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Motor Starting Study

This isolated 60 Hz diesel generator power station at a new mine supplied two sizers fed from the mine’s crusher substation. The primary sizer was driven by a pair of 350kW motors and the secondary sizer by a pair of 250kW motors.

AEE was employed to study the performance of the power system when starting the sizers. Of primary importance was the maintenance of a voltage profile and system frequency consistent with stable operation of all power system components.

Dynamic models were constructed for:

  • The alternators,
  • The alternator governors and AVRs,
  • The sizer induction motors and
  • The sizer rolls which were coupled to the motors by fluid drives.

The studies simulated the motor starting performance with 3, 4 and 5 generators running in parallel. For each generation scenario, studies were conducted for both radial and parallel operation of the pair of 4.16/0.48 kV supply transformers at the crusher substation.

The studies yielded the following recommendations:

  • a minimum of four out of the five installed diesel generators should be running in parallel before attempting to start the sizers,
  • the time interval between starting the first motor and the second motor should be 800 ms for both sizers.[The time interval between starting the secondary sizer and starting the primary sizer was determined by others and was not within the scope of the electrical studies.]