Thread: DELTA mode wiring

Originally Posted by RayG

Hi Mike,

Yes, I see what's happened.... Graziano has sussed it nicely.

Regards
Ray

It was my fault Ray. As Graz pointed out, my circuit drawing wasn't correct in the first place . I have a great ability to confuse people Mike

Hi Mike,

Well, it's not really your fault, taking it to the motor rewinder place was the right thing to do. I would have expected the motor repair place to have done their job a bit better.

Maybe you have a case for a complaint, if not a refund.. (depends on what they have to say)

Regards
Ray

Originally Posted by RayG

Hi Mike,

The way I drew was for the high voltage 440V and if you followed that and the motor was ok it would have run fine, just not full power however, the diagram shows how to wire it for 220.

Just because a motor tests ok with a multimeter doesn't mean it's good, you need a megger to test properly.

The place you took it to, are they a motor rewinder?

Regards
Ray

and then sometimes when the megger and ohm meters say it should be ok, it may still have a internal wiring/rotor defect which can result in the motor not running correctly and or even to cause to the smoke to be released ...unintentionally of course

Did no-one pick the fact that this is/was a 60 Hz motor? They will not normally have a useful life expectancy on our 50Hz power, as they do not have the extra metal mass in the laminations to operate effectively at 50 Hz without overheating. Rotor to pole clearances are also different, thus it may have already suffered heat damage and been beyond salvage. The only 60 Hz motor I ran at 50 Hz was so hot in 15 mins you could fry eggs on it! Good to know you now have the right motor, regards, Combustor.

Hi Combustor,
Without commenting on the rest of your post. Why would the rotor to pole clearance be different? Wouldnt that be something that was kept "as small as possible"(for a given price)
Stuart

My electrical theory is not extensive, but it is my understanding that AC devices,(motors, transformers etc). can be made with much less pole mass as frequency rises. Believe that much early aviation electrics were 400 Hz, as the components were a whole lot smaller and lighter. Le Tourneau's electric earthmovers were similar. Also told that higher frequency needs greater air gap rotor clearances in motors, alternators etc. Some areas of our state had 40 Hz systems prior to the interconnected grid, and when supply authorities converted customer equipment, most motors had metal machined off the rotor, and a pulley change to correct the output speed. Sure someone with greater knowledge can explain it better for those who are curious. Regards, Combustor.

Originally Posted by Combustor

Did no-one pick the fact that this is/was a 60 Hz motor? .

Does it make any difference that It's running off a vfd?

Generally you might get overheating problems if you run so slow that you don't get any fan cooling. Otherwise it doesn't matter too much.

Regards
Ray

Originally Posted by RayG

Generally you might get overheating problems if you run so slow that you don't get any fan cooling. Otherwise it doesn't matter too much.

I'm with you Ray

going real slow may be a problem but 60 V 50 hz??at high speed..no problem...it would work fine.

Lots of USA equipment comes into Australia rated at 60hz...all one has to do is de-rate it to allow for the slower speeds at 50hz

I just did a test with the old motor wired as per the above diagram e.g., for low voltage .

Interesting . The motor turns over fine to begin with , then, after about 2 seconds , after the VFD has ramped up to around 5 amps output , then the VFD shuts off and it displays PL ... this means a short circuit is happening .

Maybe the old windings are stuffed and are leaking , after reaching 5 amps the insulation breaks down , it cannot handle the current above 5 amps.

This is all a academic exercise . But I do have the thing connected OK now, as at least it is rotating now .

Mike

Good to see you got it to spin, usually if there's a serious short an error will pop up immediately not after it's run for a while. I wonder if there some other problem causing that error, I used to get a fault on my inverter as the braking time was set to an unrealistically short time, once it was changed it ran fine. The windings could have just picked up a bit of moisture from sitting so long unused and require a low temp (50 deg C) baking in the oven for a few hours. A bit of moisture can do funny things.

Originally Posted by Graziano

Good to see you got it to spin, usually if there's a serious short an error will pop up immediately not after it's run for a while. I wonder if there some other problem causing that error, I used to get a fault on my inverter as the braking time was set to an unrealistically short time, once it was changed it ran fine. The windings could have just picked up a bit of moisture from sitting so long unused and require a low temp (50 deg C) baking in the oven for a few hours. A bit of moisture can do funny things.

Yes Graz , it seems odd that it runs OK , then stops . I am going to try the VFD settings . It stops very suddenly , it doesn't ramp down at all , it just goes "STOP" very quickly with no slowing down like a normal motor does , like a brake is applied .

I should have dried out the stator while it was apart, I was going to warm it up , but I forgot Anyway its progressing ..MIKE

Hi Mike,
I've had the odd motor that needed a little drying out. I just have a fan heater blow on them for awhile(though they were open frame motors).
Does it stop at the same point each time?

Stuart

Originally Posted by Stustoys

Hi Mike,
I've had the odd motor that needed a little drying out. I just have a fan heater blow on them for awhile(though they were open frame motors).
Does it stop at the same point each time?

Stuart

Hi Stuart

Ok I've done some more testing .

I've now got the motor running without stopping . But, I had to reduce the VFD output Freq. down to 25 hz to do this . At 25 hz , the motor ran continiously , but the VFD was putting out too many amps , about 8 . As the motor warmed up, I noticed something odd, the amps slowly came down ! The amps crept downwards to 5 amps . The motor was now warm to touch .

I then ran the motor for a few minutes at 25 hz . And, then tried going up to 30 hz .... yes it still ran, but after going up to 35hz ..no good , the VFD shut down again ..too much current . If the current goes over about 12 amps the VFD shuts off .

I think the old windings are so leaky , they are drawing twice the current what they should be . As the motor cools down after being stopped , after then starting it up again , it goes back to drawing higher amps . As it warms up, while it is running , the amps go down ....

Mike

Doesnt sound good, but what would I know. How many Hp is it again? I cant read the plate

Stuart