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?

 

[TugboatEng]

It's a 2 horsepower motor.

OP needs to take a few steps back. A 2 hp TEFC 3 phase motor is less than $1000 USD and will be much more reliable. If the system can handle the extra speed, fine. If not install a VFD. 2 horsepower VFDs are cheap. If the current system has a single phase contactor the 2 hp VFD will allow this to work without modification to the system. At this point in time VFDs and contactors cost the same (I buy NEMA contactors as I have found IEC contactors unreliable with low quality marine grade power).

 

[edison123]

I am with tugboat. 3-ph, 4 pole, 60 Hz off-the shelf motor matching the driven load is the simplest eliminating the centrifugal switch, capacitors etc. which are additional failure points.

High time OP responded. Otherwise, we are wasting our time.

Muthu

http://www.edison.co.in

 

[waross]

I have found IEC contactors unreliable with low quality marine grade power).

It may not be the power that is crappy.
We had a customer with an outside bridge crane with IEC contactors controlling wound rotor motors.
The power quality was excellent.
Almost every foggy morning one of the IEC contactors would flash over phase to phase and our service man would be out replacing fuses.
We replaced all of the IEC contactors with NEMA contactors and never had another problem.

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

 

[nsalhieh]

thank you all again for participating,
As I have 10 cases, we have sent 2 motors to different workshops for rewinding and ordered another new one 220v 60hz and we will compare results.

 

[waross]

Well you have chosen the most expensive option.
There has been quite a bit of misinformation here from persons who may know a lot about electricity but have never done a frequency conversion.
As someone who has years of hands on experience I am appalled by some of the misinformation that has been posted here.
Your voltage is too low for 60 Hz operation.
You tell us that your motor works but is overheating.
Overheating is a symptom of low voltage.
When I was in a position to deal with burned out motors, the rule of thumb was that it was cheaper to replace motors less than 10 HP than to rewind them.
An exception was motors with special shafts or mounting arrangements.

I suggest that you try running one motor on a voltage close to 264 Volts and check both the results and the cost.
Alternately, if 460V/60Hz (or 230V/60Hz)
I have done a lot of successful frequency and voltage conversions over the years and have never even had to considere a rewind.


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

 

[TugboatEng]

For comparison, a 3 phase 2 horsepower electric motor costs $300-800 USD. A rewind starts at $2500 USD. Maybe you have inexpensive labor available?

 

[crshears]

At least the OP is doing three different trials to see how best to proceed with the remaining seven; who knows, if two of the three tests don't give satisfactory results two of them might get be redone as well.

Something tells me price will be the deciding factor, with performance fighting to even get a seat at the table.

CR

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

 

[waross]

For comparison, a 3 phase 2 horsepower electric motor costs $300-800 USD

I agree with you Tug, but with two comments;
1. A 2 HP positive displacement pump may have a special shaft or mounting. That will push up the cost of a replacement.
2. Don't forget the cost of the 3 phase starter.
And a rewind will change the optimum voltage to be more in line with the proper Volts-per-Hertz ratio.
It's generally easier and cheaper to change the voltage. (Done it many times)

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

 

[che12345]

nsalhieh (Industrial)(OP)22 Nov 23 07:59
"...As I have 10 cases, we have sent 2 motors to different workshops for rewinding and ordered another new one 220v 60hz and we will compare results."
I have the following opinion for your consideration.
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. When you rewind or order a new motor, it should be rated for the (new kW rating at 1662rpm 60Hz), as advised by the pump OEM.
2. Fine you are trying out difference solutions.
3. I strongly recommend consider try out a 3-phase new kW based on the Pump OEM advice, with the voltage and frequency based on the system on board. Note: a) A 3-phase motor eliminates the starting capacitor, centrifugal switch totally. b) with new kW (>1.85kW per pump OEM advice) and voltage rated based on the system voltage on board. NO transformer/auto-transformer is required.
Che Kuan Yau (Singapore)

 

[edison123]

Bill


Not necessarily. If 220 V/60 Hz got the motor up to speed, then any higher V/Hz will only increase the current with a poorer PF. (More magnetization current than real KW work current).

If 220 V/60 Hz did not get it up to speed, then a higher V/Hz would have helped reduce the current but it still could be more than the motor could handle depending on the pump demand.

If OP had a variable auto transformer, he could have tested the motor from 220 V to 264 V, 60 Hz and found the sweet spot of the lowest current and seen if the motor is still getting overheated before sending it for a rewind.

If the pump KW demand at 60 Hz is more than the motor could handle, rewinding it isn't gonna help.

Muthu

http://www.edison.co.in

 

[waross]

I don't need a primer on motors.
Read the posts.
They applied 220V/60 Hz to a motor rated 220V/50 Hz and it is overheating.
Judging from some of the misinformation posted here, (yourself possibly excepted) I may be one of the few here who has successfully done both frequency conversions and voltage conversions.
There are two simple steps:
1. Apply the correct voltage for the new frequency.
2. Use one of several methods to reduce the load if the higher speed causes overloading.
And a special case for capacitor run motors; Adjust the run capacitor rating. (I will defer to your advice as to the proper run capacitor for 60 Hz.)
Only if this is not successful will other conversion methods be considered.
By the way, I have never had to consider other methods.
I have a serious question for you. Could too much run capacitor capacity be increasing the voltage across the winding and pushing it into saturation? (That is when the run capacitor is used in series to shift the phase angle of the start winding and not for PF correction)


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

 

[zlatkodo]

Before redesigning the motor itself, I would test what happens if the motor is connected via an auto-transformer at 264 V.
It is possible that you may need to experiment with the values of capacitors. Also, the centrifugal switch (if it exists) could still cause problems by disconnecting the starting capacitor before the motor reaches sufficient momentum. BTW, is really starting capacitor 40µF?
If there is a possibility in site, the best option would be to redesign the motor from single-phase to three-phase.
Single-phase motors are a 'necessary evil' and should be avoided whenever possible.
ACW

 

[waross]

Before redesigning the motor itself, I would test what happens if the motor is connected via an auto-transformer at 264 V.

Thank you for the support.

actually, we run it as its and we got over heat and......

The starting switch seems to be working.
--------------------
Ohm's law
Not just a good idea;
It's the LAW!