Category: Studies-Load Flow-Impact Motor Starting

Question: How do I model a reduced voltage starter when performing an Impact Motor Starting study using the Load Flow?

Answer: Adjust the subtransient reactance (Xd”) to compensate for the reduced LRC of the reduced voltage starter. For example, if your LRC is limited to 4 x FLA, enter 0.25 as your Xd” (1/0.25 = 4)

Notes: To simplify things so you’re not always changing the Xd” depending on which state you want the motor in, clone it and have two motors at the same bus. One represents the starting condition and the other represents the running state. Toggle the appropriate motor In/Out of service depending on the study you’re running.