Thread: Can a VFD be wired with plugs?

The motor and VFD should be hard wired, especially on a DC since it is under considerable load when the motor is running. Compare that to a drill press or lathe that is really only under load when drilling or turning.

Disconnecting the motor and VFD is possible if the motor is not running (VFD can still be on), but if you forget to turn the motor off using the VFD first, you risk damaging the motor and VFD.

My guess is you have a 3P contactor type switch on the DC. This must be removed as these usually have a current limiting device to prevent the motor burning out. If this ever activates while the motor is running (which is usually when its activated) the contactor will disconnect the DC motor from the VFD and there will be a loud BANG and smoke from the VFD.

In practice it's just safer if all switches between the VFD and motor are removed. The VFD will automatically replace the function of the contactor's current limiting device provided the current limit parameter is set correctly in the VFD.

If you want to retain the contactor switch the VFD must be after the contactor ie in between the contactor and motor.

There are smart ways around all this but they require more fiddling than a 'hard wire".

Use of a VFD for multiple machines is high impractical - sounds like you need to read the first post in the electronics forum (VFDs for Newbies)

Thanks for a very detailed reply, they all sound like good reasons to not do it!

The 240V input to the VFD can certainly be wired with a plug but as Bob says you would need to remove or bypass whatever 3 phase controls are between the 3 phase plug and the motor.
Definately doable but might take a bit of mucking around depending on whats there now. You would also need to check that the motor is VFD compatible without modification as you will be running it at a different voltage. Some photos of whats there will help.

Not sure if this helps, just a screenshot from the advert I bought it from

Thanks everyone!

dusty1.jpg

dusty2.jpg

That DC name plate says it requires a neutral which VFDs normally got use.
Does that mean it has some kind of 240V SP shaker or filter cleaner built into the DC ?
In that case that would need to be wired separately - ie outside of the VFD.

However, are you sure it's 2.2kW, that nameplate says 7.5kW although the current rating says 5.5A which suggests a 2.2kW.
7.5kW is equivalent to 10HP which is well above the limit of 240V SP VFDs which is about half that

That label may refer to the switch that it is on. K&B make motor switchgear.

Hi BobL, I am very confident it is 2.2KW, here are the specs of the current machine, I doubt much has changed on mine.

New 2016 felder AF22 2 Bag Dust Collectors in EMU PLAINS, NSW

Thanks!

Uberlastschutz is overload protection so it looks like it has a thermal O/L and either a load break switch or a switch and contactor but there doesn't seem to be enough room for a contactor. If there is thats why it needs the neutral. You would need to ditch all that stuff and connect the VFD to the motor but only if it can be wired in Delta or you use a 415V output VFD.

Originally Posted by NCArcher

. . . . . . but only if it can be wired in Delta or you use a 415V output VFD.

To be a little more specific . . . .
A 240V output VFD will only work if the motor is already wired as a Star and can be rewired as a Delta.
If it's already a delta then a 415V output VFD will be required.

Thanks for all of your very detailed advise, was wondering if I opened up the switching/junction box and took a photo of the wiring, could that help identify a star/delta wiring? Not chasing anything definitive, but would be a helpful starting point along my VFD journey!

Thanks again, Steve

Steve, the motor data plate should have that information on it, take a photo and post it here.

263214114_319864439959232_5550567053661672302_n.jpg

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Hi found this sticker next to the motor mount, hope it might mean more to you guys than it does me!

Ta, Steve

Steve, I am not an electrician but it looks like that motor can be run off 240V three phase or 415V three phase and the choice is yours. Give me a call if you want, I have to go to Robertson MS on Saturday and we might be able to arrange something.