Two speed motor connections 8

[Wba1]

Hi All - we have two cooling tower motors that have both burnt out in the last 12 months- we send them usually to be rewound and come back connect back up with no problems- the contract changed and the motors were replaced by two speed abb motors and old motors not rewound - we only use two Contactors for high and low speed - the motors were connected and both burnt out -
It’s a 6 point connection remotely to a control panel with two contactors - wondering if the motors are correct to use ?
1 - high speed

High speed is star on 1u 1v 1w with connection to winding 2u 2v 2w

2- low speed is connection to 1u 1v 1w - is the other windings not connected as drawing does not state it’s star ? - or is it star - we only have two contactors and when I search two speed motors there are 3 any ideas please

 

[edison123]

High speed is two star (see all 3 phase ends are connected at the star point internally and then shorted again externally at 1U 1V 1W)

Low speed is single star with internal star point only.

The nameplate connections are correct and is called as Dahlander winding producing 1:2 speed ratio.

Frequent motors burn out is most likely because they are under powered for your application.

Muthu

http://www.edison.co.in

 

[waross]

Another name for the Dahlander connection is the consequent pole connection.
Can you post a picture of the nameplate of an original motor and of the nameplate of a replacement motor?
Have you considered going one HP size larger on replacements to avoid burnouts?

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

 

[zlatkodo]

"we only use [highlight red]two[/highlight] Contactors for high and low speed "

Attach external wiring diagram.
ACW

 

[Wba1]

Thank you for your prompt responses- I will be back at work tomorrow morning I will post picture of original motor plate and also the electrical drawings for the existing control drawing to cross ref - really appreciate the assistance- will pop back on in morning with info

 

[petronila]

Hi Wba1,
Motor are connected in a Dahlander variable torque connection. Usually, for this connection, the 2 speed power output ratio is 1/4 that is, High speed power rating is 4 times the lower speed power rating. See attached file.

Best Regards

Petronila

 

[waross]

A Dahlander or consequent pole motor may be wound as a delta or as a star motor.
Delta wound Dahlanders may be controlled with two contactors.
Wye wound Dahlanders require three contactors.
To a purchasing agent tasked with purchasing a consequent pole motor, the difference between wye and delta may be of little consequence.

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

 

[edison123]

Bill - Delta wound Dahlanders? Never seen them.

OP - May be the original motors were two windings, two speeds, hence only two contactors?

The winding you have shown here is one winding, two speeds and it would need 3 contactors.



Muthu

http://www.edison.co.in

 

[waross]

OP - May be the original motors were two windings, two speeds, hence only two contactors?

You may very well be correct.

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

 

[zlatkodo]

Delta wound Dahlanders? Never seen them

.
Look at this.
[URL unfurl="true"]https://winding.wixsite.com/design/post/check-something-new[/url]
Although I'm not sure if it can be called a Dahlander winding. Only two contactors are needed.

Wye wound Dahlanders require three contactors.

Both standard Dahlander variants require 3 contactors unless one of them has 3 changeover contacts, which could be very tricky. In fact, to be 100 % correct all three standard Dahlander variants.

Another name for the Dahlander connection is the consequent pole connection.

There are single-speed motors whose connection is called a consequent pole connection. Therefore, that term does not exclusively refer to Dahlander windings.

Winding Design and Motor Repair

 

[Wba1]

Hi All - the original motor was not returned by the company who replaced the motors that were installed and burnt out in high speed after a few hours- Below is the original drawing of control circuits and the new motor plate - talking with the person who has connected the new motor which is running hot - we are not sure if this new motor is correct as reading above we would need to run 3 Contactors due to it being one winding two speed with 3 contactors
We have put clamp meter and motors pulling 12.5 Amps at high speed was feedback off electrician

 

[edison123]

Wba - Yup, the old motors were two winding two speed and hence only two contactors.

Don't know how your electrician connected the new ABB one winding two speed motors with only two contactors, unless he was manually fixing and removing the 1U1V1W short for each speed.

And yes, your motor is definitely under powered if your current is correctly measured as 12.5 A. You need to go in for 7.5 KW motors to handle 12.5 Amps (if that is the true value measured) with a safety cushion. For the same centrifugal fan, power (or amps drawn) is proportional to the cube of the fan rotational speed.

Best to go back to the original two winding two speed but with higher KW rating that meets your load currents at both speeds. May be a bit more expensive but less complications.

Bill - That's delta/wye Dahlander that would still need 3 contactors for remote control.

As zlatkodo says, while all Dahlanders are consequent pole windings, all consequent pole windings are not Dahlanders.

zlatkodo - Not seeing the connection for delta/delta Dahlander from your photos of wound motors. Is there a connection diagram?


Muthu

http://www.edison.co.in

 

[zlatkodo]

Is there a connection diagram?

Yes, but it is here and it is not free to download.
ACW

 

[zlatkodo]

the new motor which is running hot

Your electrician probably connected the new motor (pictured on the right) with only 2 contactors.
The motor will operate normally at low speed under these circumstances. However, at high speed, it will rotate but will be heavily overloaded and hot because it lacks an external wye connection and motor works with half of winding.
ACW

 

[edison123]

zlatkodo - Nah, I am good.

Let me guess, consequent poles for slow speed and one half of the winding reversed with the same delta points for high speed and hence constant HP at both speeds?

Muthu

http://www.edison.co.in

 

[che12345]

Mr. Wba1 (Electrical)(OP)23 May 23 16:01
"....#1.- we have two cooling tower motors that have both burnt out in the last 12 months- we send them usually to be rewound and come back connect back up with no problems-.....#2. the contract changed and the motors were replaced by two speed abb motors and old motors not rewound - we only use two Contactors for high and low speed - the motors were connected and both burnt out. It’s a 6 point connection remotely to a control panel with two contactors - wondering if the motors are correct to use ?"
I am of the opinion that :
1. the original drawing showing Lo-speed 1.1kW Hi-speed 5.5kW with ONE contactor of Lo-speed and another ONE contactor for Hi-speed is an error? One contactor for Lo-speed and another contactor for Hi-speed is only suitable for TWO separate windings two-speed motor. Unless special request, a P:5P (W) , N:2N (rpm) motors usually for FAN load are manufactured in DAHLANDER YY/Y connection; which required THREE contactors and TWO overloads.
2. The new motor is a standard IEC motor with Dahlander YY/Y winding.
3. Revise your control circuitry to THREE contactors with TWO overloads according to the Dahlander motor wiring diagram.
Che Kuan Yau (Singapore)

 

[zlatkodo]

If I understood you correctly, that's it.
In fact, it's more like a PPM (Pole Phase Modulation) winding rather than Dahlander.

If you decide to repair the ABB motor (Y/YY), you may consider making a small change in the winding data to increase high-speed power and decrease low-speed power, thus aligning the motor parameters with the previous ones.
Let your rewind shop contact us freely.

 

[waross]

You're caught between a rock and a hard place.
Or
Between production and accounting.
You may go for a more powerful motor and accounting will not be happy with the cost.
Or
You may change one of the pulleys (if it is a belt drive) and slow the fan down slightly.
Production may not be happy with the reduced cooling.
Or
Continue burning undersized motors and nobody's happy.

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

 

[edison123]

zlatkodo - To put it somewhat simplistically, in Bill's delta image above, flip 1U and 2U to get the high speed. Of course, it is still single delta, so the HP remains the same at both speeds and the torque is halved at high speed. Not sure which type of load has that high speed low torque requirement. Whether to call this delta/delta a Dahlander is a bit uncertain.

edit:

oth, it follows other Dahlanders property of consequent pole for low speed and regular pole for high speed, so why not?

Muthu

http://www.edison.co.in

 

[waross]

Thanks for the support Muthu.
Looking closer at the diagram, I wrongly assumed that the delta mid-points were simply shorted together.
That would reverse the current flow through all of the windings as compared to the accepted connection.
Would that work but with the unintended consequence of reversing the motor?
I actually had an application where that may have been an advantage.
A large motor was feeding boards into a planer.
When the boards jammed, the feed kept running but slipping.
The heat caused by the friction would soon cause the moisture in the board to flash into steam and the board would explode.
Then the planer would have to be dismantled in order to be cleaned.
This would be avoided by plugging the motor into reverse to back the board out before it exploded.
Backing out at a lower speed would have been a lot easier on the motor.
But that was a long time ago and I'm not going back there.

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