PR150 in DIN rail enclosure, front three-quarter view: terminal strip, three relays and three large capacitors

24 V DC emergency power changeover with alarm contact, 8 A

Article number PR150

The PR150 monitors the voltage of the main supply and quickly switches the output to the emergency supply as soon as that voltage drops, for example due to a short circuit or power failure. Large capacitors keep the voltage dip during changeover small, even at maximum load. A FET acting as an ideal diode prevents current from flowing back into a short circuit on the main supply and keeps heat dissipation so low that no heat sink is needed. Main and emergency supply are galvanically isolated from each other.

Supply main and emergency supply 24 V DC (±10 %)
Output 24 V DC to the load, 8 A continuous max.; reverse polarity protected
Isolation main and emergency supply galvanically isolated from each other

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Specifications

Specifications
Supply	Main and emergency supply 24 V DC (±10 %)
Output	24 V DC to the load, 8 A continuous max.; reverse polarity protected
Isolation	Main and emergency supply galvanically isolated from each other
Setup	"Power OK" threshold with two trimmers: main supply 18 to 22 V DC, emergency supply 15 to 30 V DC
Alarm contact	Changeover contact (COM, NC, NO); NO closed in normal operation. Switches 30 seconds after the main supply fails, or after about 35 seconds if the emergency supply fails while the main supply works
Indication	MAIN OK and EM OK LEDs, green in normal operation
Ambient temperature	0 to 55 °C
Dimensions	57 x 82 mm

Connections

Connections
Terminal	Function
Terminal 1	Alarm contact, common (COM)
Terminal 2	Alarm contact, normally closed (NC)
Terminal 3	Alarm contact, normally open (NO)
Terminal 4	Output minus, to the load
Terminal 5	Main supply minus
Terminal 6	Emergency supply minus
Terminal 7	Emergency supply plus
Terminal 8	Main supply plus
Terminal 9	Output plus, to the load

Datasheet (PDF)PDF, 144 kB

Setup

Connect the main supply to terminals 8 (plus) and 5 (minus), the emergency supply to terminals 7 (plus) and 6 (minus) and the load to terminals 9 (plus) and 4 (minus).
Connect the alarm signalling to terminal 1 (COM) and terminal 2 (NC) or terminal 3 (NO).
Switch on both supplies. In normal operation the MAIN OK and EM OK LEDs light green and the alarm contact NO is closed.
If required, set the main power OK threshold with the trimmer next to MAIN OK, between 18 and 22 V DC; turning clockwise raises the threshold.
If required, set the EM power OK threshold with the trimmer next to EM OK, between 15 and 30 V DC.

Application

Keeping 24 V DC equipment in buildings, installations and on board running when the main supply fails

Emergency power and emergency lighting

These modules switch automatically to an emergency supply or emergency circuit when the main supply fails. The PR149 and PR161 use relay logic at 230 V AC, without digital circuitry; for these two another operating voltage, such as 120 V AC or 24 V DC, is available on request. The PR150 switches over a 24 V DC supply, is fully analogue, without microcontroller or software, and has an alarm contact.

PR149: the emergency lighting switches on as soon as the 230 V AC mains fails; in normal operation the lighting is controlled with a wall switch. PR161: when the main circuit fails, the lighting is switched to the emergency circuit; the changeover can also be controlled externally. PR150: changeover from main to emergency supply at 24 V DC, up to 8 A, with alarm contact.

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