Doubts about the use of star-delta start and soft start for motors
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I'm new to electrical appliances, and I have a question for you. Thank you in advance! ! ! 1. Regarding the starting method of the motor: The motor has direct start and reduced voltage start. Under what conditions and circumstances can it be started directly, under what conditions and circumstances is it necessary to start with reduced voltage, and what are the boundaries between the two methods (for example, whether the motor power can be started directly below a certain power, and if the motor power is above that, it needs to be started with reduced voltage) or what restrictions (such as the form of the transformer, the capacity of the transformer) 2. There are mainly star-delta and soft start methods for step-down starting. If there is no standard, then the choice of star-delta start and soft start is not subject to any conditions (such as transformer form, capacity) or something. If you don’t know the upper-end power supply (for example, you don’t know the transformer form, allocated capacity), etc., which method is more appropriate?
Since you can ask such a professional question, it means that you must have accumulated a certain amount of knowledge! There is no clear limit on how to choose. This mainly depends on experience and needs.
Our design is that below 30KW are all straight-up, and above are all soft-up!
1. Direct and soft start mainly depend on the size of the transformer. Both can be started directly on the premise that the startup process will not affect other loads under the transformer (for example, the bus voltage is not lower than 85% of the normal value). Generally, it does not exceed 30% of the transformer capacity and can be started directly. Of course, the premise is that the motor can withstand the impact torque of full voltage starting. 2. The capacity distinction is the same as above. Normal design uses soft start. Star-delta start has many disadvantages, such as secondary current impact and complicated wiring control.
Frequency converters are basically used for products above 22KW. Above 22KW, it depends on the control needs. Star-delta and soft start are rarely used.