need VFD recomandation

[MightyM7]

Hi there,

excuse please but this is not directly a CNC question but since here are a lot VFD pros I try it (otherwise please move the thread).

I've a belt grinder which I currently use at fixed speed with 380V. It seems that the belt grinder is also capable of 220V. See specs:




In future I like to use it with 220V and I want to adjust belt speed. Now the question:

Which VFD do you recommend? Can I use this one:

https://de.aliexpress.com/item/Varia...616549715.html


Thank you very much.

Regards, Mighty

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[EPTech]

You need to be careful when putting old motors on a VFD. They were not built with regards to VFD. Their windings can heat up when used on a VFD.

If you plan on using it on 220V single phase, you need to select a single phase input VFD like the one you suggested. You also need to put the motor in delta (220V) configuration. Make sure you put 220V in the drive parameters as the rated motor voltage. The drive will lower the voltage accordingly to prevent overheating of the motor at low frequencies. I do not recommend using voltage boost in this particular case, again to prevent over-heating. Also do an auto-tune, if possible, so the drive can measure the stator resistance and inductance.

Happy inverting, no heating up
Pascal.

[EPTech]

Oh yes,

I do not recommend more than 25% over-speed, since the motor (and machine) is not mechanically built for this IMO.

[MightyM7]

Thank you very much for your reply. I do not plan to use it for overspeed. I need lower rpm.

Would it be better to use it at 380V with a vfd to lower the rpm?

Thanks in advance.

[mactec54]

Thank you very much for your reply. I do not plan to use it for overspeed. I need lower rpm.

Would it be better to use it at 380V with a vfd to lower the rpm?

Thanks in advance.

If you already are running it on the 380v then there would be no point to run it on 220v, ( 380v is more efficient than 220v ) the only thing you have to watch for is when running it slower that it gets enough cooling, as the motor fan becomes inefficient as you run it slower, if you notice the motor getting hotter, then add an electric fan to cool the motor

[MightyM7]

If you already are running it on the 380v then there would be no point to run it on 220v, ( 380v is more efficient than 220v ) the only thing you have to watch for is when running it slower that it gets enough cooling, as the motor fan becomes inefficient as you run it slower, if you notice the motor getting hotter, then add an electric fan to cool the motor

I see. I've 380v in my garage but with 220v vfd (input) I could also use it at my friends garage.

So possible solutions are:

a) use 220v as input for the vfd and also for the motor.
Since I used it with 380v, do I have to change something at the motor?

b) use 380v as input for the vfd and also for the motor
Here I have to look for the temps at lower rpm.

c) use 220v for input to the vfd, and use a 220 ->> 380 vfd.
These vfds seem to bemuch more expensive.

Hm, what should I do?

Thanks. Mighty

[EPTech]

Hi there,

The speed on induction motors should be altered by altering the frequency, not the voltage. If you lower the voltage, the motor will lose power and start turning at a lower speed but that will also mean the motor is slipping and this will increase it's current dramatically and it will start to heat up. When using a 220V VFD I would put the motor in delta (220V). The VFD will lower the voltage at low frequencies to prevent overload anyway. If you want to play with the voltage, I would adjust the VFD and leave the motor in delta. If you connect the motor in Y (380V) and your VFD only has 220V output, it will greatly reduce power.

Pascal.

[mactec54]

I see. I've 380v in my garage but with 220v vfd (input) I could also use it at my friends garage.

So possible solutions are:

a) use 220v as input for the vfd and also for the motor.
Since I used it with 380v, do I have to change something at the motor?

b) use 380v as input for the vfd and also for the motor
Here I have to look for the temps at lower rpm.

c) use 220v for input to the vfd, and use a 220 ->> 380 vfd.
These vfds seem to bemuch more expensive.

Hm, what should I do?

Thanks. Mighty

It does not matter what voltage you chose to run it on, you still have to watch low RPM for any heating of the motor, as the motors fan gets slower it cools less, this has nothing to do with what voltage you use

If you want it to be universal then go with 220v, you will have to change the way it is wired in the motor, under the electrical cover on the motor it may show you how to change the connection for 220v

[Arjay]

c) use 220v for input to the vfd, and use a 220 ->> 380 vfd.
These vfds seem to bemuch more expensive.

Do you have a link to a 220 -> 380v VFD? I was looking for this a short while back and was unable to find a VFD that stepped up 220 to 380v within the VFD.

[MightyM7]

Do you have a link to a 220 -> 380v VFD? I was looking for this a short while back and was unable to find a VFD that stepped up 220 to 380v within the VFD.

Of course: https://de.aliexpress.com/item/VFD-5...OrigTitle=true

Regards, Mighty

[Arjay]

Of course: https://de.aliexpress.com/item/VFD-5...OrigTitle=true

Regards, Mighty

Thank you.

[EPTech]

I see. I've 380v in my garage but with 220v vfd (input) I could also use it at my friends garage.

So possible solutions are:

a) use 220v as input for the vfd and also for the motor.
Since I used it with 380v, do I have to change something at the motor?

b) use 380v as input for the vfd and also for the motor
Here I have to look for the temps at lower rpm.

c) use 220v for input to the vfd, and use a 220 ->> 380 vfd.
These vfds seem to bemuch more expensive.

Hm, what should I do?

Thanks. Mighty

That is way to complicated. Keep it simple. Just get a 1-1.5kW VFD with a single phase 220V input. Just use it on single phase all the time. Put the motor in delta (220V) and that's it. Additionally, if you are planning to run at low speeds all the time, you could get a fan. Since the motor does not have cooling ribs, I recommend putting a tube around the motor and placing the fan in the tube, if you have the space for that of course.

Happy inverting

[MightyM7]

Thanks again for your answer. Just one point is not clear:

Put the motor in delta (220V)

Does this means I've to change something at the motor? Inside? Is 380V always in 'not delta'?

Regards, Mighty

[EPTech]

Thanks again for your answer. Just one point is not clear:



Does this means I've to change something at the motor? Inside? Is 380V always in 'not delta'?

Regards, Mighty

On your motor name plate it says 380/220V. That usially means 380V in star or 220V in delta. Your VFD will be 220V input 3x220V output. So you need to put the motor in delta (220V) mode for it to work with adequate power. If you leav it in star or Y (380V) mode the power will be reduced. If you open up the motor terminal box you will usually see 6 terminals marked U1, U2, V1, V2 and W1, W2. When used in star, there will be copper strips across W2, U2 and V2 (horizontally). You want to place the motor in delta, so you want to remove the strips. If you are lucky, two of the three terminals will have 2 strips across them so you will end up with 3 strips. If not you will have to make one extra yourself or use a wire. You need to place the strips vertically over the terminals so you end up connecting U1 to W2, V1 to U2 and W1 to V2. Your incoming wires remain as before. But try to always connect to the U1, V1 and W1 side to avoid confusion in the future.

DO NOT connect your motor to 380V again after doing this as it will burn!

If the terminals are not clearly marked, take a picture, undo all wiring and strips, so you are left with only the motor wires going to the terminals. Beep out the windings to discover how they are hooked up to the terminals.

Sometimes there is a schematic on the inside of the terminal box, usually on the lid.

If the motor has more than 6 terminals it is likely a multi speed motor. In that case I would advice you to leave it alone and get someone who knows motors.

[MightyM7]

Thanks, thanks, thanks. That's something I can deal with. I'll try to open the motor. May be I put some pictures here if it's not 100% clear to me.

Regards, Mighty