Want to rewind motor (single phase 220v 50 hz) into (single phase 220v 60 hz) 12

[nsalhieh]

Hi All,

if you can help us to rewind motor (single phase 220v 50 hz) into (single phase 220v 60 hz)

Motor specification:
- have 2 capacitors (starting 40uF 240V) & (RUNNING 50uF 400V)
- 1.85 Kw
- 1385 rpm
- application for sea water high pressure piston pump

WHAT IS THE EQUATION?

 

[waross]

Step 1: Increase the 60 Hz voltage to 264 Volts, 60 Hz. (note 1)
Step 2: Decrease the run Capacitor to about 40uF to 45uF.
Note 1; In many places, the standard 60 Hz voltage is 240 Volts.

A 240V:24V lighting transformer reconnected as an auto-transformer will deliver 264 Volts.​

In the event that your voltage is 220 Volts;

A 240V:48V lighting transformer connected as an auto-transformer will deliver 264 Volts.​

Note 2; For a 240 Volt supply, the transformer should be about 500 VA or greater.

for a 220 Volt supply, the transformer should be about 750 VA or greater.​

The pump will run faster.
You cannot rewind for the same speed at 60 Hz.
The equations depend on the Volts per Hertz ratio.
For your motor the V/H ratio is 220/50 = 44 V/Hz.
At 60 Hz, 60Hz x 44 = 264 Volts required.
At 60 Hz, 1385 RPM x (60Hz/50Hz) = 1662 RPM

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

 

[LittleInch]

Nsalhiah,

Why bother?

What are you trying to do here?

Pump spins faster means more power needed from the motor.

Rewinding doesn't seem to make much sense compared to buying something designed for the voltage and frequency you have.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[che12345]

nsalhieh (Industrial)(OP)19 Nov 23 13:59
" if you can help us to rewind motor (single phase 220v 50 hz) into (single phase 220v 60 hz)....WHAT IS THE EQUATION?'
1. One of the very important factors is the speed, a pump at 1385rpm @ 50Hz will be running 1662 rpm @ 60Hz. The power (1.85kW @ 50Hz) will be increased to (> 1.85 kW @ 60Hz), with increase in volume. Check with the pump OEM the new kW @ 1662rpm. If 1385rpm output volume is fine, you may have to regulate the valve, as you are unable to control the new speed (@1662rpm).
2. Consider the learned advice by Mr. LittleInch.
Che Kuan Yau (Singapore)

 

[waross]

Pump spins faster means more power needed from the motor.

At the proper voltage on 60 Hz, the motor will develop more power.

Rewinding doesn't seem to make much sense compared to buying something designed for the voltage and frequency you have.

Compare the price of a transformer versus the price of a new motor (and possibly an integral pump.)

If 1385rpm output volume is fine, you may have to regulate the valve, as you are unable to control the new speed (@1662rpm).

Quite possibly, but you should not attempt to throttle the flow of a positive displacement pump.
Net discharge may be controlled by bypassing some of the flow back to the suction side of the pump or back to the sea.
Your regulating valve will be in the bypass line.
Typical costs for voltage change for small motors.
Highest cost: Rewind.
High cost: Replacement motor.
Lowest cost: Auto-transformer.

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

 

[edison123]

You can most likely run it as it is at 60 Hz if it meets the connected load demand at that increased speed.

Muthu

http://www.edison.co.in

 

[che12345]

"...Note 2; For a 240 Volt supply, the transformer should be about 500 VA or greater. for a 220 Volt supply, the transformer should be about 750 VA or greater...."
1. The motor running at 1385rpm (50Hz) is rated 1.85kW. At 1663rpm (60Hz) will be >1.85kW.
2. How can a transformer rated 240V about 500 VA or greater, or 220V about 750VA or greater; which is <1/3 or <1/2 of motor (>1.85kW at 60Hz) be suitable for the job?

Che Kuan Yau (Singapore)

 

[nsalhieh]

thank you all for the answers

actually, we run it as its and we got over heat and the measured temperature at the outside cover of motor reached to 105c within 30 min of running so we stop at the that point. the problem with existing situation is that the motor will get damage and this is why we are thinking to rewind according to supplied power that is now 220v 60hz supplied from auto transformer getting main feed power 450v 60htz out of generator on ship

we need the rewinding equation to make sure rewind the motor again to get red of the over heat problem

Note: our RO system have automatic pressure regulating valve at reject line this is why the system will run at constant desired pressure regardless of rpm.

we need the rewinding equation for the motor at 220v and 60 hz

 

[edison123]

Post your 220 V, 50 Hz and 220 V, 60 Hz load currents first.

Muthu

http://www.edison.co.in

 

[LittleInch]

Well at 20% more power, plus higher amps as the V/htz ratio is lower I'm not surprised.

But first check out what the pump is doing. Flowrate is fixed but what's the pressure compared to the data sheet?

Buy a new motor properly specced for 220V 60Htz

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[waross]

2. How can a transformer rated 240V about 500 VA or greater, or 220V about 750VA or greater; which is <1/3 or <1/2 of motor (>1.85kW at 60Hz) be suitable for the job?

Auto-transformers 101.
With a 120:48 Volt auto-transformer Boosting a 10 Amp motor current, only the 24 Volt winding sees the ten Amp motor current.
10 Amps times 48 Volts = 480 VA.
But the 10 Amps was a guesstimate. At 1385 RPM your slip is 115 RPM.
115 RPM is a relatively high slip and high slip motors tend to have more losses, so a typical current estimate tends to be low.
Thus I opted to recommend transformers a little on the high side.
This formula is for step-up applications only.
For step down applications, the transformer primary current must be added to the secondary current to determine VA rating.
Dropping from 450 Volts to 264 Volts will be extremely difficult to do with standard transformer voltages.
But don't panic; 450 Volts line to line will have a line to neutral voltage of 260 Volts.
Capacitors may be a problem.
If the run capacitor is carrying part of the motor current, it may be causing part of the overheating.
Typically, the run capacitor shifts the phase angle of the current applied to the start winding so that the start winding may assist the main winding by supplying added torque.
With a higher frequency, the capacitive reactance will be lower and this may be causing the start winding to take a disproportionate share of the load.
The solution; A lessor rated run capacitor.

Given the actual motor current, for auto-transformer step up I use the equation:
Motor current x Transformer secondary voltage = VA transformer capacity.
10 Amps x 48 Volts boost = 480 VA.
Note: If 10 Amps is the actual motor current, I would use a 500 VA transformer.
Given that the 10 Amps is a guesstimate, I recommended the next larger size transformer eg: 750 VA.
By the way, over the years I have several times done successful 50/60 Hz and 60/50 Hz conversions.
I have converted 50 Hz motors imported into Canada's 60 Hz grid and I have converted 60 Hz motors exported to 50 Hz grids.

Note: our RO system have automatic pressure regulating valve at reject line this is why the system will run at constant desired pressure regardless of rpm.

It may be well to check the actual pressure if this has not already been done.
The increased flow may be too much for the pressure regulator and the actual pressure may be higher than anticipated.

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

 

[petronila]

nsalhieh,

There are some important factor to consider due to incresing the RPM will increase the demanded power from pumps applications up to 1.7 tiems due to affinity laws thus even if you can redesign the winding from 50 Hz to 60 Hz you should trim the pump impeller. However, some of this single-phase motors are equipped with centrifugal switchs if this is the case the change to 60 Hz is not advisable because the centrifugal swith is already setted for the original RPM and is not designed to operate proper at 1.2 the speed thus if the start winding can not disconnec the winding will smoke up.

There are a couple of alternatives here:

1. Verify the application requirements and replace the actual motor with the proper single-motor motor at 60 Hz as Littleinch recommend.
2. Replace the actual motor with a three-phase motor of about 2 times the actual rating, connecting the three phase windng with an steinmetz coinnection;you should calculate a capacitor. See links below

https://ieeexplore.ieee.org/document/63144

https://www.mig-welding.co.uk/forum/threads/steinmetz-connection.132549/

Best Regards

Petronila

 

[jraef]

There is a member here, zlatkodo, who frequently posts or responds to motor winding techniques, hopefully they see this thread. But if not, here is what I think is their website, where they show some links to on-line calculators.

https://winding.wixsite.com/design

Still, I agree that unless this motor / pump is so specialized that the motor cannot be exchanged, you will likely spend a LOT more money trying to rewind it than you would just buying a new motor with the correct voltage configuration.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[waross]

There are some important factor to consider due to incresing the RPM will increase the demanded power from pumps applications up to 1.7 tiems due to affinity laws thus even if you can redesign the winding from 50 Hz to 60 Hz you should trim the pump impeller. However, some of this single-phase motors are equipped with centrifugal switchs if this is the case the change to 60 Hz is not advisable because the centrifugal swith is already setted for the original RPM and is not designed to operate proper at 1.2 the speed thus if the start winding can not disconnec the winding will smoke up.

"There are some important factor to consider due to incresing the RPM will increase the demanded power from pumps applications up to 1.7 tiems due to affinity laws"
The laws that you cite do not apply to a positive displacement pump.
"you should trim the pump impeller" No impellor in a PD pump.
"not advisable because the centrifugal swith is already setted for the original RPM and is not designed to operate proper at 1.2 the speed"
The centrifugal switch will open. The switch does not care what the terminal speed is, It opens when the rotor is turning fast enough for the main winding to generate torque.

It is so much easier to supply the correct voltage than to rewind to accomodate a small change in optimum voltage.
50 Hz motor speeds are based on base speeds of 3000R PM, 1500 RPM, 1000 RPM, 750 RPM.
1385 RPM = base speed 1500 RPM minus 115 RPM slip.
60 Hz motor speeds are based on base speeds of 3600 RPM, 1800 RPM, 1200 RPM, 900 RPM.
REWINDING CANNOT CHANGE THAT.
IF THE FREQUENCY IS INCREASED THE VOLTAGE MUST BE INCREASED IN THE SAME RATIO.
TRY THE CORRECT VOLTAGE FIRST.
The motor is working but is overheating? That is a symptom of low voltage. Try the correct voltage.
The capacitors will draw more current on 60 Hz. You may have to reduce the capacity of the capacitors.

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

 

[LittleInch]

Waross, this is a ship where clearly the supply is 220V 60 htz. I don't think the OP want to add a special tx just for this pump.

He or she clearly just picked up an RO unit from shore and plugged it in not fully realising what would happen going 50 to 60 htz, but the same voltage.

Messing about with convertors or txs etc is just more expense and given the motor is probably cooked by now, just replace it .

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[petronila]

Waross

The problem with the centrifugal switch is real and it is a factor. You can not grant the Centrifugal Switch will works proper for the new speed. Adding a boost transformer is more expensive beceause you will need to size the transformer at leat 3 times the power of the motor and if this is a ship you may not have space for installing new equipment including the controls also the transformer is not standard and needs to be custom made. The user should wait long time instead new motors are easy available.

Just replacing the motor seems is a good option.

Petronila

 

[waross]

Waross, this is a ship where clearly the supply is 220V 60 htz. I don't think the OP want to add a special tx just for this pump.
He or she clearly just picked up an RO unit from shore and plugged it in not fully realising what would happen going 50 to 60 htz, but the same voltage.

Do yourself a favour and read the previous posts.
According to one of the posts that you neglected to read:
" 450v 60htz out of generator on ship"
There is already an auto-transformer transformer installed to supply 220 Volts.
The motor wants 264 Volts according to the Volts-per-Hertz law.
The line to neutral voltage of a 450 Volt generator is 260 Volts.
260 Volts to a 264 Volt motor is well within tolerance.

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

 

[TugboatEng]

The ship's generator at 450 volts is most likely an ungrounded system without a neutral. It's possibly delta wired.

 

[waross]

The problem with the centrifugal switch is real and it is a factor. You can not grant the Centrifugal Switch will works proper for the new speed.

The centrifugal switch typically operates at a few hundred RPM. A 1385 RPM motor, a 1685 RPM motor and a 3500 RPM motor will all turn fast enough to properly operate the centrifugal switch.

Adding a boost transformer is more expensive because you will need to size the transformer at leaat 3 times the power of the motor

Stick to what you know.
The standard industrial voltage in Canada is 600 Volts. We get a lot of 480 Volt equipment from the US.
Some industrial plants opt to install their own transformers and use 480 Volts, but the have to accommodate 600 Volt motors (Actually 575 Volt rated motors are used on 600 Volt systems.
Using auto-transformers to covert between 480 Volts and 600 Volts is a frequent chore in Canada.
The KVA rating of the boost transformers is typically 5/16 of the motor KVA dropping to 480 and 1/4 of the motor KVA boosting to 600 Volts.
For a conventional transformer supplying a motor, a transformer KVA of 125% of the motor KVA is common.
That said, I have seen transformers sized at 300%.
It was in the third world where kickbacks were common.
All of the suppliers offered a nice, under the table, rebate to any electrician bringing in a transformer order.
The worst case that I encountered was a 150 KVA transformer bank to supply a 17 KVA load.
So, yes, in some areas 300% transformer capacity is justified.

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

 

[waross]

The ship's generator at 450 volts is most likely an ungrounded system without a neutral. It's possibly delta wired.

Fair comment, Tug.
I considered that and decided not to mention it unless the OP mentioned it.
An artificial neutral (grounded or floating) is not hard to field fabricate.
Three lighting transformers connected in wye:delta will develop the artificial neutral.
The primary voltage must be above 260 Volts and the secondary (delta) voltage does not matter.
I won't guesstimate sizes until the OP reports the motor current.
In any event less than 1000 KVA.



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