Short Circuit Connection

Oh no. There is no chance of this 65kA flowing through the motor. This is the fault current which would occur if the system sees a 'bolted short-circuit' at the output of the transformer/s. This figure is required to select appropriate circuit breakers. Your motor will be protected adequately by a proper circuit breaker in the event of any short-circuit, and by a properly sized relay under overload conditions. There is no chance of any short-circuit downstream of the motor is there?

I suppose the circuit breaker will require some time to trip therefore is there a chance of 65KA flowing through the motor for few milliseconds.

No. You see, all electrical connections will come and TERMINATE at the motor terminals. Whatever the mode of starting of the motor, there is no electrical equipment DOWNSTREAM of a motor ... so there is no chance of any fault current flowing through the motor windings.(.. unless there is a short-circuit in the motor windings themselves .. in which case, no point in protecting it )

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Maintenance Circle Team(R)

The motor design/selection does not depend much, if at all, on the available short circuit currrent. This number is used instead for selecting fuses and/or circuit breakers that are capable of interrupting such current. (Some typical interrupting ratings are 10kA, 22kA, 100kA, 200kA, and others; which must be selected to equal or exceed the available short circuit current through the device.)

Because of the impedance of conductors from a breaker to a motor, the available short circuit current at the motor will be less than that at the breaker, but still it must be protected against.

Normally, the starting current of a motor is the maximum it will receive (around 6x full load current, depending on specifics). The 65kA (or 137kA) would not typically go to the motor, but rather to a shorted bus bar or cable "upstream" of the motor.

I am grateful to you all for illustrative explanations and prompt help.

Please also explain what is the difference between 65KA (steady state) and 137 KA (instantaneous). Are there any standard duration for both?

Depending on the point of the voltage wave at which short-circuit occurs, there will be a DC component which makes the current wave offset ... something like this one...a detailed explanation you can get from

http://www.energy.siemens.com/us/pool/us/services/power-transmission-distribution/medium-voltage-product-services/tech-topics-application-notes/techtopics44rev1.pdf

As per IEC, the circuit breaker with a 65kA capacity must clear a fault with a peak of 143kA.