VFD and INV DUTY

D

Dale001289

Senior Member
Location
Georgia
The subcontractor wants to implement a standard 50hp squirrel cage, 3phase motor with type F insulation on the output side of a VFD
The motor name plate and data sheet does not state inverter duty anywhere.
And the cable they want to use is standard TC-ER without a shield has one EGC. At least it will be routed in steel conduit, then transitions to steel cable tray
Is this going to be a problem?
 
If not inverter duty motor at least put a line reactor on output side of drive. This more important the longer the length of conductors between drive and motor. More critical for 480 volts than 208-240 as a general rule.
 
Class F insulation is the standard insulation I have seen on any inverter-rated motor I have installed, BUT they always tend to also explicitly say that it is in-fact rated for inverter duty.

As for the lack of shielding: that is not so much for the VFD or the motor it powers, but for "protecting" any nearby circuits from any induced noise from the VFD output conductors (essentially the shielding is acting as more of a faraday cage for the VFD output conductors). The conduit runs should be fine as long as the conduit is not being shared.
The cable tray runs might be a bit of an issue if they are going to be sharing the tray with anything more sensitive like control cables, or the trays holding the VFD output conductors will be run parallel to some other trays with more sensitive circuits in them.

Can you provide the make & model of the motor they plan to use? And is the cable tray the steel basket style tray?
 
kwired said:
If not inverter duty motor at least put a line reactor on output side of drive. This more important the longer the length of conductors between drive and motor. More critical for 480 volts than 208-240 as a general rule.
Click to expand...
Kwired why will the load side reactor assist? They do have a filter on the load side of the VFD
 
Dale001289 said:
Kwired why will the load side reactor assist? They do have a filter on the load side of the VFD
Click to expand...
will smooth out the waveform which if dealing with 480 volts can have voltage peaks of 1200 volts. Then there is IGBT reflected wave issues that get worse as conductor length gets longer. Is generally recommended to use a line reactor even with an inverter duty motor if the conductor length is over 50 feet, particularly if operating volts is 480 volts.

Maybe take a look at this page, it explains some of this better than I can.

Is this filter you mention an RF filter or a line reactor?
 
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