Posted 26 April 2005 - 08:54 AM
I have one question on Motor PF..
1)Is there motor pf can depend on the Type of connection of winding like star or Delta
2) At light load condition what will happend for the PF if i chnaged motor connection from star to delta or vice versa...
Posted 26 April 2005 - 09:20 AM
The displacement power factor of a motor is dependent on the magnetising current of the motor and the resistive loading of the motor.
If you take a given motor and change it from delta to star connection, the magnetising current will reduce to one third. If the resistive load compnent remains constant, then the power factor will improve.
In reality, the change from delta to star without changing the voltage, also reduces the power capacity of the motor and should not be done. This is not a means of improving the power factor of a motor unless the motor is operating at less than one third of it's rating.
Operation of a motor designed for delta connection on the "delta design" voltage at greater than one third load will cause an increased slip and excess power dissipation in the rotor. This could damage the motor.
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