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.]