Soft-start, or not?

Motor starting equipment needed to prevent voltage problems

When a member’s project involves the installation of large new motors, Gary Allen, Northern Plains Electric’s Manager of Engineering, often gets questions on the cooperative’s motor starting equipment requirements. Allen is quick to point out the importance of understanding motor starting issues.

It’s been the cooperative’s experience, Allen explains, that the starting current required by single-phase motors over 10-horsepower, and on three-phase motors 25 horsepower and above, is often great enough to cause a noticeable and objectionable voltage dip for the customer who owns the equipment and for other customers connected to the same line. According to Allen, these larger motors, when installed without some type of reduced-voltage starter or soft-start capabilities, are a major cause of voltage issues on the system.

The fact that installations of large motors are increasing in number every year in Northern Plains Electric's service area, simply confirms that certain engineering standards must be established. Northern Plains Electric is in the process of implementing an engineering standard, which will limit the size of motors that can be installed on its system without some type of device to reduce, starting current. The engineering standard will address both single -phase and three-phase motors and will take into consideration the entire range of standard operating voltages available from the cooperative.

For more information on engineering standards for large motors, you may contact Northern Plains at (800) 882-2500.