Is interrupting motor start current more challenging to a bkr ?
Is interrupting motor start current more challenging to a bkr ?
(OP)
I am interested to understand if the task of a breaker interrupting current is more challenging when interrupting locked rotor current (or close to locked rotor current during acceleration) as opposed to interrupting normal running current, no-load current, or fault current.
The scenario of interest is described thread238-286275: Switchgear fault after start of motor where the breaker opened after start when the machine was not quite up to speed yet.
The power system is 13.2kv resistance grounded thru a 20-ohm resistor
The breaker is GE Magne-blast
The motor is 7000 hp 13.2kv with 0.25 microfarad surge capacitors connected at its terminals
My first blunder into this question was thread thread237-286712: quiz: motor Vregen higher after interrupt from no-load or...? which looked at simple motor regenerated voltage ignoring capacitive effects. I think I probably missed the boat on that approach, because reading about breaker interruption terms like transient recovery votltage and it's rate of rise come up and capacitive effects seem important. Those terms (TRV, RRRV) are somewhat new to me, so I'm asking you guys for some thoughts on this question.
The scenario of interest is described thread238-286275: Switchgear fault after start of motor where the breaker opened after start when the machine was not quite up to speed yet.
The power system is 13.2kv resistance grounded thru a 20-ohm resistor
The breaker is GE Magne-blast
The motor is 7000 hp 13.2kv with 0.25 microfarad surge capacitors connected at its terminals
My first blunder into this question was thread thread237-286712: quiz: motor Vregen higher after interrupt from no-load or...? which looked at simple motor regenerated voltage ignoring capacitive effects. I think I probably missed the boat on that approach, because reading about breaker interruption terms like transient recovery votltage and it's rate of rise come up and capacitive effects seem important. Those terms (TRV, RRRV) are somewhat new to me, so I'm asking you guys for some thoughts on this question.
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(2B)+(2B)' ?





