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Thanks for the clear explanation. I was trying to find a quick way to determine the cross section area of an end ring without doing any thermal analysis or any detailed calculations. If there are 26 rotor bars with each bar of x cross section area carrying y current, I wasn't sure if I could...

Hi. For a caged induction motor, what is the current at one end of the short circuit end ring i.e. is it the summation of all of the rotor bar currents?

Thanks, electricpete. I have a scenario here. In the next 3 days or so, a 10kV 650kW 1450rpm motor will reach our repair shop for bearings replacement after more than 15 years of operation. The terminal markings, which are just some colored taped, have faded. I would assume that any residual...

Electricpete has attached a procedure on how to carry out the test with an oscilloscope. Can this test be done on a squirrel cage induction motor? Do I need to connect to an external source? How could there be residual of magnetism when there are no excitation source to the motor? I would...

What if you have just the stator only, but need to verify if the phase sequence is correct? What are the test equipment typically used to do such test, whether it is for small or large motors?

Typically, how much current is expected to be drawn to or flow from the motor?

I am more interest in an external fault.

What is the mechanism that would make it fail?

What are the things or calculation you would consider to determine if your motor could operate under fault conditions (e.g line-to-line or earth fault)? I am assuming that if a phase fault happen, you would get higher negative sequence current as a result of unbalance 3-phase motor. Therefore...

Many thanks all for giving your thoughts and comments.

I have read some online references on this topic and the method of calculating the torque and current under short circuit, reconnecting and starting consist of loads of calculus and numerical methods. Is there an easier way to do it so that I could use Excel to display the numbers and plots? I...

More current means more heat, but there would be a lag in temperature rise with the onset of higher current. My belief is that monitoring current is more effective than temperature. Also, if the pump is operating outside of this intended duty, it would also tell that it is not within its normal...

Thanks all for sharing your thoughts. Rhatcher, I thought of the same that bearings should have failed than impeller. I believe there was more political than technical outcome to this, but I was tasked to keep "within the scope" as described above, and determine adequate protection system for...

Hi. I am a new starter with a company which manufactures water-filled motors. There was an incident on a 6kV motor 400kW 2960rpm motor driving a centrifugal pump. It was summarised that the impeller damaged to the extent of fully worn out. As a result, the rotor shaft became unstable and caused...

Very often during testing while the rotor is locked, reduced voltage is applied to the motor, and current measured. 1. Do you normally use the straight line rule to extrapolate the current to the rated voltage? If it is a curve, what is the relationship, and how do you normally do the...

Since the rotating magnetic fields are sinusoidal in time, does it mean that at opposite polarity, the force produced by the magnetic field generated by the rotor current will push the stator coil away? Is that the reason coils vibrate? Does it mean that the rotor bars are now like a magnet...

jaraef, we do not have a TDR.

The suspected joint was being repaired, and the whole wire will be submerged in a bucket. But by doing so, the insulation test could not pinpoint the precise location should the wire fail the test or displayed low insulation reading.

Thanks for the response. I was wrong in my first post. It was actually a splice between 2 wires. The splice was hand-taped. So the damage is more like a crack. I was there when the Megger test was done to test the insulation resistance of the wire. It is more like rhatcher's Case 2, the probe...

Imagine you have a piece of long wire that consist of the copper conductor and insulation (EPR or XLP). There was a puncture on a small section of the wire. I have seen an engineer using a Meggar with one probe on the puncture area, and the other probe on the copper conductor to determine the...