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Two speed motor connections
8

Two speed motor connections

Two speed motor connections

(OP)
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 🙏🏻

RE: Two speed motor connections

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
www.edison.co.in

RE: Two speed motor connections

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!

RE: Two speed motor connections


Quote (Wba1)

"we only use two Contactors for high and low speed "

Attach external wiring diagram.
ACW

RE: Two speed motor connections

(OP)
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 👍🏻

RE: Two speed motor connections

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!

RE: Two speed motor connections

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
www.edison.co.in

RE: Two speed motor connections


Quote:

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!

RE: Two speed motor connections

2

Quote (edison123)

Delta wound Dahlanders? Never seen them
.
Look at this.
https://winding.wixsite.com/design/post/check-something-new
Although I'm not sure if it can be called a Dahlander winding. Only two contactors are needed.

Quote (waross)

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.

Quote (waross)

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

RE: Two speed motor connections

(OP)
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

RE: Two speed motor connections

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
www.edison.co.in

RE: Two speed motor connections

Quote (edison123)

Is there a connection diagram?
Yes, but it is here and it is not free to download.
ACW

RE: Two speed motor connections

Quote (Wba1)

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

RE: Two speed motor connections

zlatkodo - Nah, I am good. smile

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
www.edison.co.in

RE: Two speed motor connections

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)

RE: Two speed motor connections

Quote (edison)

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

Quote (Wba1)

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.

RE: Two speed motor connections

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!

RE: Two speed motor connections

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
www.edison.co.in

RE: Two speed motor connections

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!

RE: Two speed motor connections

Dahlander / 2S 1W motors require a 3 contactor control scheme, 2 contactors was for a 2S2W motor. You needed a different starter arrangement altogether. Or just use a VFD…


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

RE: Two speed motor connections

Mr. Wba1 (Electrical)(OP)23 May 23 16:01
1. The original drawing shows Two contactors. Designed for Lo-1.1kW 4.0A (rpm ?), Hi-5.5kW 10.5A (rpm ?). This is designed for a 2-speed two separate stator windings motors. NOT suitable for any DAHLANDER wound motors, which require THREE contactors.
2. The proposed motor with YY 5.2kW 1445rpm, Y 1.35kW 715 rpm shown on the name=plate is a 4/8 pole with Dahlander connection; which would required THREE contactors.
3. If the Hi and Lo speeds are in order, but 5.2kW is < 5.5kW required, the next higher standard IEC YY/D Dahlander connection motor is Hi-7.5kW Lo-4kW.
Note: a) For Dahlander connection motors, you need THREE contactors.
b) even if you go for this next higher rated motor, the existing two contactors and the two thermal overloads are likely to be within the rating. Therefore no replacement is required.
c) revise the control, add an additional contactor for Dahlander connection motors.
Che Kuan Yau (Singapore)

RE: Two speed motor connections

Jeff's suggestion of a standard VFD duty motor (cheaper than two winding or Dahlander) with VFD gives various speed options instead of only two and gets rid of at least one set of contactors. Both the motor and VFD are dime a dozen.

And you need to still uprate your motor capacity to suit your load current at the highest speed.

Muthu
www.edison.co.in

RE: Two speed motor connections

2
@ Mr. edison123 (Electrical)25 May 23 02:37
"....Jeff's suggestion of a standard VFD duty motor (cheaper than two winding or Dahlander) with VFD gives various speed options instead of only two and gets rid of at least one set of contactors...."
I do not have any price comparison data between a 2-speed two windings/Dahlander motor to that of a FVD certified motor. The following issues would favour a standard 2-speed motor.
a) what is needed is 2-speed. There is NO requirement for Variable speed.
b) a VFD unit, with large number of big capacitors are sure to fail/age within say five years. It is likely that in-house technicians are unable to trouble-shoot it at all, not to mention repairing it, impossible!
Consider also the possible bearing circuiting damaging current and replacing the existing cables with Special screened cables from the VFD to motor, would cost a bomb!
c) need to find a space to house the VFD and seriously investigate whether the existing cubicle IP is able to fulfil the additional cooling air requirement.
d) the cost of a VFD would be >>>> more than by adding ONE contactor.
Che Kuan Yau (Singapore)

RE: Two speed motor connections

(OP)
Hi All,

I really do appreciate everyone who has replied on this thread it’s been invaluable and really appreciated by myself and the Electrician working with the issue. As it stands the two new motors which have been delivered are not going to be installed as the information that’s been provided by yourselves they are obviously not correct to the two Contactor set up.

The drawing which shows control circuits with two contactors has been sent to the sales team who provided these motors off the drawing you all have said relates to a two winding - two speed motor - I have asked for feedback on why they sent a motor that was not correct to information provided so that we can start dialogue on a means to a solution- in the mean time I have an inverter that we are considering setting up for one cooling tower but need permission to use it as it’s a spare for an extract AHU and we will need to run BMS cables etc so not a quick fix - I will continue to read your comments and update the next stage/ outcome from feedback etc but not too confident on getting motors exchanged- wish me luck and I will provide update when necessary- Thank you all again 👍🏻

RE: Two speed motor connections

Quote (Wba1)

I have asked for feedback on why they sent a motor that was not correct to information provided so that we can start dialogue on a means to a solution-

My prediction: they will come back and say something along the lines of “All you said was that you wanted a 2 speed motor, nobody said it needed to be 2S2W…”. I’ve been down a similar road a couple of times and in one case, the mistake was made at the purchasing level in that they came back and said “Nobody told us there were different types of 2 speed motors…”.

I do not agree with Che’s assessment of using an inverter drive. You can use it on the existing 2S1W motors if necessary, so long as you take the proper precautions if the motor is not “inverter rated”. And if every drive failed after 5 years, the entire inverter drive industry would collapse in 6…. That simply is not true. I routinely have to convince users to replace 30 year old drives simply because parts are scarce for “old tech” (especially after COVID) and the newer technology offers them much better integration options now, not because they are failing.


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

RE: Two speed motor connections

Jeff - bearing circuiting damaging current, cost a bomb... yeah, lot of bad takes in that post.

Muthu
www.edison.co.in

RE: Two speed motor connections

Resolution:
Multispeed motors are available in two basic versions:
1) separate winding and 2) consequent pole.
A separate winding motor has a winding for each speed while a consequent pole motor has a winding for every two speeds (three-speed motors have two windings).
The motor connections (and thus the types of controllers) for two speed starters are exemplified by the schematic diagrams shown in Table 16.22. Note that consequent pole two-speed controllers involve a 5-pole and a 3-pole starter, while separate winding controllers have two 3-pole starters.
Verify the type of motor before ordering. Field modification of starters to match the motor may not be possible.
Separate winding motors are usually chosen when flexibility is important, since the speeds of a consequent pole motor are usually limited to a 2/1 ratio; a broad range of speeds can be obtained on a separate winding motor.
Both separate winding and consequent pole motors are available in three types:
1) constant horsepower, 2) constant torque, and 3) variable torque.

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