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Vacuum DC breaker in DC motor armature circuit?

Vacuum DC breaker in DC motor armature circuit?

Vacuum DC breaker in DC motor armature circuit?

(OP)
I wonder if anyone has used vacuum breakers in DC motor applications.

Do we have the same concerns as in AC circuits? Inductance in a DC motor armature is usually a lot lower than in an AC motor. OTOH, the commutator bar breakdown voltage is a lot lower than what an AC motor can take.

I feel quite clueless here. Anyone?

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: Vacuum DC breaker in DC motor armature circuit?

Skogsgurra, I am not sure if vacuum breakers and contactors are rated for DC interrupting ability. If so, the rating should be listed on the nameplate.

One thing to keep in mind about interrupting DC current is that it is much harder than interrupting AC current since there is no zero crossing point. My understanding of interrupting current in an AC circuit using a breaker (air or vacuum) is that the interruption always happens at the zero crossing point.

Of course, for current limiting fuses this is not true. By definition, they just interrupt as fast as they can during the rise time of the fault current (during the first cycle).   

RE: Vacuum DC breaker in DC motor armature circuit?

Vacuum bottles are not rated for DC applications. Vacuum bottles have such a small gap that they can never break a DC current. They require the AC current zero to break the arc.
 

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