Solving Power Quality Issues from Large Motor Starts using Fast-Acting Capacitor Bank Assistance

Starting a large motor, even with modern soft-start equipment is frequently problematic. With ever increasing focus on power quality, an Electric Cooperative can experience voltage sag problems when an industrial customer installs a large motor (400 – 2500 HP). Other customers can be adversely affected as well as the company with the motor(s). Of course, the coop is generally blamed by both.

Solving these problems is not trivial. Capacitor assistance can be a viable and relatively inexpensive solution but it must be done correctly. This paper will discuss the benefits (both for customers and for the utility), techniques, problems, relative costs and savings, alternatives, and analysis of capacitor assisted motor starting. Examples of actual installations and case studies will be shown.


  • Toby Lande, P.E. – VP of Engineering & Lead Design Engineer – Valquest Systems, Inc.