Systematic approach, long-term solution for VFD-driven motors

Virtually all VFD-driven motors are vulnerable to bearing damage. To make the savings generated by VFDs sustainable, an effective long-term method of shaft grounding is essential. Although a grounding ring safely bleeds damaging currents to ground, vertical pump motors need something more.

Some carriers conduct electricity, and it is convinced that a carrier should be electrically isolated, disconnecting the motor from the pump shaft electrically though not mechanically. In addition to protecting the motor’s thrust bearing from electrical damage, this keeps shaft currents from jumping to the bearings of the pump itself, or to the bearings of a gearbox, tachometer, encoder or other component.

Carriers fabricated from inferior metals, inappropriate coatings or application protocols that fail to provide long-lasting protection won’t work. To apply the ceramic coating, IEMCO uses a tightly controlled flame-spray welding procedure. To minimize subsequent wear on the coated surface, proper bearing fit is of the utmost importance, so Wilkins’ team grinds each newly coated carrier to very tight tolerances. The finished carrier has a hardness of Rockwell 50C and provides a resistance of more than 1 gigohm at 1,000 volts. The National Electrical Manufacturers Association (NEMA) standard for carrier isolation is only 1 megohm at 500 volts.

Linqing Nine Star Bearing Science & Technology Co., Ltd            

(Insulated bearing, Hybrid ceramic bearing and  Brass cage DGBB)

Follow us via E-mail info@jxkjzc.com; Website www.ninestarbearing.com.