VFD is a disconnect

[local401]

I have a VFD mounted for a pump It has no breaker , but it does have a off switch . Does the VFD need a disconnect also ? The panel that feeds the VFD is in a electric room and is around the corner. The voltage is 480

 

[DLTravis]

I have a VFD mounted for a pump It has no breaker , but it does have a off switch . Does the VFD need a disconnect also ? The panel that feeds the VFD is in a electric room and is around the corner. The voltage is 480

Article 430.103 states "The disconnecting means shall open all ungrounded supply conductors..." If the off switch is simply a control voltage switch you need a separate disconnect. However, if the off switch meets the requirements of 430 IX you do not need an additional disconnect.

 

[John Valdes]

It is not necessary to have a disco. But you must have a breaker or fuses (I recommend semiconductor fuses) protecting the drive. Some will just install a non fusible disco at the drive for maint. and troubleshooting.

Make sure you install a line reactor on the line side of the drive. This cleans up the power some and knocks down spikes that could trip the drive.

Check line / load reactors at < www.tci.com > < or www.baldor.com >

Note: Use caution with motor connections when the drive is stopped. Some vector drives produce current in a stopped motor for shaft locking. Turn off the supply when working with the motor.

 

[rick hart]

It is not necessary to have a disco. But you must have a breaker or fuses (I recommend semiconductor fuses) protecting the drive. Some will just install a non fusible disco at the drive for maint. and troubleshooting.

I am not sure I agree with this. A service disconnect is required for a motor controller and a drive certainly qualifies for that. 430 Part IX.