rotor circuit single phasing question

M

Thread Starter

meonly

Can any one help me understand the phenomenon of rotor circuit single phasing and rotor ckt. earthed in slip ring induction motor. What will be effect on rotor and stator currents and voltages. Why motor run with heavy sound ?
 
Responding to Meonly's Thu, Jun 6, 4:35 pm query:

The rotor windings of a slip-ring (or wound-rotor) motor consist of three independent coils, usually connected in a 3-phase star (wye),
sometimes in delta (mesh)... as are the stator windings. Such motors are used in applictions requiring increased starting torque duty, limited
speed control capability, and load-sharing.

An opened-coil or shorted-coil in the rotor will produce an unbalanced electrical circuit causing an asymmetric interaction between the stator and rotor magnetic fields. The consequences are varied... no starting, excessive starting time or current, or poor running characteristics. As
for the noise, a growling sound will occur, caused by erratic vibration of both the stator and rotor magnetic structure.

I left the ground-fault for last. Its consequence will depend upon the generated voltage in the rotor windings. Remember, even an ungrounded
circuit is "grounded" via the conductor-to-ground capacitance. If the resultant capacitive-current flow is substantial, iron damage will occur in the rotor, and it will produce a buzzing sound.

Regards,
Phil Corso, PE
(Boca Raton, FL)
 
Further to my Thu, Jun 6, 5:57 response, a rather simple arcing-fault detector is available in the form of an AM radio receiver. It can even pickup very low-magnitude slip-ring arcing,

Regards,
Phil Corso, PE
(Boca Raton, FL)
 
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