4 wire twist lock plugs VFD

Greenberg Woods

Greenberg Woods

Joined
Dec 27, 2013
Messages
2,665
Hey guys, sorry to be asking so many questions. I talked to H HSC /// and he suggested i use 4 wire twist lock plugs so i can use my grinder and disc off the same VFD. ive bee nreading about them, but im still a little confused.

I read through this thread http://www.bladeforums.com/threads/advice-for-setting-up-vfd-wiring.1492591/

But here is my understanding so far.

I would get 1 male https://www.mcmaster.com/#7164k46/=17mxoo6 and wire it into the end of the out cable on my VFD.

I would get 2 female and wire one into each motor, one for the belt one for the disc and would use that to switch between the two.

Anything im missing?
 
That is how I have mine wired, for the disc grinder, I have two sets of plugs - one for forward, and one for reverse.
 
I think you have one thing backwards though. You want the female on the vfd and the male plugs coming out of the motors. Otherwise if you accidentally have the vfd powered up you could get electrocuted if you have a male plug coming out of the vfd that has live power and nothing hooked to it.

Edit: also id recommend getting a vfd that has built in reverse if you want it. At about $30 a plug or outlet for 4 wire twist locks having a plug for forward and reverse on just 2 machines would be $60 plus for the extra plugs. But that's just MHO. You're really not saving any money doing it like that unless you can get the plugs for cheep.
 
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Yeah thats right, I do have mine with the female on the VFD.

As for the forward/reverse - if you have the VFD wired up to the motor, and switch any pair of the U,V,W wires - it will go in reverse
 
avs3323 said:
Yeah thats right, I do have mine with the female on the VFD.

As for the forward/reverse - if you have the VFD wired up to the motor, and switch any pair of the U,V,W wires - it will go in reverse
Click to expand...

Yes a 6 lug 2 way 30 amp switch would make easy work if that. Better than undoing wire nuts and switching wires. Probably cost less than $10.
 
avs3323 said:
Maybe someone else can answer - I use these, and run a wire from the motor frame to ground - is that ok?

https://www.amazon.com/Leviton-620P...&qid=1498876213&sr=8-5&keywords=250+volt+plug
Click to expand...

They will work but you get a better connection with a twist lock plug. I personally wouldn't use them. I'd rather have a plug rated at a higher amperage. Twist locks are much safer at higher amperage. The straight prongs can get loose and if that plug only makes contact with a small part of the prong it can create heat and then the potential for a fire from melting plug and or wires. That's why dryers and ovens have such large prongs on the plugs.
 
avs3323 said:
Maybe someone else can answer - I use these, and run a wire from the motor frame to ground - is that ok?

https://www.amazon.com/Leviton-620P...&qid=1498876213&sr=8-5&keywords=250+volt+plug
Click to expand...
Your description seems as if this is connecting your VFD to motor ??
If so, please dont !!

To connect 3phase motor to VFD,
Use an appropriate 4 wire plug & receptacle. Such as the NEMA L15-20 referenced prior.

This NEMA 6-20p from Amazon is only suitable for single phase 20amp 240vac. Such as what may connect your VFD to mainspower.
 
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Yes, they are 'different'.
Each wire represents one of the three phases of the VFD output.
(Or three phases of the motor input)
Without 'tech documents for the VFD, the only way to tell them apart needs a phase sequence detector. But for the purpose of connecting a beltgrinder, its not important.
Assuming your motor is configured to match the VFD output voltage, It really wont matter what sequence they connect to the 3 wires which exit the motor. The only thing happens if they are connected "wrong", the motor spins opposite direction than what you wanted.
To change direction, reverse connections on any two of the three wires. It wont matter which two.
Or,, if VFD has reverse feature, just flip 'fwd-'rev switch !!

(Obviously, the "equipment ground" fourth wire is a separate topic...)

Btw, I mention "for the purpose of a grinder". Its not critical if its hooked up by trial & error. If its done backwards, simply change it.
But some machines cant be accidently started in reverse. Rotation must be known and connected correctly before switching on.
 
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Greenberg Woods said:
Hey guys, sorry to be asking so many questions. I talked to H HSC /// and he suggested i use 4 wire twist lock plugs so i can use my grinder and disc off the same VFD. ive bee nreading about them, but im still a little confused.

I read through this thread http://www.bladeforums.com/threads/advice-for-setting-up-vfd-wiring.1492591/

But here is my understanding so far.

I would get 1 male https://www.mcmaster.com/#7164k46/=17mxoo6 and wire it into the end of the out cable on my VFD.

I would get 2 female and wire one into each motor, one for the belt one for the disc and would use that to switch between the two.

Anything im missing?
Click to expand...
I would use a female wired to VFD and males to motor. typically the source is female, user is male. think your house, the wall has female receptacles, your appliances have male plugs
 
Greenberg Woods said:
Hey guys, sorry to be asking so many questions. I talked to H HSC /// and he suggested i use 4 wire twist lock plugs so i can use my grinder and disc off the same VFD. ive bee nreading about them, but im still a little confused.

I read through this thread http://www.bladeforums.com/threads/advice-for-setting-up-vfd-wiring.1492591/

But here is my understanding so far.

I would get 1 male https://www.mcmaster.com/#7164k46/=17mxoo6 and wire it into the end of the out cable on my VFD.

I would get 2 female and wire one into each motor, one for the belt one for the disc and would use that to switch between the two.

Anything im missing?
Click to expand...
I agree with the plug choice.

Female from the VFD, ,not male - supplying power just like the wall
Males for the motor, just like plugging a toaster into the wall
They do it that way so you can't lick the live power.


Ground wire to the ground pin, the other three wires to the other three pins - no special order


Install the switch to reverse, it's cheap, simple and handy.

I have photos of all this, but photobucket is unreliable right now.
See the VFD section of my standard reply and see if there are direct links there.

Reverse switch is single pole double throw using the jumper spades built in, read the manual and see my photos
Look at the photos of the KB sold switches.
 
Ben, you can get a reversing switch to add onto your VFD for about $20

male plug from your motors

4gFa5Jm.jpg
 
I use 30amp dryer outlet male plugs ($8) and female outlet ($12) versus the twist locs that are about $40 each. Below is my set-up:

 
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