Pump Driver Options

As with most mechanical drive applications, ac electric induction motors predominate, particularly in smaller capacities. Speed control can be accomplished with a dc motor, a multiple-speed ac motor, or by equipping an ac motor with a variable frequency drive (VFD). VFDs can control speed precisely over a wide range of operation,

Fig. 31-28 3,500 rpm Pump Performance Curves. Source: Bell & Gossett
Fig. 31-29 1,700 rpm Pump Performance Curves. Source: Bell & Gossett

typically from 40 to 100% of full load. While far less costly and easier to install than prime mover drives, VFDs do not provide electrical demand savings during operation at full speed.

Under certain circumstances, investment in prime mover drives is justified on a life-cycle economic basis or by the need for backup in the event of an electric service outage. Along with the ability to provide speed control, prime mover drives provide electrical demand savings and the potential for heat recovery. Pumps may also be pneu-

Fig. 31-30 1,170 rpm Pump Performance Curves. Source: Bell & Gossett

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