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

 

[jraef]

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

 

[che12345]

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)

 

[edison123]

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

http://www.edison.co.in

 

[che12345]

@ 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)

 

[Wba1]

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

 

[edison123]

che - oh... ok.

Muthu

http://www.edison.co.in

 

[jraef]

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

 

[edison123]

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

Muthu

http://www.edison.co.in

 

[cliff reed]

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.