Recent content by gadha707

Phil: The OP confirmed it is a 3ph motor. Andy: What do you mean by the 50A breaker was too weak? Was it tripping during start up? If it was, the reason could either be a true motor overload condition or breaker with the wrong curve. I suspect it is the latter. What trip curve does your breaker...

A lot of good comments, but I think your questions are partially answered. So, let me try and fill the gaps in: All SF6 breakers have an internal safety mechanism which will lock-out a closed breaker in closed position, if the gas pressure becomes lower than a threshold value (set out by the...

We assumed it was a 3ph motor. Your calculation indicates it is a single phase motor. Can you confirm if it is a 3ph or 1ph motor? It appears that you shared the pump nameplate. Do you have the motor nameplate? The start up current is generally 6 times the full load current (Could be up to 12...

What's the motor FLA? Should come from the nameplate. My quick calc is saying it is circa 32A. Based on just that, a 40A MCB with D-curve should be sufficient, in my view.

Without a proper investigation, I would only be speculating: Questions: 1. Did the breaker fail during an operation or did it fail while in open or closed state? 2. At the time of the incident, did you have one or more unloaded transformers downstream (transformer energised but...

At 57Hz grid frequency, since the mechanical "power in" will remain the same (no further governor action as being at the end of the speed-droop curve already). While the grid frequency declined, the mechanical "torque in" will increase accordingly. This additional torque will accelerate the...

Check and compare the kVAR output of the machines, and you may find the source of amp discrepancy there. Ie, different reactive current due to different levels of excitation. If one of the AVRs is faulty or comes out of automatic voltage control mode to a constant field current mode for any...