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Motor Parameter/Soft Start

Motor Parameter/Soft Start

Motor Parameter/Soft Start

I inherited a motor model that was tested with and without soft start capabilities.

An input parameter requests a rated phase voltage, but they used the line voltage instead.

Could the soft start testing be an explanation for the use of Line Voltage?

I'm trying not to jump to the conclusion that the parameter was filled in wrong.(Additionally they reduced the starting current from 6pu to 2pu)

Any advice is appreciated.

RE: Motor Parameter/Soft Start

Check the machine connection: if it is delta, phase and line voltages are identical. As to why the current is limited to a much lower value: that’s what most “soft starts” really are - current limiters. The main reason for a soft start approach is to reduce the current draw during acceleration, and thus also reduce the observed voltage dip associated with the momentary overload (current) condition.

The starting current has to be low enough to minimize the voltage dip but high enough to allow acceleration of the load inertia in a reasonable time frame. Generally, a higher current occurs for higher inertia loads.

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