wound rotor 8/4 poles

[bum2]

Hello. We have a Chinese-made motor with a wound rotor YZRDW250M-8/4 30 kW under repair. The rotor was rewound, the stator has a factory winding. Please help connect the rotor winding. As I understand it, the rotor winding is 8 poles, when operating at 750 rpm, the rings close, and when operating at 1500 rpm, the rings open. At 750 rpm (with closed rings), it works fine for us, but at 1500 rpm (with open rings), there is no rotation, the rotor can be turned by hand at the rated voltage on the stator. Thank you very much in advance for your answers

 

[jraef]

Rings opening and closing is not a WRIM... If the ring circuit opens, the motor wouldn't work. Or are you talking about SHORTING the rings?

Are you sure this isn't a Repulsion / Induction motor? That's a really old, kind of forgotten technology though, I don't know why anyone would resurrect it...

 

[waross]

Good call on the induction repulsion motor, Jeff.
There should be a shorting bracelet that shorts the commutator when the brushes are lifted.
If the bracelet is not moving into the proper position the motor will stall.
Or;
A two speed WRIM?
Possible I guess.
The two speeds will be wound on the stator.
The rotor will need either a short or resistors on the slip rings at either speed.

 

[zlatkodo]

Hi, Bum,
I presume it's a crane motor.
Yes, it's a two-speed wound-rotor induction motor. Regarding the rotor winding design itself, we know several (at least 10) different versions so far, from very simple to very complex ones. Keep in mind that there are no standards for the construction of these motors, but they are custom-made, even though they are produced in large series.
The rotor usually has 48 slots, less often 72. Stator has 60 slots usually.
If you provide us with all the data you have and any winding diagram you have made (even incorrect), we might be able to help you solve the problem.
ACW

 

[waross]

but at 1500 rpm (with open rings), there is no rotation

That is to be expected with an open rotor circuit.

 

[bum2]

Hi, Bum,
I presume it's a crane motor.
Yes, it's a two-speed wound-rotor induction motor. Regarding the rotor winding design itself, we know several (at least 10) different versions so far, from very simple to very complex ones. Keep in mind that there are no standards for the construction of these motors, but they are custom-made, even though they are produced in large series.
The rotor usually has 48 slots, less often 72. Stator has 60 slots usually.
If you provide us with all the data you have and any winding diagram you have made (even incorrect), we might be able to help you solve the problem.
ACW

Hello. Thanks for your quick reply. I am sending you the winding data. The number of turns is 11, the pitch of the slots is 1-6, the diameter of the conductor is 1.4x4 (approximately 6.1 square millimeters). The length of the rotor active steel is 350 mm, the diameter is 280. This data was taken from the factory winding, the connection diagram is lost...

 

[jraef]

Ah, duh, two speed motor! Missed that possibility…

But although I can see them having a mechanism for disconnecting the resistors for the rotor brushes DURING the transition from one speed to the next to avoid a transition spike, it would have to reconnect them again once that’s done. So it sounds as though something is broken in that system.

I don’t see the value in actually lifting the brushes though, if that’s what you meant. That seems overly complicated and I don’t think it would be necessary, because just opening the circuit to the resistors with a contactor would accomplish the exact same thing.

 

[waross]

When you stop trying to run the motor with an open rotor circuit, you may find that there is nothing wrong with the motor.
FIX THE OBVIOUS FIRST.

 

[edison123]

Do you have six sliprings?

 

[waross]

I don’t see the value in actually lifting the brushes though, if that’s what you meant.

My comment about lifting brushes was in regards to the possibility that this was a repulsion-induction motor.

 

[bum2]

У вас шесть токосъемников?

3

 

[bum2]

all that is known about the factory rotor circuit is a single-layer winding, pitch 1-6, 48 slots, 2 stars constantly on.
in the attachment it would seem that the circuit is correct, but it only works when the rings are closed (8 poles), when opened, the shaft rotates by hand at the rated voltage on the stator

 

[zlatkodo]

Hi, Boom2,

Boom2: "the connection diagram is lost..."

I'm surprised that after performing a new rotor winding, you are unable to describe its configuration.
Please draw a diagram illustrating how you performed the winding, because as you reported, the motor operates at one speed but not at the other.
By the way, the type YZRDW250M-8/4 motor means nothing. The days when the type of motor could tell you what is inside and what kind of winding it had are long gone. Unfortunately
ACW-Contact

 

[waross]

but it only works when the rings are closed (8 poles), when opened, the shaft rotates by hand at the rated voltage on the stator

Induction motor theory 101.
Current in the stator winding causes a magnetic field.
That magnetic field induces a current in the rotor winding (Or squirrel cage winding)
The current in the rotor winding causes a magnetic field.
the interaction between the stator magnetic field and the rotor magnetic field develops torque.
This only works when the rings are closed (8 poles),
The slip rings add resistance to the rotor circuit.
They do not change the number of poles.
A WRIM is never meant to operate with an open rotor circuit.

"only works when the rings are closed (8 poles), when opened" there is no rotor current, no rotor magnetic field and no torque.

 

[edison123]

all that is known about the factory rotor circuit is a single-layer winding, pitch 1-6, 48 slots, 2 stars constantly on.
in the attachment it would seem that the circuit is correct, but it only works when the rings are closed (8 poles), when opened, the shaft rotates by hand at the rated voltage on the stator

This will work only if there is a second slipring unit at the bottom instead of a short.

 

[waross]

Consider a squirrel cage.
The rotor pole count does not have to match the stator pole count.
Changing the resistance in the rotor circuit changes the speed:torque characteristics of the motor.
Open slip rings represents infinite resistance in the rotor circuit and the torque goes off scale, on the zero end of the scale.
Your motor is doing what it is expected to do.

 

[zlatkodo]

Yeah, these kinds of motors have been around for ages: 8-pole with rotor resistors, and 4-pole with open slip rings.
Quote: only works when the rings are closed (8 poles), when opened" there is no rotor current, no rotor magnetic field and no torque
But the thing is, what if the rotor winding's a closed loop, like a 2-wye setup like we've got here?
I'm guessing that's the case, since the OP still hasn't shared a wiring diagram of how they actually wound the rotor.
But you can't just slap any closed loop on the rotor and expect it to work as a 4-pole motor. To figure out the rotor wiring, you also need to know the stator winding configuration, which we also haven't seen.
Bottom line, these motors are a real pain, and it's super easy to mess up the diagrams, both for the stator and the rotor.

Motor Repair and Design