UL98 switch & motors

[megloff11x]

Reading the scope doesn't answer my question and I'd rather not pay UL $1000 for another of its "short books."

Is a UL 98 listed fused switch suitable as a disconnect for an enclosure containing primarily VFD type motor controllers and a PLC?

I can't find a UL 508 listed switch big enough for the system.

Matt

 

[davidr43229]

Per UL508A table SB 4.2, you can use a fused UL98 Switch and probably meet UL508A. What size drive / hp/ amperage?

 

[jim dungar]

UL508 deals with a switch "directly" controlling a motor, which requires the switch to be rated for making inrush current and breaking locked rotor current. A main switch for a control panel does not typically directly control a motor. A UL98 switch feeding a VFD definitely does not act as a motor controller because it never needs to break the LRA of the motor.

 

[megloff11x]

Thanks. It's actually a system with four servo motors and servo drives (PWM output - same as a VFD), a PLC, and some other extraneous stuff. The motors and drives are rated for up to 30A each or a total of 120A (they're foreign made and follow no coherent specifications that I can translate simply into NEC-esque). My door switch choices jump from 100A to 200A, so I'm going big.

My concern was that the UL98 listing would be inapplicable.

Matt