VFD

[Alwayslearningelec]

If a motor has a VFD would is also have a disconnect or starter? Thanks.

 

[richwaskowitz]

Not always

Not always

We use VFDs all the time for conveyors and some have safety disconnects at the motor and some are before the drive. It depends on the customer. We rarely provide starters for overload protection or control with VFDs anymore. Again, only when the customer requires it.

 

[augie47]

You may want to look at this:

http://forums.mikeholt.com/showthread.php/115993-VFD-disconnect-question?highlight=drive

 

[Alwayslearningelec]

Sorry guys what I meant is can there be a separate starter and a separate disconnect for a motor or would it always be a combo starter disconnect? Thanks.

 

[augie47]

either is NEC acceptable

 

[Alwayslearningelec]

either is NEC acceptable

So you can have a separate starter and a separate disconnect on a motor? THanks,

 

[Alwayslearningelec]

We use VFDs all the time for conveyors and some have safety disconnects at the motor and some are before the drive. It depends on the customer. We rarely provide starters for overload protection or control with VFDs anymore. Again, only when the customer requires it.

Thanks.

 

[Rick Christopherson]

You don't normally have a motor starter or disconnect with a VFD (at least downstream from the VFD). This is because the VFD does not like it when the circuit is broken between the VFD and the motor. The VFD itself is the starter, and the disconnect should be upstream of the VFD where possible.

 

[don_resqcapt19]

The code requires that you have a disconnect for the motor controller and for the motor itself. In this case the motor controller is the VFD and there must be a disconnect within sight from the VFD. The code also requires a disconnect within sight from the motor, but there are some exceptions that will permit the remote, lockable controller disconnect to be used in lieu of a disconnect within sight from the motor.

 

[iwire]

You don't normally have a motor starter or disconnect with a VFD (at least downstream from the VFD). This is because the VFD does not like it when the circuit is broken between the VFD and the motor. The VFD itself is the starter, and the disconnect should be upstream of the VFD where possible.

We work at one industrial location and they still place disconnects on the load side of VFDs but the disconnects are equipped with an auxiliary early break contacts that shut the VFD down if the disconnect is operated.

 

[petersonra]

So you can have a separate starter and a separate disconnect on a motor? THanks,

You can have ten separate starters and ten separate disconnects all in series on the same motor if you want. or you can have a single starter and disconnect in the same enclosure.

Think of a VFD as a fancy starter.