Stored energy mechanism on Breakers - Easy Q for field guys

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angrymonkey

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I have a simple question about MV Breakers that I was hoping someone could help me with, time providing :D

I was reading over a specification which listed something similar to:

"The stored energy mechanism for the circuit breaker shall be charged by a universal electric motor."

Obviously, there is also a manual handle, but I am guessing only for emergencies in this case.


My issue is that I cannot picture what this "universal electric motor" looks like. All I can think of is the portable motor that can be used for racking the breaker.

Is this a motor internally mounted somewhere? Or is it some kind of portable device?


I realize this could be VERY simple, and thats my hope. But a picture or a link would be greatly appreciated :D I am guessing it is something I have seen plenty, just didn't realize what it was.

Thanks.
AM
 
A "universal motor" is a trade name for a motor like that on electric drills, mixers, etc, that has a wound rotor, brushes and commutator and can be used on AC or DC power.

For the MV breaker application, it makes sense to specify that kind of motor so that it can be used to recharge the mechanism using AC line power or as in substations, the 1225v DC battery control power.
 
Stored energy mechanism is a "techie" word used in effect to describe a spring.

To close contacts at a fast pace ( to avoid arcing) a spring is used which is wound up by the motor ( universal) or DC.

This motor is inside the Breaker housing. ( See attached image).

Cheers.
 
The circuit breakers that I'm familiar with use the motor to charge the closing spring . The tripping spring is compressed when the mechanism closes . This is for eqpt. 7.6 kv and above . Can't speak about lower voltage stuff .
 
angrymonkey said:
I have a simple question about MV Breakers that I was hoping someone could help me with, time providing :D

I was reading over a specification which listed something similar to:

"The stored energy mechanism for the circuit breaker shall be charged by a universal electric motor."

Obviously, there is also a manual handle, but I am guessing only for emergencies in this case.


My issue is that I cannot picture what this "universal electric motor" looks like. All I can think of is the portable motor that can be used for racking the breaker.

Is this a motor internally mounted somewhere? Or is it some kind of portable device?


I realize this could be VERY simple, and thats my hope. But a picture or a link would be greatly appreciated :D I am guessing it is something I have seen plenty, just didn't realize what it was.

Thanks.
AM
Click to expand...

The universal motor is basically a series wound DC motor designed to work on AC. I believe Hamilton Beach developed this motor in the nineteen twenties for use on electric mixers.

Since that time, it has been used in dozens of other applications such as portable electric tools, lawn trimmers, etc. They were often used with a rheostat in series for simple, cheap speed control.
 
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