Primary injection of low voltage breakers without using aux power?

When primary injecting breakers I found that I need an aux power for a trip unit to turn on so that the LSI can be picked up. Otherwise, only the ground fault will alarm without any aux power connected. Is there a way to perform Pri inj without using aux power? I thought current would be enough to turn on any breaker. Any thoughts?

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The trip unit should come on once a few hundred amps of current are applied to the breaker but your test will be off because of that delayed response. If the ground fault alarm is picking up you might need to series two poles before it will work.

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It would also be helpful to tell us the Type of breaker and trip unit. Some manufacturer’s require 10% of all 3 phases or 30% of a single phase current to be pushed before the trip unit turns on. I’ve has a breaker trip on ground fault prior to meeting this requirement many times before.

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You would still need the auxiliary power on some Digitrips to adjust the LSIG setpoints in order to test the breaker. In some cases like Eaton they cost an arm and a leg for a power supply.

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Hey SecondGen I seen you had posted the 1150 and 520 trip unit curve excels for some reason when testguy added the new version it won’t allow me to download the excels, if by chance you still have them can you email them to me jesusdsantillan@yahoo.com. If you don’t that’s okay worth the try.

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Can you give a link where the original file was posted?

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This should be what you are looking for

Digitrip 520 Trip Curve Calculator.xls (39.5 KB)
Digitrip 1150 Trip Curve Calculator.xls (39 KB)
New Digitrip 1150 Trip Curve Calculator.xls (23.5 KB)

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Dope!! Thank you i appreciate you taking the time in doing this! definitely a time saver!

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I know I am a little late to reply but this may help another. I have come across this many times lately. I used to be able to push current to wake up the ETU. More times than not as of late, I am required to use AUX power to wake the unit up. I have even failed to wake the unit up using a secondary trip unit made by the manufacturer. Being in the field requires creativity when you don’t have the necessary equipment like an adjustable DC power supply unit that would match the breaker you are trying to test. However, in the gear you are testing there should be a “switching power supply” that feeds the breaker. They are small cube looking devices that are usually connected directly from the bus. They can have a supply voltage range that can vary, ie. 100-240 vAC. and the output will be what the breaker requires. I use a Milwaukee M18 inverter that supplies 120v with a suicide cord into the switching power supply. I have found this superior to a generator as it gives a UPS type power that a generator cannot. Hope this helps…

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With a lot of these newer breakers, you will have to series 2 phases to get proper pickups. We were instructed by Siemens to series 2 phases for the ETU850 trip units. This is becoming more and more common practice.

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