Regarding the starting issues of low-voltage high-power motors
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The existing water pump is equipped with a 315kw motor and a 2000kvA transformer, with the load at 60%. The motor starts once a month. Can star-delta starting be used to ensure a smooth start without affecting other equipment? The design manual states that full-voltage starting is possible as long as the motor power does not exceed 30% of the capacity of the power supply transformer. So, can star-delta starting be used based on the current situation? Seeking advice
If it can start properly, then what are the concerns? In that case, use a star-delta starter; this power level should not be started directly, as it puts too much strain on both the transformer and the motor, and can lead to other problems.
My question is whether star-delta starting can indeed be used, and whether such starting will have an impact on other devices; after all, the transformer’s load was already at 60% even before this motor started operating.
It’s a very simple method: calculate the voltage drop at the motor terminals and on the busbars when starting the motor in star direct start or star-delta start mode. If the voltage on the busbars drops to 85% and other devices, especially frequency converters, are not affected, then star direct start or star-delta start can be used.
How is it calculated? Is it (load current + maximum starting current) * transformer short-circuit impedance?
The \"Manual for Industrial and Civil Power Distribution Design\" contains calculations of voltage drops under various starting conditions, which can be consulted