Squirrel cage motor windings
Squirrel cage motor windings
(OP)
Hi, I heard once from a very clever electrician that the windings of a 3 phase induction motor can be wired up backwards and burn the motor out (i think slowly). What i mean by this is if you have 6 cores coming out of your motor all black, none labelled, then simply testing for each winding and taking one core from each for a star point and adding 3 phases to the other isn't good enough (assuming star connection is good enough). And that a further test has to be done to ensure the cores are correct, ie u1 v1 and w1 must be found. Has anyone else heard of this, because I always thought that as it was ac and the current was at 50hz, that the winding couldn't possibly be backwards.





RE: Squirrel cage motor windings
If you connect a 3 phase motor incorrectly there are 3 things that can happen (assuming IEC configurations for a dual voltage motor);
1) it runs fine, but in the wrong direction.
2) it doesn't run at all, i.e. no complete connections
3) it gets connected in star instead of delta or vice versa. In this case, if the motor were designed for star connection at your given voltage, and you connected it in delta, your applied voltage would be too high for that configuration and the motor would saturate, overheat and die eventually if left like that. If your motor were designed for delta connection at your given voltage, and you connected it in star, your voltage would be too low and the motor would stall from lack of torque, which may burn the motor out if left in that condition.
RE: Squirrel cage motor windings
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Squirrel cage motor windings
RE: Squirrel cage motor windings
RE: Squirrel cage motor windings
RE: Squirrel cage motor windings
RE: Squirrel cage motor windings
You will then get a three-phase sine voltage (a few volts or less) induced in the three windings. If all windings have the correct polarity, the voltage will be very low since three 120 degree voltages cancel. If you do not get almost zero volts, then change one winding and see if you get close to zero. If that winding didn't do it, then try next.
Depending of remanent flux in the rotor, you will get a higher or lower voltage. You may also get a non-zero voltage if the flux doesn't produce a perfect sine voltage in the windings. But you will always get the lowest voltage when the connection is correct.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Squirrel cage motor windings
For a standard 6 Lead Motors (Not for Dahlander or Part winding starting) the external connections could be Wye or Delta,6 Leads NEMA Motors are labelled with numbers from 1 to 6.The thread No. 237-153197 can help you with procedure to identify the leads, for low voltage squirrell cage motors. Normally For a wye connection we conect L1--1, L2--2 and L3-- 3 and Joint 4-5-6.I think when you are talking about "wired up backwards" you are refering to perform the Wye connection like L1--4,L2--5 and L3--6 and Joint 1-2-3.
Wondering, when you have 6 numbers missed leads you have to identify each one. When you have all numbers you can connect the motor in Wye or delta and energize with Voltage, but take account you are not shure if the new assigned numbers are the original lead labels,but the motor Runs,and the No load current can tell you if is working in the proper connection.
For Delta conection the thinks are not differents but you have two ways to perform Delta Connections the First is L1--1&6,L2--2&4,L3--3&5 Second: L1--1&5,L2--2-6 And L3--3&4.We have experienced two problems with air compressor motors when the starting method is star-delta, we noted the motor start proper in Wye but it trips the breakers when perform the change to Delta,to solve the problem we twisted the DELTA Connection (From fist to second or second to first), the problem dissapears.
Regards
Petronila
RE: Squirrel cage motor windings
Try each different connection - that is in Star connection - and apply power.
Label each lead with a,b,c a1,b1,c1.
connect start point, apply power to relevnt cable and listen to motor. If not good, interchange one of the phases. IE interchange a & a1.
apply power and try again.
If no good, cotinue interchangin process.
If power only applied for a short time, and motor has no load, you wont burn it out.