Tech Tip

VARIABLE FREQUENCY DRIVES

Care should be used when applying an inverter in a multiple motor application.
 

  • Motors must be the same HP, Nema design, RPM, frame and voltage rating and preferably from the same manufacturer.
     
  • Never switch a motor on and off from the output of a drive without first stopping the inverter.
     
  • An output line reactor is recommended to help minimize the effects of multiple motors using one drive. Refer to the drawing for placement of the line reactor.
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  • The inverter should be sized by totaling the FLA of the motors and multiplying by 1.1, then selecting a drive that has a rating that meets or exceeds this FLA.
     
  • Each motor must have its own thermal overload relay and branch circuit protection (NEC Code).

VACdrive (orig.-8/1/02)