X-ray machines

[chevyx92]

I ran into a situation today where the xray machine wouldn't work, i found the breaker in the room was tripped and wouldn't reset. While troubleshooting I found there is a under voltage release accessory in the breaker. There was no under voltage condition but it wouldn't allow me to reset the breaker. This accessory operates at 480 volt. Once bypassed the breaker would reset. I determined the under voltage release to be bad. This is also tied into the emergency stop buttons in the rom . My question is, is this a common setup to have and under voltage release instead of a shunt trip?

 

[steve66]

I ran into a situation today where the xray machine wouldn't work, i found the breaker in the room was tripped and wouldn't reset. While troubleshooting I found there is a under voltage release accessory in the breaker. There was no under voltage condition but it wouldn't allow me to reset the breaker. This accessory operates at 480 volt. Once bypassed the breaker would reset. I determined the under voltage release to be bad. This is also tied into the emergency stop buttons in the rom . My question is, is this a common setup to have and under voltage release instead of a shunt trip?

Yes, its common. A undervoltage release is a more fail safe design than a shunt trip.

Picture the shunt trip. Voltage is provided by somewhere (maybe a low voltage power supply) and ran through normally open switches wired in parallel. If there is an open circuit in any of the wiring, or if the power supply is bad (maybe it has a blown fuse), nobody will ever know until they try to use the shunt trip and it doesn't work.

With the undervoltage relay, a power supply is wired through normally closed switches to the relay. If the power supply fails, or if there is an open circuit in any of the wires, the relay will operate and shut down the equipment. Then its obvious there is a problem with the emergency stop system.

In your particular case, it sounds like the power supply is just a straight 480V supply, but it probably has a fuse in series with it.

 

[chevyx92]

Yes, its common. A undervoltage release is a more fail safe design than a shunt trip.

Picture the shunt trip. Voltage is provided by somewhere (maybe a low voltage power supply) and ran through normally open switches wired in parallel. If there is an open circuit in any of the wiring, or if the power supply is bad (maybe it has a blown fuse), nobody will ever know until they try to use the shunt trip and it doesn't work.

With the undervoltage relay, a power supply is wired through normally closed switches to the relay. If the power supply fails, or if there is an open circuit in any of the wires, the relay will operate and shut down the equipment. Then its obvious there is a problem with the emergency stop system.

In your particular case, it sounds like the power supply is just a straight 480V supply, but it probably has a fuse in series with it.

480V to the LVR via a contactor, coil controlled by the emergency stops. That control circuit is 120 volt which comes from a step down XFMR. But I do see your POV on this, makes sense. Thanks.