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Old 08-27-2012, 07:47 AM   #1
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Default shunt trip breaker wiring

Hey I'm wiring a three phase 480v shunt trip breaker for an xray and I've never done one before. I know I need to have control power for the shunt coil in the breaker and I would imagine you'd want to power it off the feeder for the breaker. I was wondering if anyone had any input on a good way to establish a control circuit for this breaker?

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Old 08-27-2012, 07:49 AM   #2
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Quote:
Originally Posted by evan.lundberg4
Hey I'm wiring a three phase 480v shunt trip breaker for an xray and I've never done one before. I know I need to have control power for the shunt coil in the breaker and I would imagine you'd want to power it off the feeder for the breaker. I was wondering if anyone had any input on a good way to establish a control circuit for this breaker?
What's the coil voltage?

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Old 08-27-2012, 07:51 AM   #3
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Use a seperate 15 amp circuit breaker. From a reliable source, assuring the source and ST coil are the same voltage.
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Old 08-27-2012, 08:03 AM   #4
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I'm not sure what the coil voltage is because its not listed on the breaker I don't think....I'm double checking and having my boss look it up. Its a newer style square d breaker. Do you have to put a breaker lock on the control circuit so it doesn't get shut off?
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Old 08-27-2012, 08:04 AM   #5
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Check your x-ray schematics. The last time I did a x-ray machine the ST control came right from the machine. No need for the extra circuit.
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Old 08-27-2012, 08:05 AM   #6
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Originally Posted by evan.lundberg4 View Post
I'm not sure what the coil voltage is because its not listed on the breaker I don't think....I'm double checking and having my boss look it up. Its a newer style square d breaker. Do you have to put a breaker lock on the control circuit so it doesn't get shut off?

Not unless it is specified.
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Old 08-27-2012, 08:07 AM   #7
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Look on the side of the breaker. Usually there is a sticker for the added accessories. That sticker will tell you the voltage. If it is a field installed module you can open the breaker and get the voltage off the coil itself.
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Old 08-27-2012, 08:41 AM   #8
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If it is a shunt trip you apply power to trip the breaker.

Most X-ray manufacturers spec a control transformer fed off of the breaker you are controlling. That way your emergency shutoff will work without worry that the control circuit has been shutoff.

If it is a Ge X-ray room they provide a breaker with the control transformer included.
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Old 08-27-2012, 09:41 AM   #9
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A shunt trip is an accessory, not a type of breaker. It would be like saying "I have an air conditioned car"

So the breaker type won't tell you the coil voltage, it will be on a nameplate if it came from the factory with the shunt trip coil or if added aftermarket you may have to look on the coil itself.

Lots of ways to power it, capacitor trip can be a good solution. Post some more details and we will be able to help more.
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Old 08-27-2012, 09:43 AM   #10
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Cool thanks guys...I'm pretty sure its going to be a part of the xray machine now.
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Old 08-27-2012, 09:49 AM   #11
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I'm going to check the coil itself later this morning. Its a factory installed coil so I think I have to take the cover off the breaker to find the coil voltage. New xray machine isn't here yet so I don't have access to the machine specs. The old machine had an emergency trip wired internally and it was low voltage. Was hooked up to a pre made whip they dragged through pipe.
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Old 08-27-2012, 09:56 AM   #12
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Zog, I'm going to disagree ... but then, I expect it's more a matter of exactly what brand and model of breaker is being used.

The Square D "QO" panels use a breaker that occupies an extra space on the bussbars, and this provides the power to operate the breaker. All you need do is run a #12 wire from this 'extra pole' to your N.O. swirch, and land the return wire on the neutral buss. Obviously, this is a line-voltage arrangement.

By comparison, the Cutler-Hammer 'shoebox' sized breakers another customer has are ordinary breakers, to which you simply bolt on an accessory, as you describe. That accessory can be ordered for nearly any voltage.

I want the OP to do something even more daring than, say, hanging from a helicopter and touching an uninsulated 100KV line with his bare hand. I want him to read the directions for his breaker.
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Old 08-27-2012, 09:07 PM   #13
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This is all the info I have on the breaker as its an existing installation I'm just hooking up a new xray machine. Its a 100 amp three phase square d breaker disconnect being fed by 480v feeder. It has two black shunt trip wires coming out of it with a sticker that days shunt trip, 277v - 480v, 60hz, 8mA. Does this mean the coil is 277v and therefore one lead gets a neutral connection and the other gets powered when you hit the NO stop switch?
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Old 08-27-2012, 09:40 PM   #14
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Quote:
Originally Posted by evan.lundberg4 View Post
This is all the info I have on the breaker as its an existing installation I'm just hooking up a new xray machine. Its a 100 amp three phase square d breaker disconnect being fed by 480v feeder. It has two black shunt trip wires coming out of it with a sticker that days shunt trip, 277v - 480v, 60hz, 8mA. Does this mean the coil is 277v and therefore one lead gets a neutral connection and the other gets powered when you hit the NO stop switch?

Yes.
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Old 08-28-2012, 12:42 AM   #15
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I want him to read the directions for his breaker.
That's for sissies!!
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Old 08-28-2012, 04:09 PM   #16
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Thanks guys I appreciate the all the info!

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