# VFD question



## TRurak (Apr 10, 2016)

I've got a 3HP 460volt 3 phase TEFC motor on an industrial air purifier. It shipped with a VFD and I've never wired a VFD before. I'm feeding this off of a bus duct. Aside from the normal OCP (fuses in the bus duct switch), and a non fusible disconnect next to the unit, are there any special requirements for protecting a VFD?


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## glen1971 (Oct 10, 2012)

Controls or interlocks to the drive from your Control System?

No disconnect between the VFD and the motor, unless it is properly interlocked..


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## TRurak (Apr 10, 2016)

The drive has the controls built into it.


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## Cow (Jan 16, 2008)

glen1971 said:


> Controls or interlocks to the drive from your Control System?
> 
> No disconnect between the VFD and the motor, *unless it is properly interlocked.*.





TRurak said:


> The drive has the controls built into it.


What glen is saying is if you install a disconnect between the drive and motor, it is a VERY good idea to install a disconnect with aux contacts that open slightly before the disconnect opens the 480v and close slightly after the disconnect closes the 480v. You do NOT want someone able to open/close a disconnect on a drive that is trying to run without aux contacts. Slamming that disconnect on into a drive that is already running is the kiss of death.

The aux contacts in the disconnect are used to enable/disable the VFD run signal, the drive will stop running right before you open the disconnect and then resume running after you close the disconnect. 

Hopefully that makes sense?


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## micromind (Aug 11, 2007)

Something will need to start it, stop it and control its speed. This can be the keypad or a remote control. It's possible that the unit it's installed on can control it.

You'll also need to program the motor info if it's not already done. Sometimes factories will do this, often they don't. 

If the motor info is not programmed then the rest of it isn't programmed either. 

Also, never apply any sort of voltage to the output. If, for example, a motor is meggered while connected to the drive, it'll burn up the output transistors. If you apply 480 to the output, it'll blow up. 

A lot of drives want you to install fuses that will blow faster than normal. The manual will specify which ones are acceptable but a lot of us use normal ones anyway.......

If you need help programming, let us know the make and model, several of us around here can guide you through it. It seems horribly complicated but for what you're using it for, it's actually pretty easy.


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## TRurak (Apr 10, 2016)

The company my customer bought the unit through is coming to program it. I installed it this morning. Disconnect to vfd to motor. Thanks for all the help.


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## glen1971 (Oct 10, 2012)

TRurak said:


> The company my customer bought the unit through is coming to program it. I installed it this morning. Disconnect to vfd to motor. Thanks for all the help.


If you have the chance, hang out with the vendor as they program it, and ask questions.. It'll help you when the day comes to troubleshoot!


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## chknkatsu (Aug 3, 2008)

yes there is a control board built into it. but that control board isnt what tells the VFD to turn on or off


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