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I can't find an explanation to determine, or the maths to calculate, the phase and line currents that a motor winding would expect to see during an attempted start if one supply phase is open circuit?
Would it be equivalent to Locked rotor current or less or more?
Can someone shed any light on this?
We're investigating the failure of a 75KW 415V 3ph 4 pole motor which has burnt out due to single phasing during a start attempt. the frame size is abnormally small for 75KW (250s/m) and as such the Locked rotor withstand time is only 18 seconds (cold).
Any opinions would be appreciated.
Kind regards,
kev
Would it be equivalent to Locked rotor current or less or more?
Can someone shed any light on this?
We're investigating the failure of a 75KW 415V 3ph 4 pole motor which has burnt out due to single phasing during a start attempt. the frame size is abnormally small for 75KW (250s/m) and as such the Locked rotor withstand time is only 18 seconds (cold).
Any opinions would be appreciated.
Kind regards,
kev