Motor Rewinding

Catch the neck of who did rewinding and ask him to do it properly. That is the only solution without any cost.

That's fine. But what could be technical reasons for this?

First you need to check your electrical supply to the motor. There may be fault there that is causing the problem. Bad motor starter contacts could be dropping a load across them causing low voltage to the motor which would increase the current. Could also be the reason the motor went bad to begin with.

Also check the driven load maybe something there that is causing the motor to draw too much current. You don't say how much higher the current is then the name plate value. Is it just a little over the FLA or a lot.

Of the motor rebuild wrong size wire, wrong number of wraps, bad insulation on the wire causing a short, could be just something that they missed. They don't usually replace parts that appear to be good they are tested and meet the test they are reused. I would return it have them retested it again.

Probable cause is shorted turns. Try to check current in each phase. If there are shorted turns then current drawn would be different in different phases. If the current in all the phases is equal then another cause could be bent shaft that may be offering higher frictional load on the motor. you may like to check the run out of the shaft.

I am not an expert. Is it possible that one winding of the three is reverse connected?

If one winding of the 3 is reverse connected, you create a non symetrical magnetical field in the stator. In this case the motor will not turn at its nominal speed (minus 3 or 4 % lag) and the current in the 3 phases will differ very much from each other.

The topic opener only states that the current is to big, no big difference in each phase.

True, but it will turn and the RC will be higher than expected due to the increase in load

Another possibility is removing old windings by heating. Overheated iron can be damaged in magnetic qualities or (if an oxy torch is used) lamination corners can fuse together causing a shorted turn effect.

You don't say if you have a star or delta connection, lets assume its star connected internally.

could be that there are not enough windings per coil, but that reduces the HP of the motor and as you've put the motor back into its original duty driving a certain load at a certain current, then you are overloading the motor as the motor cannot produce the HP required.

could be that you have the correct windings but the rewinders did not phase the windings, that is, one winding is in reverse... does the motor make a loud hum or vibrate when running?

The only solution as all the other replies have stated.... take it back to the shop and get it rewound, AGAIN. There is NOTHING that can be done until its stripped down and examined

Two areas of concern in rewinding induction motors is the manner in which the original windings were removed. If by high heat via open flame, which is used to burn the varnish, it is highly possible that anealing has taking place in the silicon steal laminations of the stator pack. This in turn can effect the magnetic permeability of the material and reduce the efficiency of the motor performance. This can result in as much as a 5 % loss in efficiency which vary from instance to instance.

Another critical area is to ensure that there are no cracked rotor bars in the squirrel cage rotor, this test should always be undertaken when the motor is stripped. Some rewinders have a tendency to assume that the rotor is serviceable resulting in imbalances occurring.

A Professor told me that when you need to rewire a motor sometimes the rotor is damaged by copper from the windings. The copper burns in the rotor. The professor told us that often they turn off the copper form the rotor. So the diameter of the rotor becomes smaller and the air gap between rotor and stator becomes larger. Due to the larger air gap the losses are also larger. So when the losses become larger the current becomes higher for the same torque. So the nominal torque reduces. The professor told us this is a common problem. When the motor is rewinded and they put the motor back in the installation, the motor can't do his job anymore because of the reduce of the nominal torque.