Help! I've Bought the Wrong Motor

Worrier !!! It looks like a lost battle, best way is to sell it back to some store at a subsidised rate and buy new one.

If it has been bought retail in the UK, then it is not fit for purpose. Take it back to the supplier and get one for the right voltage. They might even be of the same value.

Is there an transformer or something that would correct the voltage?

Yes in principle, though in order to select one the rating of the motor needs to be known.

Do stop worrying! I don't think you have a problem, as long as it has 6 terminals.

It will either be 240v delta, 415v star, or 138v (= 240/√3) delta, 240v star. I've never seen a motor wired the 2nd way, so it's odds-on it's 240v delta, 415v star. Just wire it up in star. Run the 3 incomer phases to 3 of the terminals, and common up the other 3. Then you should be OK.

You won't be able to use star-delta starting, but I expect that's the least of your worries.

Cheers.........Codey

It has three terminals. The rest of what you said was a little greek to me.

OK, a pity, but back to square one!

I've checked to voltages across the 3 phases. One was 420V, One was 185V and the third was 240V. I didn't think that was normal.

Do you mean the 3 phases of the supply? If so it looks very odd. But what do you mean by "across the 3 phases"?

For 415v supply, should be 415v between any 2 phases (420v is well within the tolerance), and 240v between each phase and neutral.

Cheers.........Codey

Between the three phases. The motor doesn'thave a neutral.

I assume you mean the 3 phases of the supply? If so what has the motor to do with it? I'd be surprised if there isn't a system neutral somewhere, but if not an earth point will do the same job as far as voltage measurements are concerned.

The three phases of the suply when measured to earth give me a voltage of 240v, 240v and 78v.

I think I'm going toget an elecy out to sort whatever is going on here. Cheers.

That sounds like a good idea! Maybe buying the wrong motor will turn out to be blessing in disguise if it has highlighted a supply problem.

If there were 2 good phases, 1 bad, that would explain the phase to earth voltages of 240v, 240v and 78v. But you would expect 420v between the 2 good phases, and something lower between either good phase and the bad one, but the same for each. So something strange is going on.

If you do voltage checks at various points on the network, all the way back to the main incomer, you should be able to pin the problem down.

Cheers.........Codey

Did you consult Panasonic?

Worrier

You said that you have 420V, 185V, and 240V line to line.

Also you have 240V, 240V and 78V to earth.

There is no ordinary 3 phase motor that will operate properly on these voltages. Check your voltages again. It is my guess that you have single phase voltage and a neutral that is not grounded properly.

how many horsepower? Then get a delta to delta transformer 240 to 415 that is a little larger.

This looks like a delta connected motor, only 3 terminals. A star connected has 3 + center of star= 4

Not necessarily. If there are 6 terminals, for star connection you wire supply to 3 of them, and common the other 3. Commoning the other 3 gives the star point, but that can be internal to the motor if it only has 3 terminals.

Having said that, I think it's more likely to be delta, see #5.

Cheers...........Codey

This is the spec of the motor. I'm a little confused.

Today, I get L1 to earth 240V, L2 to earth 240V and L3 to earth 68V.

From that, it looks pretty certain it needs 200-240V phase-phase supply. Not sure why they quote the 1-phase voltage. Is that part of the nameplate? difficult to tell from your post.

There seems to be a problem with your supply, but when you sort it, so it's 240V from all phases to earth, it's 415V phase-phase, so motor is wrong.

BTW, did you check further up the supply network, to narrow it down? Can you confirm the phase-phase voltages, as 3 different values looks odd, see my #15.

Cheers......Codey

Did a quick web check and could not resolve the answer properly but are you really sure that its 240volt 3 phase "supply line to supply line" motor or one that would more normally be referred to as 415 volt line-line and have 240 volt across each field.

Your earlier response tells me you do not understand this - so draw two arrows nose to tail, each 240 volts long and bent 60 degrees to each other (that is 120 degrees included angle between them). The long distance between the tail of one and the nose of the other is 415. A 3 phase supply is just a third 240 volt arrow 120 degrees further around with 415 again between it and arrow prior etc.

If you have what you think, you do have a problem, but it would be a very special motor in any country where 240 volt per phase was the normal supply voltage.

Not sure about that. Years ago (in UK at least) motors were nearly always 415V delta. Full nameplate data should say 415V Δ, 720V Y. Now more likely 400V Δ, 690V Y, but principle is the same.

Nowadays motors wound 400V Y are quite common, so obviously you connect them in star. Delta connection needs 230V. As you say, 230-240V phase-phase supply is not normally available, so in practice unlikely to use delta connection, but it could be done.

Cheers......Codey

I think you have bought the rejected motor from Garage Sale. Three phases can not give different readings.Better go and return the motor to owner or just dump it and buy new one after checking Horse Power, voltage, current and Frequency. For your country voltage should be 415 v and frequency 50 cycles. Horse Power and Amps will depend on your equipment's requirement.

Suresh.Sharma.

There are a few things that you could do, but they come at a cost!

First you could fit a VSD Drive 3ph 400 in 3ph 240 out (done by programming the VSD) make sure that the VS Drive you by has this facility, not all do.

The other option that you could use is, use 3 x (S)400 volt to (L)240 volt line transformers, connect the 400 v across phases (S) and motor to(L).

I have seen this done in the opposite way 240v single phase supply through a single phase VSD to 3 phase, but the output was only 240v 3 ph, so to up the voltage they installed 3 line transformers to up the voltage to 415v 3 ph, this was an interesting concept i had neve seen it done before. The funny part about this was when i got involved i had to replace the VSD i put a 240V single phase to 3 phase unit in removed the transformers and changed the links on the motor from star to a delta connection, reduced the size of the enclosure, but most inportantly the weight.

You could also ask a motor rewinder to change the winding terminals from star to delta, this would depend on the kW Ratting of the motor, most smaller motors when they only have 3 terminals have a star wired configuration connected internaly, but not all.

Also this phase to phase voltage (line to line voltage) causes some concern, they should be equal. There is a fault within the control circuit suppling this motor, is it supplied via a VS Drive or direct on line? If is is DOL check the contactor and overload and supply, you may have a loose connection. Check all anyway.

I have not had time to read all replys to your enqury at this stage, application also may be a factor, is the motor correctly sized?

May the force be with you.

Thanks very much for that. Is there a transformer thingy (Technical level I'm at), that I can buy, that can transform 415v to 240v. Or is there one that would convert 240v single phase to 3 phase.

I think I've seen something like that that workmen carry around with them for big hand held machine tools.

I 've not looked too closely. I think I'll try a google on it.

Thanks

Yes u can buy a transformer or get one custom built.Cost of it however may be equal or > than the motor cost.

What size is the motor I have the transformers from that VSD i replaced the should be ok to about 1.1kW, you can come and pick them up for a couple of boxes of beer.

In japan they have 3 ph 200V, 220V etc.This motor cannot be used on 415 volts.best is write to Panasonic explaining the situation.they may wither give a solution or replace it.

I don't mean to state the obvious, but are you sure you have 3 phase power? If this is a residence it is unlikely that you have 3 phase power. Like on a clothes dryer or a stove there are 3 wires (and sometimes a 4th ground or earth). In the US these are wired such that from prong 1 to 2 it's 115V. From 2 to 3 its 115V from 1 to 3 its 230V. The voltage may vary depending on how far away you are from a transformer and other things. The voltages you are state indicate that you are across the big pond in Europe.

If it's a standard motor it is possible to rewire the motor. Some motors are built to have the voltage switched. Typically this changes the torque curve and the speed, so you have to understand how this will work for what you are doing. Have you checked with panasonic?

My suggestion is to take the dang thing back and call an electrician. Tell the boss or wife (same thing) you messed up. It's not a matter of life and death.

Have a good day :-)

I tried to do a phasor diagram of your voltages (420, 185, 240 L-L and 240,240,78 L-E)

Based on this it is almost sure that you are not 3 phase suppled. By some way, your supply is from a 420V transformer with center tapping.

And that too with the center neutral floating at approx 78V

had you had a normal 3 phase power supply, it was easy for you to step down through a transformer to the required voltage and may be this ratio transformer is available off the shelf (though not very sure) and assuming the KVA (or to be simplistic power ) rating is not too high, the cost will not bemuch.

But that all is provided you have/want to use the motor for some reason.

Else get hold of a proper motor (and get your supply rectified first). It is quite lucky that you don't have 3 phase appliances.

Still I don't understand how other appliances are working/ connected?

Maybe you can purchase a variable speed drive. Input 240V single phase and get 240V 4 phase. With that, you can hook up this motor.

If you are in a workplace and bought it through your company account, you should be able to return it and get the right one, so long as you have the paperwork and haven't damaged it.

try a step down transformer between the power source and the motor

Can you return it and buy the right one?

Hi, this motor is only 0.75kW, so the answer is simple, purchas a Variable Speed Drive that has a single phase input supply of 230v and then you will get a 3 phase output of 230v 3 phase, the great thing about this is that you can sell the idea to the customer that they will then have the ability to alter the speed if necessary.

The other thing that you can look at is, does the motor terminal box have 6 motor terminals? If it does you could probally change the wiring from delta wiring to star wiring.

Best Reagards

Joe

May the force be with you

PS Hi John DG, I am back!

Cheers