re-coil a electric motor 1

[Havana Cuba]

Dear members,

I'm new here but my native lenguage is NOT English so sorry in advance for some writing errors.
I'm living also in Havana, Cuba where I'm now (please don't get jealous) you can buy any food you like over there, I'm dying for a good, large hamburger.

I need to re-coil a electric motor because of burning trough.
Sended the pump to a electrical mechanic to do the job.
Got back the pump and during the testing got a result of approx. max. 30% of it's original pressure and aprox. 1600 RPM"s.
He admitted that he didn't counted the original windings during demolision.
He copied a sort of similar electric motor.
After a few ugly words he refused to do the job again and got back the payment.
So before I go to another electric mechanical Ihave some questions.

First the specs. acc. the tag plate:

115 V, 4,2 A, 60 Hz
0,5 HP, 0,47 kW
3400 RPM
max. press. 3,2 bar


My findings:

Motor is 1-fase
Should be coiled 2 poles
Stator has 24 slots
With coil 1,575"
Intern stator radius 1"

Accoording a formulas found on the net the amount of windings should be 365.
Got a result of 3450 RPM's (matches approx. the tag plate)
And all that thanks to the internet.

Question:
Is the number of windings inclusif the SECUNDAIRY winding?

Now has the stator 8 slots filled with a thinner wire (the starting coil) located at clockwise 3 o'clock and 9 o' clock.
The other 16 slots is winded with appro. 240 in total (variing from 29 to 31 windings per bundle)


Hope you members can help me.


With kind regard,

S.J. Zonneveld
(Havana Cuba)

 

[waross]

Welcome to Eng-Tips

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Havana Cuba]

Can some one tell me how to rewind that particular motor? Or is this forum just to waist time?
Thank you for 'welcom to the forum"
Still thinking this forum has serious members with knowledge to help others. . . with less knowledge, like myself.

with kind regards

 

[waross]

It has been just over 2 1/2 hours since your original posting.
If you cab find a voluntary forum with faster response times by all means go there.
By the way, some our winding gurus work in India. You may have to wait for leisure times in India for an answer.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Gr8blu]

The first repair shop that got their hands on the machine destroyed the evidence. Unless you can find someone who has taken the data ON THE SAME UNIT (HP, RPM, V, and manufacturer), chances are good you're out of luck in finding an exact match to the original winding.

What you CAN do is estimate the cross-section of a turn (based on voltage, current, and insulation class), work backwards from some other geometry stuff (like the slot geometry) and figure out how much you can put in. Then divide that up to obtain a part-winding start configuration. Will it be enough to get "close" to the original performance? Maybe.

Can someone here tell you what specific winding(s) to put in the machine? Probably not.

Converting energy to motion for more than half a century

 

[wayne440]

@waross- well put.

 

[che12345]

@ Havana Cuba
Please furnish some additional details.
1. The motor is 1-phase. Single phase 115V 60Hz AC motor has two windings viz. main winding and the starting winding respectively. The starting winding is usually a) connected in series with a capacitor permanently or b) connected for a short time during starting; which is controlled by the centrifugal switch or current relay etc. There are other designs on the market.
2. If you can furnish a simple sketch the exact motor windings and how the capacitor is connected/switched could be useful.
Che Kuan Yau (Singapore)

 

[Havana Cuba]

Dear all,

My main question id not answered.
Accooeding a formula found on the net concludes that the amount of windings is 365.

Question: is that number 365 INCLUSIF the start windings?

 

[Havana Cuba]

The formula i've found is:

5 x PI / (width x innerradius) x PI = windings per Volt

so in my case:
Width stator 1,575"
Inner radius stator 1"
Motor Voltage 115 V

15,7 / (1,575" x 1") x 3,14 = windings per Volt

15,7 / 4,95 = 3,17 windings per Volt

motor runs at 115V, that results in 365 windings.



Is this result INCLUSIF the STARTING windings ????

 

[crshears]

Hey Havana Cuba,

Welcome to the forums!

I cannot help you with the formula stuff, but given the small size, low power and low voltage of the motor, is it possible to just get another one? I would have thought that such would be reasonably available . . .

My understanding is that Canada does regular business with Cuba, and some of Canada's doors open directly to the US. It might take you some time, but it might be simpler to just get a new motor than trying to reverse engineer the correct winding configuration since, as Gr8blu so aptly put it, "The first repair shop that got their hands on the machine destroyed [all] the evidence."

Hope this helps.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[Havana Cuba]

Thank you for your advice but here in Havana, Cuba are no stores like in Europe where you can buy anything you like.
Import one from abroad is very risky and painstaking slow.
The postal service here STEALS like hell and if not, the delivery takes months.

So if anyone can answer my (simple) question I will be helped beyond believe.

 

[waross]

The postal service here STEALS like hell and if not, the delivery takes months.

When I was in Central America a good friend would receive "care" packages from her mother in the US.
Little stuff like toiletries shampoo, toothpaste, combs etc.
Her packages were always looted by the postal workers.
She complained to the postal department.
The next shipment had a note inside;
"Thank you for sharing with your friends at the post office."
UPS and Fedex agents would hold shipments for ransom.
I know that first hand.
I hope that one of our winding gurus may be able to suggest how to scale your present winding data to improve performance.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[edison123]

Buy a new motor.

Muthu

http://www.edison.co.in

 

[Havana Cuba]

Thanks EDISON123,

So stupid of mine, it slipts my mind completely.

 

[edison123]

Well, you get what you pay for.

Muthu

http://www.edison.co.in

 

[waross]

Buy a new motor.

Thank you for your advice but here in Havana, Cuba are no stores like in Europe where you can buy anything you like.
Import one from abroad is very risky and painstaking slow.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[crshears]

Moderators: feel free to delete this if I am out of line.

Posters:

Not sure it's my place to say, but please read what's already there before responding with duplicate or other suggestions.

Note: I'm holding up a mirror while typing this, as I myself have missed stuff in a thread before weighing in.

Let's keep it civil, please.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[FacEngrPE]

According a formulas found on the net the amount of windings should be 365.
Got a result of 3450 RPM's (matches approx. the tag plate)
And all that thanks to the internet.

Question:
Is the number of windings including the SECONDARY winding?

I am not a motor winder, so take these comments with some skepticism. I do understand a bit of the isolated history of Cuba which makes rewinding this motor beneficial, while almost all of us would find this rewind not a good economic choice.
Looking at your formula, I am going to Vote as the start and run windings are electrically 90 degrees apart, and are not in series, so they need to be calculated separately.
Your calculation is for the run winding. For the start winding, current (and voltage) will be limited to a lower value by the starting capacitor.

 

[Havana Cuba]

Don't bothter.
I will not waistimg time anymore in this forum. To me it is more like a tea party.

 

[waross]

A 3400 RPM motor running at 1600 RPM?
It sounds as if it was rewound as a four pole motor instead of a two pole motor.
It should be rewound with a two pole configuration.
Then the starting winding placed at 90 degrees to the main winding.
Try this;
Two pole winding.
or this:
Two pole winding.
If your winding looks like this, without the starting winding, it is a four pole motor and will run at 1/2 the speed of a similar two pole motor.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!