the input terminals and the PE potential must not exceed 300 Vac. 

The input can also be powered from a battery or a similar DC source. The continuous voltage between the supply voltage and the PE/ground potential must not exceed 375 Vdc. 

A disconnecting means shall be provided for the input of the device. 

This device is designed for convection cooling and does not require an external fan. Do not obstruct airflow and do not cover ventilation grid! 

The device is designed for altitudes up to 5000 m. Above 2000 m, a reduction in output current and over voltage category is required. 

Keep the following installation clearances: 40 mm on top, 20 mm on the bottom, 5 mm on the left and right side. Increase the 5 mm to 15 mm in case the adjacent device is a heat source. When the device is permanently loaded with less than 50%, the 5 mm can be reduced to zero. 

The device is designed, tested, and approved for branch circuits up to 32 A (IEC) and 30 A (UL) without additional protection device. If an external fuse is utilized, do not use circuit breakers smaller than 10 A-, B-, or C-Characteristic to avoid a nuisance tripping of the circuit breaker. 

The maximum surrounding air temperature is +70 °C. The operational temperature is the same as the ambient or surrounding air temperature and is defined 2 cm below the device. 

The device is designed to operate in areas between 5% and 95% relative humidity. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

3/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

## 3. AC INPUT 

The device is suitable to be supplied from TN-, TT-, or IT-mains networks with AC voltage. For suitable DC supply voltages, see section 4. 

|AC input|nom.|AC 100-240 V||||
|---|---|---|---|---|---|
|AC input range||90-264 Vac||||
|||264-300 Vac|Occasionallyfor maximal 500 ms||for maximal 500 ms|
|Allowed voltage L or N to earth|max.|300 Vac|Continuous, according to IEC 60664-1|Continuous, according to IEC 60664-1||
|Input frequency|nom.|50-60 Hz|±6%|||
|Turn-on voltage|typ.|82 Vac|Steady-state value, see Fig. 3-1|||
|Shut-down voltage|typ.|72 Vac|Steady-state value, see Fig. 3-1|||
|External input protection|See recommendations in section 2.||See recommendations in section 2.|||
|||**AC 100 V**|**AC 120 V**|**AC 230 V**||
|Input current|typ.|5.15 A|4.26 A|2.23 A|At 24 V, 20 A, see Fig. 3-3|
|Power factor*)|typ.|0.996|0.996|0.98|At 24 V, 20 A, see Fig. 3-4|
|Crest factor**)|typ.|1.65|1.63|1.63|At 24 V, 20 A|
|Start-up delay|typ.|450 ms|450 ms|450 ms|See Fig. 3-2|
|Rise time|typ.|145 ms|145 ms|145 ms|At 24 V, 20 A const. current load, 0 mF|
||||||load capacitance, see Fig. 3-2|
||typ.|160 ms|160 ms|160 ms|At 24 V, 20 A const. current load, 20 mF|
||||||load capacitance, see Fig. 3-2|
|Turn-on overshoot|max.|200 mV|200 mV|200 mV|In single use mode, see Fig. 3-2|



> *) The power factor is the ratio of the true (or real) power to the apparent power in an AC circuit. 

> **) The crest factor is the mathematical ratio of the peak value to RMS value of the input current waveform. 

Fig. 3-1: Input voltage range 

Fig. 3-2: Turn-on behavior, definitions 

Fig. 3-3: Input current vs. output current at 24 V output voltage 

**==> picture [107 x 17] intentionally omitted <==**

**----- Start of picture text -----**<br>
Fig. 3-4: Power factor vs. output<br>current at 24 V output voltage<br>**----- End of picture text -----**<br>


October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

4/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

## 4. DC INPUT 

DC input nom. DC 110-150 V ±20% DC input range 88-180 Vdc DC input current typ. 4.64 A At 110 Vdc, 24 V, 20 A Allowed voltage (+) or (−) input max. 375 Vdc Continuous, according to IEC 60664-1 to earth Turn-on voltage typ. 80 Vdc Steady state value Shut-down voltage typ. 70 Vdc Steady state value **Instructions for DC use:** a) Use a battery or a similar DC source. WARNING ss © malfunction or damage the unit. BS/Ie b) Connect (+) pole to L and (–) pole to N. Fig. 4-1: Wiring for DC Input c) 

The device is suitable to be supplied from a DC input voltage. 

a) Use a battery or a similar DC source. WARNING A supply from the intermediate DC-bus of a frequency converter is not recommended and can cause a malfunction or damage the unit. b) Connect (+) pole to L and (–) pole to N. c) Connect the PE terminal to an earth wire or to the machine ground. 

## 5. INPUT INRUSH CURRENT 

An active inrush limitation circuit limits the input inrush current after turn-on of the input voltage. 

The charging current into EMI suppression capacitors is disregarded in the first microseconds after switch-on. 

**AC 100 V AC 120 V AC 230 V** Inrush current Ipeak max. 15 Apeak 12 Apeak 5.5 Apeak Temperature independent typ. 12 Apeak 10 Apeak 4.5 Apeak Temperature independent Inrush energy I[2] t max. 1 A[2] s 1 A[2] s 1 A[2] s Temperature independent 

Fig. 5-1: Typical turn-on behavior at nominal load and 25 °C ambient 

## 6. OUTPUT 

The output provides a SELV/PELV/EST1 rated voltage, which is galvanically isolated from the input voltage. 

The output is designed to supply any kind of loads, including capacitive and inductive loads. If extreme large capacitors, such as EDLCs (electric double layer capacitors or “UltraCaps”) with a capacitance >1 F are connected to the output, the unit might charge the capacitor in an intermittent mode. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

5/20 

NI PS-27 PHASE INPUTHASE INPUTINPUTNPUT ~~)~~ 

24 V, 20 A, 480 W, SINGLE PHASE INPUTHASE INPUTINPUTNPUT 

The output is electronically protected against overload, no-load, and short-circuits. In case of a protection event, audible noise may occur. 

|Output voltage|nom.|24 V||
|---|---|---|---|
|Adjustment range||24-28 V|Guaranteed value|
||max.|30 V|This is the maximum output voltage which can occur at the|
||||clockwise end position of the potentiometer due to|
||||tolerances. It is not a guaranteed value which can be achieved.|
|Factory settings|typ.|24.1 V|±0.2% in “single use” mode at full load, cold unit|
||typ.|24.1 V|±0.2% in “parallel use” mode at 20 A, cold unit (results to typ.|
||||23.9 V±0.2%at 24 A and typ. 25.1 V±0.2%at no load)|
|Line regulation|max.|10 mV|Between 90 and 300 Vac input voltage change|
|Load regulation|max.|100 mV|Between 0 and 24 A in “single use” mode, static value|
||typ.|1000 mV|Between 0 and 20 A in “parallel use” mode, static value; see Fig. 6-2|
|Ripple and noise voltage|max.|50 m Vpp|Bandwidth 20 Hz to 20 MHz, 50 Ohm|
|Output current|nom.|20 A|At 24 V and up to +60 °C ambient temperature; see Fig. 6-1|
||nom.|15 A|At 24 V and +70 °C ambient temperature; see Fig. 16-1|
||nom.|17.1 A|At 28 V and up to +60 °C ambient temperature; see Fig. 6-1|
||nom.|13 A|At 28 V and +70 °C ambient temperature; see Fig. 16-1|
||Derate linearly between +60 °C and +70 °C. See section 16.||Derate linearly between +60 °C and +70 °C. See section 16.|
|PowerBoost1)|nom.|24 A|At 24 V and up to +45 °C ambient temperature; see Fig. 16-1|
||nom.|20.6 A|At 28 V and up to +45 °C ambient temperature; see Fig. 16-1|
||PowerBoost decreases linearly to nominal power between +45 °C and +60 °C. See section 16.|||
|Fuse breaking current|typ.|60 A|Up to 12 ms once every five seconds; see Fig. 6-2. The fuse braking|
||||current is an enhanced transient current which helps to trip fuses on|
||||faulty output branches. The output voltage stays above 20 V.|
|Overload behavior|Continuous current|Continuous current|For output voltage above 13 Vdc; see Fig. 6-1|
||Intermittent current2)||For output voltage below 13 Vdc; see Fig. 6-1|
|Overload/|max.|29.8 A|Continuous current; see Fig. 6-1|
|short-circuit current|typ.|29 A|Intermitted current peak value for typ. 2 s|
||||Load impedance 10 mOhm; see Fig. 6-2|
||||Discharge current of output capacitors is not included. max.|
|||9.8 A|Intermitted current average value (R.M.S.)|
||||Load impedance 10 mOhm; see Fig. 6-2|
|Output capacitance|typ.|8500μF|Included inside the power supply|
|Back-feeding loads|max.|35 V|The unit is resistant and does not show malfunctioning when|
||||a load feeds back voltage to the power supply. It does not matter|
||||whether the power supply is on or off. The absorbing energy can be|
||||calculated according to the built-in large sized output capacitor.|



- 1) **PowerBoost** This power/current is continuously allowed up to an ambient temperature of +45 °C. Above +45 °C, do not use this power/current longer than a duty cycle of 10% and/or not longer than 1 minute every 10 minutes. 

- 2) At heavy overloads (when output voltage falls below 13 V), the power supply delivers continuous output current for 2 s. After this, the output is switched off for approximately 18 s before a new start attempt is automatically performed. This cycle is repeated as long as the overload exists. If the overload has been cleared, the device will operate normally. See Fig. 6-3. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

6/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

**==> picture [156 x 8] intentionally omitted <==**

**----- Start of picture text -----**<br>
Output Voltage (dynamic behavior, < 12ms) (V)<br>**----- End of picture text -----**<br>


Fig. 6-1: Output voltage vs. output current, typ. 

**==> picture [148 x 8] intentionally omitted <==**

**----- Start of picture text -----**<br>
Fig. 6-2: Dynamic overcurrent capability, typ.<br>**----- End of picture text -----**<br>


**==> picture [177 x 8] intentionally omitted <==**

**----- Start of picture text -----**<br>
Fig. 6-3: Short-circuit on output, Hiccup [PLUS ] mode, typ.<br>**----- End of picture text -----**<br>


**==> picture [169 x 8] intentionally omitted <==**

**----- Start of picture text -----**<br>
Fig. 6-4: Output voltage in “parallel use” mode, typ.<br>**----- End of picture text -----**<br>


## 7. HOLD-UP TIME 

The hold-up time is the time during which a power supply’s output voltage remains within specification following the loss of input power. The hold-up time is output load dependent. At no load, the hold-up time can be up to several seconds. The green DC-OK LED is also on during this time. 

|during this time.||||||
|---|---|---|---|---|---|
|||**AC 100 V**|**AC 120 V**|**AC 230 V**||
|Hold-up time|typ.|65 ms|65 ms|65 ms|At 24 V, 10 A; see Fig. 7-1|
||min.|54 ms|54 ms|54 ms|At 24 V, 10 A; see Fig. 7-1|
||typ.|32 ms|32 ms|32 ms|At 24 V, 20 A; see Fig. 7-1|
||min.|24 ms|24 ms|24 ms|At 24 V, 20 A; see Fig. 7-1|



**==> picture [376 x 8] intentionally omitted <==**

**----- Start of picture text -----**<br>
Fig. 7-1: Hold-up time vs. input voltage  Fig. 7-2: Shut-down behavior, definitions<br>**----- End of picture text -----**<br>


## 8. DC-OK RELAY CONTACT 

This feature monitors the output voltage on the output terminals of a running power supply. 

|Contact closes|As soon as the output voltage reaches typ. 90% of the adjusted output voltage level.|
|---|---|
|Contact opens|As soon as the output voltage dips more than 10% below the adjusted output voltage.|
||Short dips will be extended to a signal length of 100 ms. Dips shorter than 1 ms will be ignored.|



October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

7/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

Switching hysteresis typ. 1 V Contact ratings Maximal 60 Vdc 0.3 A, 30 Vdc 1 A, 30 Vac 0.5 A, resistive load Minimal permissible load: 1 mA at 5 Vdc Isolation voltage See dielectric strength table in section 19. 

Fig. 8-1: DC-ok relay contact behavior 

## 9. EFFICIENCY AND POWER LOSSES 

|||**AC 100 V**|**AC 120 V**|**AC 230 V**||
|---|---|---|---|---|---|
|Efficiency|typ.|93.6%|94.2%|95.6%|At 24 V, 20 A|
||typ.|93.5%|94.1%|95.5%|At 24 V, 24 A (PowerBoost)|
|Average efficiency*)|typ.|93.2%|93.8%|95%|25% at 5 A, 25% at 10 A,|
||||||25% at 15 A, 25% at 20 A|
|Power losses|typ.|2.5 W|2.2 W|2.2 W|At 24 V, 0 A|
||typ.|16 W|15 W|12.5 W|At 24 V, 10 A|
||typ.|32.8 W|29.6 W|22.1 W|At 24 V, 20 A|
||typ.|40 W|36.1 W|27.1 W|At 24 V,24 A(PowerBoost)|



> *) The average efficiency is an assumption for a typical application where the power supply is loaded with 25% of the nominal load for 25% of the time, 50% of the nominal load for another 25% of the time, 75% of the nominal load for another 25% of the time, and with 100% of the nominal load for the rest of the time. 

Fig. 9-1: Efficiency vs. output current at 24 V, typ. 

Fig. 9-2: Losses vs. output current at 24 V, typ. 

Fig. 9-3: Efficiency vs. input voltage at 24 V, 20 A, typ. 

Fig. 9-4: Losses vs. input voltage at 24 V, 20 A, typ. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

8/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

## 10. LIFETIME EXPECTANCY 

The lifetime expectancy shown in the table indicates the minimum operating hours (service life) and is determined by the lifetime expectancy of the built-in electrolytic capacitors. Lifetime expectancy is specified in operational hours and is calculated according to the capacitor’s manufacturer specification. The manufacturer of the electrolytic capacitors guarantees a maximum life of up to only 15 years (131,400 h). Any number exceeding this value is a calculated theoretical lifetime, which can be used to compare devices. 

||**AC 100 V**|**AC 120 V**|**AC 230 V**||
|---|---|---|---|---|
|Lifetime expectancy|123,000 h|149,000 h|173,000 h|At 24 V, 10 A and 40 °C|
||348,000 h|422,000 h|488,000 h|At 24 V, 10 A and 25 °C|
||48,000 h|60,000 h|94,000 h|At 24 V, 20 A and 40 °C|
||136,000 h|169,000 h|265,000 h|At 24 V, 20 A and 25 °C|
||23,000 h|31,000 h|54,000 h|At 24 V, 24 A and 40 °C|
||64,000 h|88,000 h|152,000 h|At 24 V, 24 A and 25 °C|



## 11. MTBF 

MTBF stands for **M** ean **T** ime **B** etween **F** ailure, which is calculated according to statistical device failures, and indicates reliability of a device. It is the statistical representation of the likelihood of a unit to fail and does not necessarily represent the life of a product. 

The MTBF figure is a statistical representation of the likelihood of a device to fail. A MTBF figure of, for example, 1,000,000 h means that statistically one unit will fail every 100 hours if 10,000 units are installed in the field. However, it cannot be determined if the failed unit has been running for 50,000 h or only for 100 h. 

For these types of units, the MTTF ( **M** ean **T** ime **T** o **F** ailure) value is the same value as the MTBF value. 

||**AC 100 V**|**AC 120 V**|**AC 230 V**||
|---|---|---|---|---|
|MTBF SN 29500, IEC 61709|422,000 h|445,000 h|590,000 h|At 24 V, 20 A, and 40 °C|
||790,000 h|832,000 h|1,060,000 h|At 24 V, 20 A, and 25 °C|
|MTBF MIL HDBK 217F|186,000 h|191,000 h|226,000 h|At 24 V, 20 A, and 40 °C;|
|||||Ground Benign GB40|
||256,000 h|263,000 h|313,000 h|At 24 V, 20 A, and 25 °C;|
|||||Ground Benign GB25|
||40,000 h|42,000 h|50,000 h|At 24 V, 20 A, and 40 °C;|
|||||Ground Fixed GF40|
||53,000 h|55,000 h|67,000 h|At 24 V, 20 A, and 25 °C;|
|||||Ground Fixed GF25|



## 12. FUNCTIONAL DIAGRAM 

Fig. 12-1: Functional diagram NI PS-27 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

9/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

## 13. TERMINALS AND WIRING 

The terminals are IP20 Finger safe constructed and suitable for field and factory wiring. 

|**NI PS-27**|**Input**|**Output**|**Signal Terminals**|
|---|---|---|---|
|**Type**|Quick-connect spring-|Quick-connect spring-|Push-in terminals|
||clamp terminals|clamp terminals||
|Solid wire|max. 6 mm2|max. 6 mm2|max. 1.5 mm2|
|Stranded wire|max. 4 mm2|max. 4 mm2|max. 1.5 mm2|
|American Wire Gauge|AWG 20-10|AWG 20-10|AWG 24-16|
|Max. wire diameter (including ferrules) 2.8 mm||2.8 mm|1.6 mm|
|Wire strippinglength|10 mm|10 mm|7 mm|
|Screwdriver|—|—|3 mm slotted to open the|
||||spring|



## **Daisy Chaining** 

Daisy chaining (jumping from one power supply output to the next) is not allowed. Use a separate distribution terminal block as shown in Fig. 13-1. 

Fig. 13-1: Using distribution terminals 

## 14. FRONT SIDE AND USER ELEMENTS 

## **A Output Terminals** 

Two identical (+) poles and three identical (−) poles 

- ( **+)** Positive output 

- **(−)** Negative output (return) 

## **B Output Voltage Potentiometer** 

Open the flap to adjust the output voltage. Factory setting: 24.1 V 

## **C DC OK LED** (green) 

On when the output voltage is >90% of the adjusted output voltage 

## **D Parallel Use Single Use Link** 

Link the two terminal poles when power supplies are connected in parallel. To achieve a sharing of the load current between the individual power supplies, the parallel use regulates the output voltage in such a manner that the voltage at no load is approximately 4% higher than at nominal load. See also section 23.3. 

## **E DC OK Relay Contact** push-in terminals 

The DC-OK relay contact is synchronized with the DC-OK LED. See section 8 for details. 

## **F Input Terminals** 

- **N, L** Line input 

PE (Protective Earth) input 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

10/20 

NI PS-27 PHASE INPUTHASE INPUTINPUTNPUT ~~)~~ 

24 V, 20 A, 480 W, SINGLE PHASE INPUTHASE INPUTINPUTNPUT 

## 15. EMC 

The EMC behavior of the device is designed for applications in industrial environments as well as in residential, commercial, and light industry environments. The output is allowed to be grounded or floating. 

Without additional measures to reduce the conducted emissions on the output (for example, by using a filter), the device is not suited to supply a local DC power network in residential, commercial, and light industrial environments. No restrictions apply for local DC power networks in industrial environments. 

|**EMC Immunity**|According to generic standards: EN 61000-6-1, EN 61000-6-2, EN 61000-6-3, and EN 61000-6-4|According to generic standards: EN 61000-6-1, EN 61000-6-2, EN 61000-6-3, and EN 61000-6-4|According to generic standards: EN 61000-6-1, EN 61000-6-2, EN 61000-6-3, and EN 61000-6-4|According to generic standards: EN 61000-6-1, EN 61000-6-2, EN 61000-6-3, and EN 61000-6-4|
|---|---|---|---|---|
|Electrostatic discharge|EN 61000-4-2|Contact discharge|8 kV|Criterion A|
|||Air discharge|15 kV|Criterion A|
|Electromagnetic RF field|EN 61000-4-3|80 MHz–2.7 GHz|20 V/m|Criterion A|
|Fast transients (Burst)|EN 61000-4-4|Input lines|4 kV|Criterion A|
|||Output lines|2 kV|Criterion A|
|||Signal lines (coupling clamp)|2 kV|Criterion A|
|Surge voltage on input|EN 61000-4-5|L→N|2 kV|Criterion A|
|||L→PE, N→PE|2 kV|Criterion A|
|Surge voltage on output|EN 61000-4-5|(+)→(−)|1 kV|Criterion A|
|||(+)/(−)→PE|2 kV|Criterion A|
|Surge voltage on DC-OK|EN 61000-4-5|DC-OK signal→PE|1 kV|Criterion A|
|Conducted disturbance|EN 61000-4-6|0.15 – 80 MHz|20 V|Criterion A|
|Mains voltage dips|EN 61000-4-11|0% of 100 Vac|0 Vac, 20 ms|Criterion A|
|||40% of 100 Vac|40 Vac, 200 ms|Criterion C|
|||70% of 100 Vac|70 Vac, 500 ms|Criterion A|
|||0% of 200 Vac|0 Vac, 20 ms|Criterion A|
|||40% of 200 Vac|80 Vac, 200 ms|Criterion A|
|||70% of 200 Vac|140 Vac,500 ms|Criterion A|
|Voltage interruptions|EN 61000-4-11|0% of 200 Vac (= 0 V)|5000 ms|Criterion C|
|Powerful transients|VDE 0160|Over entire load range|750 V, 0.3 ms|Criterion A|



**Performance criteria:** 

**A:** The device shows normal operation behavior within the defined limits. 

**C:** Temporary loss of function is possible. The device may shut-down and restart by itself. No damage or hazards to the device will occur. 

## **EMC Emission** 

|**EMC Emission**|||
|---|---|---|
|Conducted emission input lines|EN 55011, EN 55032, FCC Part 15,|Class B|
||CISPR 11, CISPR 32||
|Radiated emission|EN 55011, EN 55032|Class B|
|Harmonic input current (PFC)|EN 61000-3-2|Fulfilled for Class A equipment|
|||Fulfilled for Class C equipment in the load range from|
|||8 to 24 A|
|Voltage fluctuations, flicker|EN 61000-3-3|Fulfilled, tested with constant current loads, non|
|||pulsing|



This device complies with FCC Part 15 rules. 

Operation is subjected to following two conditions: This device may not cause harmful interference and this device must accept any interference received, including interference that may cause undesired operation. 

|**Switching Frequencies**|||
|---|---|---|
|PFC converter|100 kHz|Fixed frequency|
|Main converter|80 kHz to 140 kHz|Output load dependent|
|Auxiliary converter|60 kHz|Fixed frequency|



October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

11/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

## 16. ENVIRONMENT 

Operational temperature –25 °C to +70 °C 

The operational temperature is the same as the ambient or surrounding temperature. It is defined as the air temperature 2 cm below the device. 

Storage temperature -40 °C to +85 °C For storage and transportation Output derating 12 W/K Between +60 °C and +70 °C 1.33 A/1000 m or 5 K/1000 m For altitudes >2000 m, see Fig. 16-2 The derating is not hardware controlled. The user must take care to stay below the derated current limits to avoid overloading the unit. 

Humidity 5 to 95% r.h. According to IEC 60068-2-30 Atmospheric pressure 110–47 kPa See Fig. 16-2 for details Altitude Up to 5000 m See Fig. 16-2 for details Over-voltage category III According to IEC 60664-1 for altitudes <2000 m II According to IEC 60664-1 for altitudes >2000 m Degree of pollution 2 According to IEC 62477-1, not conductive Vibration sinusoidal 2-17.8 Hz: ±1.6 mm According to IEC 60068-2-6 17.8-500 Hz: 2 g 2 hours/axis Shock 30 g 6 ms, 20 g 11 ms According to IEC 60068-2-27 3 bumps/direction, 18 bumps in total 

Shock and vibration are tested in combination with DIN rails EN 60715 with a height of 15 mm and a thickness of 1.3 mm and standard orientation. 

Audible noise 

Some audible noise may be emitted from the power supply during no load, overload, or short circuit. 

Fig. 16-1: Output current vs. ambient temp. (Inom = 20 A; Iout with PowerBoost = 24 A) 

**==> picture [120 x 8] intentionally omitted <==**

**----- Start of picture text -----**<br>
Fig. 16-2: Output current vs. altitude<br>**----- End of picture text -----**<br>


## 17. PROTECTION FEATURES 

|Output over-voltage|typ. 30.5 Vdc|In case of an internal power supply defect, a redundant circuit limits|
|---|---|---|
|protection||the maximum output voltage. The output shuts down and|
||max. 32 Vdc|automatically attempts to restart.|
|Degree of protection|IP20|EN/IEC 60529|
|Penetration protection|>5 mm|For example, screws and small parts|



October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

12/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

Over-temperature Included protection 

Output shut down with automatic restart. Temperature sensors are installed on critical components inside the unit and turn off the unit in safety critical situations. These situations can happen, for example, when ambient temperature is too high, ventilation is obstructed, or the derating requirements are not followed. There is no correlation between the operating temperature and turn off temperature because this is dependent on input voltage, load, and installation methods. 

|||situations can happen, for example, when ambient temperature is<br>too high, ventilation is obstructed, or the derating requirements<br>are not followed. There is no correlation between the operating<br>temperature and turn off temperature because this is dependent<br>on input voltage, load, and installation methods.|
|---|---|---|
|Input transient protection|MOV (Metal Oxide|For protection values, see section 15.|
||Varistor)||
|Internal input fuse|Included|Non-user replaceable slow-blow high-braking capacity fuse|
|18. SAFETYFEATURES|||
|Class of protection|I|PE (Protective Earth) connection required according to|
|||IEC 61140|
|Isolation resistance|>500 MOhm|At delivered condition between input and output,|
|||measured with 500 Vdc|
||>500 MOhm|At delivered condition between input and PE, measured|
|||with 500 Vdc|
||>500 MOhm|At delivered condition between output and PE, measured|
|||with 500 Vdc|
||>500 MOhm|At delivered condition between output and DC-OK contacts,|
|||measured with 500 Vdc|
|PE resistance|<0.1 Ohm|Resistance between PE terminal and the housing in the area|
|||of the DIN rail mountingbracket|
|Touch current (leakage current)|typ. 0.12 mA/0.31 mA|At 100 Vac, 50 Hz, TN-, TT-mains/IT-mains|
||typ. 0.18 mA/0.45 mA|At 120 Vac, 60 Hz, TN-, TT-mains/IT-mains|
||typ. 0.3 mA/0.76 mA|At 230 Vac, 50 Hz, TN-, TT-mains/IT-mains|
||max. 0.16 mA/0.38 mA|At 110 Vac, 50 Hz, TN-, TT-mains/IT-mains|
||max. 0.23 mA/0.55 mA|At 132 Vac, 60 Hz, TN-, TT-mains/IT-mains|
||max. 0.39 mA/0.94 mA|At 264 Vac, 50 Hz, TN-, TT-mains/IT-mains|



## 18. SAFETY FEATURES 

## 19. DIELECTRIC STRENGTH 

The output voltage is floating and has no ohmic connection to the ground. The output is insulated to the input by a double or reinforced insulation. 

Type and routine tests are conducted by the manufacturer. Field tests may be conducted in the field using the appropriate test equipment that applies the voltage with a slow ramp (2 s up and 2 s down). Connect all input-terminals together as well as all output poles before conducting the test. When testing, set the cut-off current settings to the value in the table below. 

It is recommended that either the (+) pole or (–) pole shall be connected to the protective earth system. This helps to avoid situations in which a load starts unexpectedly or cannot be switched off when unnoticed earth faults occur. 

|||||A|B|C|D|
|---|---|---|---|---|---|---|---|
|Type test<br>Factorytest<br>Field test<br>Field test cut-off<br>Input<br>DC-ok<br>L>—<br>B”~~a~~e<br>~~AA~~<br>A<br>$ D|||60 s<br>5 s<br>5 s<br>Field test cut-off|2500 Vac<br>2500 Vac<br>2000 Vac<br>>10 mA|3000 Vac<br>2500 Vac<br>2000 Vac<br>>10 mA|1000 Vac<br>500 Vac<br>500 Vac<br>>20 mA|500 Vac<br>500 Vac<br>500 Vac<br>>1 mA|
|Y<br>Y||current settings||||||



Fig. 19-1: Dielectric strength 

- B[*) ] When testing input to DC-OK, ensure that the maximum voltage between DC-OK and the output does not exceed (column D). We recommend connecting DC-OK pins and the output pins together when performing the test. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

13/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

## 20. APPROVED, FULFILLED, OR TESTED STANDARDS 

|UL 61010|¢(U)usLISTED|UL Certificate<br>Listed equipment for category NMTR—UL 61010-2-201—Electrical equipment for<br>measurement, control, and laboratory use—Particular requirements for control|
|---|---|---|
|||equipment|
|||Applicable for US and Canada E-File:E330187|
|Class I Div 2|¢(U)usLISTED|UL Certificate<br>Listed equipment for category NRAD—Industrial control equipment for use in<br>hazardous locations|
|||Applicable for US and Canada E-File:E536050|
|||Temperature code: T4 Groups: A, B, C and D|
|IEC 61558-2-16|Safety Isolating|Test Certificate|
|(Annex BB)|Transformer|IEC 61558-2-16—Safety of transformers, reactors, power supply units, and similar|
|||products for supply voltages up to 1100 V|
|||Particular requirements and tests for switch mode power supply units and|
|||transformers for switch modepower supplyunits|
|Semi F47||Test Report|
||SEMI F47|Voltage Sag Immunity for Semiconductor Processing Equipment Tested for<br>AC 208 V L-L or L-N mains voltages, nominal output voltage, and nominal output|
|||load|
|IEC 60068-2-60||Manufacturer's Declaration (Online Document) Environmental|
||Corrosion|Tests, Flowing Mixed Gas Corrosion Test Test: Ke—Method 4<br>H2S: 10 ppb|
|||NO2: 200 ppb|
|||Cl2: 10 ppb|
|||SO2: 200 ppb|
|||Test Duration: 3 weeks, which simulates a service life of at least 10 years|
|ISA-71.04-1985|Cc<br>.<br>Gsisa-71.046W|Manufacturer's Declaration (Online Document)<br>Airborne Contaminants Corrosion Test|
|||Severity Level: G3 Harsh H2S: 100 ppb|
|||NOx: 1250 ppb|
|||Cl2: 20 ppb|
|||SO2: 300 ppb|
|||Test Duration: 3 weeks, which simulates a service life of at least 10 years|
|VDMA 24364|LABS|Paint Wetting Impairment Substances Test (or LABS-Test)<br>Tested for Zone 2 and Test Class C1 according to VDMA 24364-C1-L/W for|
||VDMA 24364-C1-L/W|solvents and water-based paints|



## 21. REGULATORY PRODUCT COMPLIANCE 

|EU Declaration of Conformity|The CE mark indicates conformance with the European|
|---|---|
||– EMC directive|
||– Low-voltage directive (LVD)|
||– RoHS directive|
|WEEE Regulation|Manufacturer's Declaration|
||EU Directive on Waste Electrical and Electronic Equipment Registered in|
||Germany as business to business (B2B) products|
||EU Directive 2012/19/EU WEEE-Reg.-Nr. DE 55837529|



October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

14/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

REACH Regulation Manufacturer's Declaration EU Regulation regarding the Registration, Evaluation, Authorization, and Restriction of Chemicals EU Regulation 1907/2006 RoHS-China Manufacturer's Statement Administrative Measures for the Restriction of the Use of Hazardous Substances in Electrical and Electronic Products 25 years 

## 22. PHYSICAL DIMENSIONS AND WEIGHT 

Width 48 mm Height 124 mm Depth 127 mm The DIN rail depth must be added to the unit depth to calculate the total required installation depth. Weight 830 g DIN rail Use 35 mm DIN rails according to EN 60715 or EN 50022 with a height of 7.5 or 15 mm. Housing material Body: Aluminum alloy Cover: Zinc-plated steel Installation clearances See section 2 Penetration protection Small parts such as screws, nuts, etc. with a diameter larger than 5 mm 

Fig. 22-1: Front view Fig. 22-2: Side view 

All dimensions in mm unless otherwise noted. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

15/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

## 23. APPLICATION NOTES 

## 23.1. PEAK CURRENT CAPABILITY 

The device can deliver peak currents (up to several milliseconds) which are higher than the specified short-term currents. 

This helps to start current demanding loads. Solenoids, contactors, and pneumatic modules often have a steady state coil and a pick-up coil. The inrush current demand of the pick-up coil is several times higher than the steady-state current and usually exceeds the nominal output current. The same situation applies when starting a capacitive load. 

The peak current capability also ensures the safe operation of subsequent circuit breakers of load circuits. The load branches are often individually protected with circuit breakers or fuses. In case of a short or an overload in one branch circuit, the fuse or circuit breaker needs a certain amount of over-current to open in a timely manner. This avoids voltage loss in adjacent circuits. 

The extra current (peak current) is supplied by the power converter and the built-in large sized output capacitors of the power supply. The capacitors get discharged during such an event, which causes a voltage dip on the output. The following examples show typical voltage dips for resistive loads: 

Fig. 23-1: 40 A peak current for 50 ms , typ. (2x the nominal current) 

Fig. 23-2: 100 A peak current for 5 ms , typ. (5x the nominal current) 

Fig. 23-3: 60 A peak current for 12 ms, typ. (3x the nominal current) 

Note: The DC-OK relay triggers when the voltage dips more than 10% for longer than 1 ms. 

Peak current voltage dips 

From 24 V to 16 V From 24 V to 21 V From 24 V to 17 V 

at 40 A for 50 ms, resistive load typ. at 100 A for 2 ms, resistive load typ. at 100 A for 5 ms, resistive load typ. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

16/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

## 23.2. OUTPUT CIRCUIT BREAKERS 

Standard miniature circuit breakers (MCBs or UL 1077 circuit breakers) are commonly used for AC-supply systems and may also be used on 24 V branches. 

MCBs are designed to protect wires and circuits. If the ampere value and the characteristics of the MCB are adapted to the wire size that is used, the wiring is considered as thermally safe regardless of whether the MCB opens or not. 

To avoid voltage dips and under-voltage situations in adjacent 24 V branches which are supplied by the same source, a fast (magnetic) tripping of the MCB is desired. A quick shutdown within 10 ms is necessary corresponding roughly to the ride-through time of PLCs. This requires power supplies with high current reserves and large output capacitors. Furthermore, the impedance of the faulty branch must be sufficiently small for the current to actually flow. The best current reserve in the power supply does not help if Ohms law does not permit current flow. The following table has typical test results showing which B- and C-Characteristic MCBs magnetically trip depending on the wire cross section and wire length. 

Maximum wire length[*) ] for a fast (magnetic) tripping: 

|~~a~~|**0.75 mm²**<br>~~a~~|**1.0 mm²**|**1.5 mm²**|**2.5 mm²**|
|---|---|---|---|---|
|**C-2 A**<br>~~:a~~|31 m<br>~~a~~|37 m|63 m|98 m|
|**C-3 A**<br>~~a~~<br>~~\~~|28 m<br>~~a~~<br>~~ee~~|34 m|51 m|78 m|
|**C-4 A**<br>~~\~~<br>~~ee~~|18 m<br>~~ee~~<br>~~ee~~|25 m<br>~~ee~~|38 m|58 m|
|**C-6 A**<br>~~ee~~<br>~~ee~~|9 m<br>~~ee~~<br>~~ee~~<br>~~ee~~|11 m<br>~~ee~~<br>~~ee~~|18 m<br>~~ee~~|26 m<br>~~ee~~|
|**C-8 A**<br>~~ee~~|6 m<br>~~ee~~|7 m<br>~~ee~~|1 m<br>~~ee~~|14 m<br>~~ee~~|
|**C-10 A**<br>~~ee~~|4 m<br>~~ee~~|6 m<br>~~ee~~|11 m<br>~~ee~~|13 m<br>~~ee~~|
|**C-13 A**|2 m|2 m|4 m|7 m|
|**B-6 A**|23 m|28 m|46 m|66 m|
|**B-10 A**|11 m|14 m|19 m|32 m|
|**B-13 A**|7 m|11 m|16 m|29 m|
|**B-16 A**|5 m|6 m|8 m|15 m|
|**B-20 A**|1 m|1 m|2 m|4 m|
|**B-25 A**|—|—|—|1 m|



*) Do not forget to consider twice the distance to the load (or cable length) when calculating the total wire length (+ and – wire). 

## 23.3. PARALLEL USE TO INCREASE OUTPUT POWER 

Power supplies can be paralleled to increase the output power. The output voltage of all devices shall be adjusted to the same value (±100 mV) in Single Use mode with the same load conditions on all units, or the units can be left with the factory settings. After the adjustments, set the unit to Parallel Use mode to achieve load sharing. The Parallel Use mode regulates the output voltage in such a manner that the voltage at no load is approximately 4% higher than at nominal load. See also section 6. 

The ambient temperature is not allowed to exceed +60 °C. 

If more than three units are connected in parallel, a fuse or circuit breaker with a rating of 30 A or 32 A is required on each output. Alternatively, a diode can also be utilized. 

Energize all units at the same time. It also might be necessary to cycle the input power (turnoff for at least five seconds) if the output was in overload or short circuits, and the required output current is higher than the current of one unit. 

Keep an installation clearance of 15 mm (left/right) between two devices and avoid installing devices on top of each other. Do not use devices in parallel in mounting orientations other than the standard mounting orientation or in any other condition where a reduction of the output current is required (for example, altitude). 

Pay attention that leakage current, EMI, and inrush current will increase when using multiple devices. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

17/20 

NI PS-27 24 V, 20 A, 480 W, SINGLE PHASE INPUT ~~|~~ 

## 23.4. PARALLEL USE FOR REDUNDANCY 

## **1+1 Redundancy:** 

Power supplies can be paralleled for redundancy to gain higher system availability. Redundant systems require a certain amount of extra power to support the load in case one device fails. The simplest way is to put two devices in parallel. This is called a 1+1 redundancy. In case one device fails, the other one is automatically able to support the load current without any interruption. It is possible that the defective unit will become a load of another power supply while configured in parallel usage. 

1+1 redundancy allows ambient temperatures up to +70 °C. 

Pay attention that leakage current, EMI, inrush current, and harmonics will increase when using multiple devices. 

## **Recommendations for building redundant power systems:** 

- Use separate input fuses for each device. 

- Use separate mains systems for each device whenever it is possible. 

- Monitor the individual devices. Therefore, use the DC-OK signal of the device. 

- Set the output voltages of all devices to the same value (± 100 mV) or leave it at the factory setting. 

- Set the devices to Parallel Use mode. 

## **N+1 Redundancy:** 

Redundant systems for a higher power demand are usually built in an N+1 method. For example, four devices, each rated for 20 A, are paralleled to build a 60 A redundant system. 

Pay attention that leakage current, EMI, inrush current, and harmonics will increase when using multiple devices. 

Keep an installation clearance of 15 mm (left/right) between two devices and avoid installing the devices on top of each other. 

Do not use devices in parallel in mounting orientations other than the standard mounting orientation or in any other condition where a reduction of the output current is required. 

For N+1 redundancy, the ambient temperature is not allowed to exceed +60 °C. 

## 23.5. SERIES OPERATION 

Power supplies of the same type can be connected in series for higher output voltages. It is possible to connect as many units in series as needed, providing the sum of the output 

voltage does not exceed 150 Vdc. Voltages with a potential above 60 Vdc must be installed with protection against touching. 

Avoid return voltage (for example, from a decelerating motor or battery) which is applied to the output terminals. 

Keep an installation clearance of 15 mm (left/right) between two power supplies and avoid installing the power supplies on top of each other. Do not use power supplies in series in mounting orientations other than the standard mounting orientation (terminals on the bottom of the unit). 

Pay attention that leakage current, EMI, inrush current, and harmonics will increase when using multiple power supplies. 

## 23.6. CHARGING OF BATTERIES 

The power supply can be used to charge lead-acid or maintenance free batteries. Two 12 V SLA or VRLA batteries are needed in series connection. 

## **Instructions for charging batteries:** 

- Use only matched batteries when putting 12 V types in series. 

- Ensure that the ambient temperature of the power supply stays below +40 °C. 

- Use a 32 A or 30 A circuit breaker (or blocking diode) between the power supply and the battery. 

- Ensure that the output current of the power supply is below the allowed charging current of the battery. 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

18/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

- The return current to the power supply (battery discharge current) is typ. 3.5 mA when the power supply is switched off (except when a blocking diode is utilized). 

- Set the device into Parallel Use mode and adjust the output voltage, measured at no load and at the battery end of the cable, very precisely to the end-of-charge voltage. 

|End-of-charge voltage|27.8 V|27.5 V|27.15 V|26.8 V|
|---|---|---|---|---|
|Batterytemperature|10 °C|20 °C|30 °C|40 °C|



## 23.7. TWO PHASE OPERATION 

The power supply can also be operated on two phases of a three-phase-system. Such a phase-to-phase connection is allowed as long as the supplying voltage is below 240 V[+10%] . 

Ensure that the wire, which is connected to the N-terminal, is appropriately fused. 

The maximum allowed voltage between a phase and the PE must be below 300 Vac. 

## 23.8. USE IN A TIGHTLY SEALED ENCLOSURE 

When the power supply is installed in a tightly sealed enclosure, the temperature inside the enclosure will be higher than outside. In such situations, the inside temperature defines the ambient temperature for the power supply. 

The following measurement results can be used as a reference to estimate the temperature rise inside the enclosure. For this measurement, the power supply is placed in the middle of the box; no other heat-producing items are inside the box. The temperature sensor inside the box is placed in the middle of the right side of the power supply with a distance of 1 cm to the power supply's side wall. 

||**Case A**|**Case B**|
|---|---|---|
|Enclosure size|**182**x 180 x 165 mm Rittal|**182**x 180 x 165 mm Rittal|
||Typ IP66 Box PK 9519 100|Typ IP66 Box PK 9519 100|
||plastic|plastic|
|Input voltage|230 Vac|230 Vac|
|Load|24 V, 16 A; (=**80**%)|24 V, 20 A; (=**100**%)|
|Temperature inside the box|52 °C|59 °C|
|Temperature outside the box|24 °C|24 °C|
|Temperature rise|28 K|35 K|



## 23.9. MOUNTING ORIENTATIONS 

Mounting orientations other than input terminals on the bottom and output on the top require a reduction in continuous output power or a limitation in the maximum allowed ambient temperature. 

The listed lifetime and MTBF values from this datasheet apply only for the standard mounting orientation. The following curves give an indication for allowed output currents for altitudes up to 2000 m. 

**==> picture [78 x 18] intentionally omitted <==**

**----- Start of picture text -----**<br>
A<br>Standard Orientation<br>**----- End of picture text -----**<br>


October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

19/20 

NI PS-27 

24 V, 20 A, 480 W, SINGLE PHASE INPUT 

## **B** 

Upside down 

## **C** 

Table-top mounting 

## **D** 

Horizontal cw 

## **E** 

Horizontal ccw 

October 2023/Rev. 2.2 NI PS-27    All parameters are typical values specified at 24 V, 20 A, 230 Vac, 25° C ambient and after a 5 minute run-in time unless otherwise noted. 

20/20