240-250 V 380-440V on a 3/4hp 3 phase motor

[daleyd]

If you go too big on the vfd you may not be able to set the current limit at the motor plate value - a couple of sizes up is usually no problem but if you go too large then it may be. In the event of a fault as you are relying on the drive to limit the current you can end up cooking your motor if not careful, you may think this may not be an issue for your particular application (eg if you are always present when it’s running so you would notice if it is stalled etc) or you can put an overload in line if needed (usually done of using a big vfd on multiple smaller motors).

 

[Kram]

It currently has 3 wires on the N post, its wired in wye(star), but you need delta. Each of the 3 windings has one end on the N and one to a connection. You need a meter to check which is for which winding and put the return onto the next post. Ignore the lines in the pic below, but note the lables u1,u2,w1,w2,y1,y2 and how one goes to the next. Modern motors have the connection box set out like below so its simpler to swap.

 

[Sean64]

Thanks Kram

 

[Sean64]

So is a 3hp vfd too big for the 3/4 hp motor

Sean

 

[daleyd]

So is a 3hp vfd too big for the 3/4 hp motor

Sean

If you have a manual you can see what the current limit setting will go down to, if you can set this down to what your current is on the motor plate at 230v operation then you are good to go.

It’s also absolutely not 100% necessary to set the current limit the same as the motor plate, it’s just good precaution as that way you reduce the risk of damaging the motor in the unlikely event of a fault occurring. The level of risk is up to you to decide, it’s just something you should be aware of when purchasing.

 

[Kram]

1.5kw is 2hp, 2.2kw for 3hp.
I wouldnt have gone any smaller.
From the photo looks like an Nflixin 9100
Manual here

Product information download – NFlixin

nflixin.com

 

[Sean64]

Is this correct , , which terminals do I connect the vfd to . I don't do wiring plus I'm colour blind ...

Sean

 

[carbon]

Ideally you need a four core cable so you can earth the motor. But it doesn’t really matter which way you connect the wires. If it spins the wrong way when you have your vfd just swap two of the phase wires to change the direction

 

[daleyd]

As long as the 2 connections internal to the motor on each post are correct then the external wires can go anywhere, as said above if direction is wrong swap 2 of the external wires (or reverse on the drive itself). Also as @carbon said it’s not a great idea to use the green/yellow as a conductor but if you just want to do a quick test then ok, just try to make sure the motor is out of the way as it’s not currently earthed.

 

[Sean64]

Ideally you need a four core cable so you can earth the motor. But it doesn’t really matter which way you connect the wires. If it spins the wrong way when you have your vfd just swap two of the phase wires to change the direction

Chang the cable on the VFD ? or the motor ?

 

[Kram]

Colours may be indicating each winding so you'd want two different colours to each post before the external wires.

From vfd to motor, get a length of screened 3+earth SY cable. The screen should be connected to earth only at one end and the other end not connected.

Even for testing, you need to earth the motor. If there were a fault then the whole machine could go live. Use a seperate cable if you have to.

 

[Sean64]

Happier now guys

 

[carbon]

Earth needs to go to the earth point on the case not the ‘N’ connection

 

[daleyd]

The N terminal isn’t the earth, you need to connect a wire from the vfd earth to the terminal with 3 lines on the top right.

 

[daleyd]

Is the motor attached to the machine or just sitting on a bench? If it’s on the machine then for sure you need the earth connecting (you should always have it connected, at a push I’ve done without it but only if it’s well out of touching distance and on an insulated mat and only then for a very brief test. If you are not confident in your electrical knowledge and set up then you shouldn’t even be contemplating this)

 

[Sean64]

Sorted now ,this is what happens when blithering takes place .

 

[daleyd]

I don’t want to sound like a moaning Minnie but that earth also needs some sleeving, you don’t want that touching a live terminal!!

 

[Sean64]

Is the motor attached to the machine or just sitting on a bench? If it’s on the machine then for sure you need the earth connecting (you should always have it connected, at a push I’ve done without it but only if it’s well out of touching distance and on an insulated mat and only then for a very brief test. If you are not confident in your electrical knowledge and set up then you shouldn’t even be contemplating this)

But how do you build up confidence . I've had you guys helping me this afternoon otherwise I wouldn't be doing it . I'll probably be back tomorrow when the VFD arrives ,so make sure you have your tea and biscuits at the ready

 

[daleyd]

But how do you build up confidence . I've had you guys helping me this afternoon otherwise I wouldn't be doing it . I'll probably be back tomorrow when the VFD arrives ,so make sure you have your tea and biscuits at the ready
I kind of meant that if your not 100% confident then you shouldn’t take any shortcuts - I’ve done it (run without an earth, as a test) because it got me out of a hole and I was absolutely confident it was safe, there was no way anyone would be able to touch the motor.

The fact that you weren’t sure what the earth was is no fault of yours but shows that you have some way to go - and as the motor is on the machine then you can’t take any chances, I had incorrectly assumed the motor was sitting out on a bench. There’s nothing magical or particularly difficult about any of this but you’ve done the right thing by asking for advice and making sure it’s done safely.

 

[My Old Landy]

For your remote panel you may consider buying an off the shelf solution or building your own like I did: