Breaker auto reset feature

[Williamexum]

Safety concern:
A modification that drives a tripped circuit breaker back to the closed position when valid 220 VAC power returns seems unsafe. Our 4 meter satellite tracking dish is being modified to prevent system shutdowns due to short-term power failures. The breaker is presently configured to be manually reset after an anlysis of an input power failure. The breaker is rated at 80 amps and sits just behind, (source side) a 400 VAC step-down transformer. On the load side, there are three breakers ahead of it that will not trip automatically. These breakers support servo motors, two 3-ton air-conditioning units and the hydraulic system that is used for raising and lowering a 500 lb tilt axis. The plan is to install multiple load contactors in front of the breaker that will magnetically close it. My concern is that repeated power outages or brown-outs where the power goes down and comes back up multiple times shortens the life of the antenna's systems. Under the present manual reset configuration, I can turn the other breakers off before reseting the 80 amp breaker. Please advise.

Bill in Germany

 

[barclayd]

To automatically reset a tripped breaker without investigating the cause is a dangerous situation.
What causes the breaker to trip in the first place?
IF your tracking dish is a critical operation, and IF your power is unreliable, you need UPS backup and possibly a generator.
I'm not sure what you mean about the 'contactor' that drives the breaker closed. There are factory-built motor operators that can open and close breakers, but you really don't want to do that.
db

 

[dbuckley]

If I read it right, the input breaker drops out when there is a power failure, and is currently manually reset, and the proposal is to automatically reset it.

As there was no fault that caused the breaker to open, merely loss of power, then there are no specific arguments against reclosing, other than the obvious (and in the industrial world, fairly common) mechanical safety concerns of stuff starting unexpectedly.

The second thing is you like to sequence the power to the downstream devices. If you can afford all this kit then you can afford a power sequencer to simulate your manual sequencing actions.

 

[nakulak]

what code is the local ahj enforcing ? (just curious)

 

[jim dungar]

Safety concern:
A modification that drives a tripped circuit breaker back to the closed position when valid 220 VAC power returns seems unsafe. Our 4 meter satellite tracking dish is being modified to prevent system shutdowns due to short-term power failures. The breaker is presently configured to be manually reset after an anlysis of an input power failure. The breaker is rated at 80 amps and sits just behind, (source side) a 400 VAC step-down transformer. On the load side, there are three breakers ahead of it that will not trip automatically. These breakers support servo motors, two 3-ton air-conditioning units and the hydraulic system that is used for raising and lowering a 500 lb tilt axis. The plan is to install multiple load contactors in front of the breaker that will magnetically close it. My concern is that repeated power outages or brown-outs where the power goes down and comes back up multiple times shortens the life of the antenna's systems. Under the present manual reset configuration, I can turn the other breakers off before reseting the 80 amp breaker. Please advise.

Bill in Germany

Breakers are often used in "automatic through over" applications. Most smaller frame (<100A) breakers are rated for hundreds of mechanical operations. Breaking the steady state load would be well within operating limit of the breaker and should not cause a significant reduction in life. It is likely that your transformer inrush is also within the design parameters (usually 10x for several seconds) of the breaker so that this will also not be a significant problem. My concern would be the life of the "motor operator" on the breaker.

Just add some timing logic to prevent the breaker from re-closing until the utility power has had a chance to stabilize. This is similar to the timing of automatic transfer switches which also do not want to short cycle the load. With a smart relay or PLC, you can even add a counter function to keep track of the number of operations of the breaker.

If you are are expecting many frequent operations then add a motor starter between the breaker and the transformer and have it perform drop out and turn on operation. A mechanically held device and a capacitor trip module would also mean that the starter coils would not need to be energized all of the time.

 

[Lxnxjxhx]

Isn't this called a recloser?

 

[jim dungar]

Isn't this called a recloser?

No.

A reclosure is a special device, without overload protection, that opens and closes automatically during fault conditions usually for a limited number of times before locking open. Operationally a reclosure is much more like a contactor than it is a circuit breaker.