Suggestions for device to test mccb

[oresakri]

Hello everybody,

i am interesting in buying a device to test MCCBs (Moulded Case Circuit Breakers), especially for Instantaneous overcurrent trip test. Any suggestions for devives? Is Sverger 780 suitable to do it?

 

[thermionic1]

We have a Sverker 780 (great value), but it can generate (105A). What frame size breakers (max) do you have to test? Good rule of thumb is 10x frame size for your current source. If you like Programma / Megger, I believe they have a unit called Ingvar that may be more suitable. If you get into really large breakers (2000-4000A), there are very large units made by Megger for this purpose.

 

[mc5w]

It might be cheaper to just buy another circuit breaker and stick that in. Conventional wisdom is that a molded case circuit breaker is considered to be fully depreciated when it has been in service for 15 years. If you are only interested in proving that the instantaneous trip works you could try using a bunch of 240/480 volt primary 24/48 volt secondary transformers to create a large amount of short circuit current in a 24-volt or 24Y41.5 volt electrical system. It will not verify the interrupting rating. That requires some expensive stuff.

What the fuse and circuit breaker manufacturers use for a 100,000-amp 480-volt short circuit test or smaller is a 2,000 horsepower or so synchronous which drives a flywheel and then in turn an 85 megawatt alternator. To run a 100,000-amp 750-volt test on a 690-volt nominal circuit breaker the manufacturer would need a 3,000 HP motor turning a flywheel and then a 135 MW alternator which was the size of the first 3 generating units at Cleveland Electric Illuminating Company's Eastlake generating plant before it was converted to a synchronous capacitor station. Such a test would be 542 amps at 138,000 volts and very obviously a power company would not allow that to be drawn through a transformer - the contract demand charge for a 138 KV service that big would be about 2 million US dollars per month comparable to the demand charges for a large steel mill. Using a motor flywheel generator set buffers the power flow to a level that is reasonable.

 

[oresakri]

Thank you all for the prompt response. I am interesting in inspections for several MCCBs on different costumes. What do you think should be the necessary Injection Current of the device? The main part of my costumes are industrial costumes.

 

[dpc]

oresakri,

"customers"

Surely there are specialized testing companies in your area that could be hired to do this? Commercially made test sets are available, but there will always be a maximum current level that they can produce that will limit the maximum breaker size. Primary current injection is the only reliable method of trip testing molded case breakers.

Cheers,

Dave

 

[emarch]

Have a look to our RAPTOR Primary Current test system. And contact us if you like what you see.

https://smcint.com/product/raptor-primary-system-electrical-testing-equipment/

Practically speaking, it will be able to deliver up to 10 KA in a 1000 A rated MCCB.

Regards