Thread: Idiots Guide To VFD/VSD

You're not the only confused idiot. I've been trying to follow the threads, but I having no electrical background or learning - I'm stuffed.

So, I'll join you.

I don't have much experience with motors but I do have experience at being an idiot.
So here it goes...

I'm not sure that you really need to understand too much of the electrical side.
From what I can see in the photos this is a 4 wire motor that allows for single phase (240v), 2 phase (380v) and 3 phase (440v).
To connect it single phase you will only need be one active and a neutral connection (still make sure it is earthed).
I can't quite make out the schematic or the finer text on the picture to give any details on how to do that.
Is it possible to get more detail in the picture?

Originally Posted by knucklehead

I can't quite make out the schematic or the finer text on the picture to give any details on how to do that.
Is it possible to get more detail in the picture?

Yep ..... but tomorrow if that is alright. Unfortunately too cold to go outside

Originally Posted by knucklehead

I don't have much experience with motors but I do have experience at being an idiot.
So here it goes...

I'm not sure that you really need to understand too much of the electrical side.
From what I can see in the photos this is a 4 wire motor that allows for single phase (240v), 2 phase (380v) and 3 phase (440v).
To connect it single phase you will only need be one active and a neutral connection (still make sure it is earthed).
I can't quite make out the schematic or the finer text on the picture to give any details on how to do that.
Is it possible to get more detail in the picture?

KH

In connecting the motor for single phase I would presume it will lose much of it's torque and consequently not really perform as well as if it were connected in three phase. Is this correct?

A VFD question of my own. During speed reduction is there a loss in power or does this depend on the sophistication of the electronics?

Regards
Paul

Originally Posted by Sir Stinkalot

The more I think about it the better off I think I will be just swapping out all of the 3 phase gear to a new single phase motor.
Confused Idiot Stinky

Sir Stinky

I have done exactly that with a jointer (much smaller than yours) and a lathe. On each occasion I went up a little in power. The lathe from 1hp to 1.5hp and the jointer 1hp to 2hp.

It is my impression that the three phase motors have much more torque than the same hp single phase motor. Please don't ask me how they can be the same hp. I have no idea.

Also note that a 1hp 3ph motor is likely to be smaller than it's single phase brother. Probably not too much of an issue on a jointer, but on the lathe I converted I had to make room!

However, I do see the conversion to single phase as the "easy" way out. I would like to go down the VFD path for my next conversion. I am interested to hear some comments.

Regards
Paul

Originally Posted by Bushmiller

However, I do see the conversion to single phase as the "easy" way out. I would like to go down the VFD path for my next conversion.

From my limited understanding with the VFD/VSD (is there a difference?) I think you can control the speed. On a lathe I can see this being handy but less so on a jointer.

I have read that changing from 3 phase to single phase you should go up approximately 1hp. The jointer is currently 3HP so I would need to go 4HP in a single phase. A 3hp single phase is around $250-$300 and a 4hp $450. Its a fair difference in price.

I don't ever see myself using the full capacity of the jointer so I might be able to get away with the 3hp single phase. My quick look at it tonight would indicate it is quite easy to swap out the motor.

Originally Posted by knucklehead

From what I can see in the photos this is a 4 wire motor that allows for single phase (240v), 2 phase (380v) and 3 phase (440v).
To connect it single phase you will only need be one active and a neutral connection (still make sure it is earthed).
I can't quite make out the schematic or the finer text on the picture to give any details on how to do that

Maybe I've missed something, but I think you are confusing the starter and the motor. The starter can start a single or multi-phase load, but that doesn't mean the motor can be run off any of the combinations mentioned (other than 415 as stipulated on the motor nameplate).

SS, you need to determine if the motor can be changed to run 240V 3 phase rather than it's current 415V 3 phase. Can you provide a picture of the terminal block on the motor?

Vernon is correct on this one. You cannot run the motor on single phase.
We need to see inside the motor terminal box to see if it has 6 wires coming from the motor windings. If it can be easily configured to run from a VSD it may not be any cheaper than a new single phase motor for that size VSD. Although i haven't purchased one for a while and the VSDs are getting cheaper and cheaper.
Make sure the single phase motors you price have the same speed (2800rpm) as the old 3 phase. Also measure the shaft diameter so you can reuse the old pulley.
If you do get a VSD don't worry about setting it up and getting it working. There are plenty of members who can help out.

Originally Posted by ncarcher

.....
If you do get a vsd don't worry about setting it up and getting it working. There are plenty of members who can help out.

Yup

Originally Posted by Vernonv

The starter can start a single or multi-phase load, but that doesn't mean the motor can be run off any of the combinations mentioned (other than 415 as stipulated on the motor nameplate).

SS, you need to determine if the motor can be changed to run 240V 3 phase rather than it's current 415V 3 phase. Can you provide a picture of the terminal block on the motor?

By looking at the motor I am fairly certain it can only run off 3 phase (big old beast). It would be good however if I can reuse the switch with a single phase (if I go that way). I will get some more photos.

I take it that the terminal block is the box on top of the motor? (read I am an idiot).

Originally Posted by NCArcher

We need to see inside the motor terminal box to see if it has 6 wires coming from the motor windings. If it can be easily configured to run from a VSD it may not be any cheaper than a new single phase motor for that size VSD.

Deep down I think it will be cheaper to get a new single phase motor. It also has the benefits of being a new motor with a warranty. Whilst the old 3 phase motor was working I wouldn't want to go down the VSD path only to find I need to replace the old motor because it has died.

Either way as I said earlier it will be interesting just to work through the options and it may help others in the future.

Originally Posted by Sir Stinkalot

From my limited understanding with the VFD/VSD (is there a difference?) I think you can control the speed. On a lathe I can see this being handy but less so on a jointer.

I have read that changing from 3 phase to single phase you should go up approximately 1hp. The jointer is currently 3HP so I would need to go 4HP in a single phase. A 3hp single phase is around $250-$300 and a 4hp $450. Its a fair difference in price.

I don't ever see myself using the full capacity of the jointer so I might be able to get away with the 3hp single phase. My quick look at it tonight would indicate it is quite easy to swap out the motor.

Sir Stinky

VSD and VFD are one and the same. However you need to check that the VFD converts from single phase input to three phase output (ie: to run your 415V motor) as some only vary the speed be it 240V or 415V.

If you go to a 4HP in single phase, your 15amp power point will no longer be adequate. You will need 20amp, which is ok, but in turn it requires heavier wiring and you will need to consult with your electrician. I recently had installed 20amp outlets (flat pin and round pin) with the conversion to large single phase motors in mind, but I have not yet installed anything, although my welder is happy at last!

By the time you are talking 4HP, there is not much difference in cost between the motor and the VFD. Either way you would require the heavier wiring. (Not if you go 3HP 415V and a VFD. 15amp will do there. I think)

I started this post about 3 hours ago and had to head off, so apologies if I am repeating another reply or even worse, I am totally at odds with others.

I am still very interested to hear from the experts.

Regards
Paul

Originally Posted by Bushmiller

If you go to a 4HP in single phase, your 15amp power point will no longer be adequate. You will need 20amp, which is ok, but in turn it requires heavier wiring and you will need to consult with your electrician.

Paul .... I am looking at upgrading the supply to the garage with its own sub board ...... that is if I can find an electrician to come and do the work (another story). I will be looking at running 15amp for the table saw and either 15amp or 20amp for the jointer. I will make sure I confirm everything with the electrician before I purchase anything.

Originally Posted by Vernonv

Can you provide a picture of the terminal block on the motor?

I hope this is the terminal block. Sorry about the photos ..... mix of bad lighting and the Iphone.

There are three connections from the motor (foreground) and then three out to the starter box (yellow/blue/green). The ybg go to the starter box (for want of a better word) at the bottom right, the wires out on the bottom left go to the switch and the top left wires go to the plug.

The starter box is a MEM Autoline Starter (UK Patent) pictures hopefully tell the rest.

If it would be possible to wire a new single phase motor into the starter box that would be great. What does the starter box do? It seems quite complex for just a switch.

The starter is just a contactor and thermal overload, although the TOL is not a type I have seen before. Seems to have actual heater wires to operate the thermal breaking contacts.
You can replace the heaters with a different rating for different motors.
I'm afraid you won't be able to use the thermal overload portion of the starter because the single phase motor will draw a lot more amps than the 3 phase. And good luck getting different sized heater wires.
It will be better to replace the starter with the motor.
More bad news, the motor is wound in star with the star point buried in the windings. While it is possible to extract the star point and rewire it in delta to run from a VSD, IMO it is not worth the trouble, especially for such an old motor.