# Starting KVA Factor

I would to know what is the factor to be used for Variable speed drives for generator sizing for the starting KVA.?title=I would like to know what factor to be used for calculation of starting KVA using variable speed drive for pumping application to be used for Generator sizing. In some literatures, it states 1.2, others 1.5. what factor determines this value. Thanks

An example of generator sizing would be most welcome.

## 3 Answers

For inductive loads (electric motors) on a generator, it is common practice to use a factor of 3 to allow for start-up power surge. To minimize this load where several inductive appliances are driven by a single generator, the appliances should all be shut off before generator start-up and each one sequentially switched on at a minimum of 1 minute intervals. Generator shut-down can be done without reversing this procedure.

If you can provide an idea of what loads, what type of generator, what circuits are connected then the answer may be a bit more precise. But if your references are 1.2 and others 1.5 go with the larger number. The difference is not significant.

If the have any info from the specific VFD manufacturer, or can find it on the web, check their recommendations. Variable Frequency Drives can start motors with pretty low inrush current, so you may not need even 1.5X. But manufacture recommendations would be where I would start as there are several different drive designs.

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**Apr 30 '15**