Motor ?

series/shunt/compound

Lancie1 said:

It appears that the slip rings are 3-phase, 1 phase bare, 1 marked yellow, 1 marked blue. If so, this could be a wound-rotor motor, with a rotor having a coil fed by slip rings (instead of the usual induced-current rotor). The speed of a wound-rotor motor can be changed by changing the resistance between A-B, B-C and C-A of the wound rotor leads. Before electronic VFDs, wound rotor motors were used in cranes and other large loads.

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Yes, I believe that's what this is. I have the German drawings and I translated it to "occasioned resistance", so that tells me it is wound rotor and they were controlling the speed on startup. After a timer expires, there is a contactor which shorts out the three wires.

Lancie1 said:

It appears that the slip rings are 3-phase, 1 phase bare, 1 marked yellow, 1 marked blue. If so, this could be a wound-rotor motor, with a rotor having a coil fed by slip rings (instead of the usual induced-current rotor). The speed of a wound-rotor motor can be changed by changing the resistance between A-B, B-C and C-A of the wound rotor leads. Before electronic VFDs, wound rotor motors were used in cranes and other large loads.

Click to expand...

Definitely a Wound Rotor Induction Motor, too many stator connections to be DC, too many rotor connections to be synchronous. So your control cabinet would have likely had a set of contactors for the slip ring portion, the one on the left, which is what you may have interpreted as being Wye Delta, but it is not. The contactors go to external resistors that are turned on with the stator, then in stages relating to the desired torque /speed, you short them out. The lower the resistance, the higher the torque/speed, so the final stage is for the resistors to all be shorted out. That last contactor then looks like the shorting contactor of a wye delta starter.

If, as is obvious, you have never seen a WRIM before, you will have a learning curve ahead of you to get it running, and that may be especially difficult if the resistors didn't come with the machine, as often the case because people don't understand them. The motor can be run via a VFD if you use a good quality Vector drive, and take the motor to a rewind shop and have them short out the slip ring connections on the rotor. Do not try it yourself, it has to be balanced again afterward and do not just short them externally, because as the slip rings and brushes wear out, it affects the ability to use the VFD. Also don't use a cheap VFD even if it says it is vector capable, many of the el-cheapo brands just lie about that. To avoid burning up the motor by starting it with the rotor shorted, the VFD must maintain very accurate control of the current and that is where the lies from the bottom feeders bite you in the butt.

jraef said:

Definitely a Wound Rotor Induction Motor, too many stator connections to be DC, too many rotor connections to be synchronous. So your control cabinet would have likely had a set of contactors for the slip ring portion, the one on the left, which is what you may have interpreted as being Wye Delta, but it is not. The contactors go to external resistors that are turned on with the stator, then in stages relating to the desired torque /speed, you short them out. The lower the resistance, the higher the torque/speed, so the final stage is for the resistors to all be shorted out. That last contactor then looks like the shorting contactor of a wye delta starter.

If, as is obvious, you have never seen a WRIM before, you will have a learning curve ahead of you to get it running, and that may be especially difficult if the resistors didn't come with the machine, as often the case because people don't understand them. The motor can be run via a VFD if you use a good quality Vector drive, and take the motor to a rewind shop and have them short out the slip ring connections on the rotor. Do not try it yourself, it has to be balanced again afterward and do not just short them externally, because as the slip rings and brushes wear out, it affects the ability to use the VFD. Also don't use a cheap VFD even if it says it is vector capable, many of the el-cheapo brands just lie about that, to avoid burning up the motor by starting it with the rotor shorted, the VFD must maintain very accurate control of the current.

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Luckily, the old control cabinet is there, so I can go take out the resistors and use them. The new controls they bought just have an across the line starter. It looks like I'll have to rewire the controls for that motor.

Thanks for the help. This was a new one for me.

Lancie1 said:

It appears that the slip rings are 3-phase, 1 phase bare, 1 marked yellow, 1 marked blue. If so, this could be a wound-rotor motor, with a rotor having a coil fed by slip rings (instead of the usual induced-current rotor). The speed of a wound-rotor motor can be changed by changing the resistance between A-B, B-C and C-A of the wound rotor leads. Before electronic VFDs, wound rotor motors were used in cranes and other large loads.

Click to expand...

T Gibbs said:

Luckily, the old control cabinet is there, so I can go take out the resistors and use them. The new controls they bought just have an across the line starter. It looks like I'll have to rewire the controls for that motor.

Thanks for the help. This was a new one for me.

Click to expand...

This might help get you started.
http://www.lmphotonics.com/slipring.htm
Good luck.

main contactor is connected to stator, right side on picture
left side is on a water resistor bank or wirewound resistors.
A merry goround is always with this type of motor, as the inertia is very high and operation is simple. some of them use a windscreen wiper motor to lower down the plates in the water.
when motor needs running long time on full speed (so for a starter the resistors are shorted after starting.
and yes you can replace it with a VFD, just short the rotor on the rotor itself.

I've got it figured out, now. I have talked to the facilities manager and he is thinking over what he wants to do. He may replace it with a standard 40hp motor. If not, we will have to add a cabinet to install the resistors and contactors in.

I appreciate all the responses. I've learned some stuff today.

T Gibbs said:

I've got it figured out, now. I have talked to the facilities manager and he is thinking over what he wants to do. He may replace it with a standard 40hp motor. If not, we will have to add a cabinet to install the resistors and contactors in.

I appreciate all the responses. I've learned some stuff today.

Click to expand...

I would push you manager to either get the motor rewound with the rotor shorted or just buy a new motor and VFD (or soft start I really don't understand the process).

Wound rotor motors are a thing of the past, no point going down that road unless you absolutely need to.

T Gibbs said:

I've got it figured out, now. I have talked to the facilities manager and he is thinking over what he wants to do. He may replace it with a standard 40hp motor. If not, we will have to add a cabinet to install the resistors and contactors in.

I appreciate all the responses. I've learned some stuff today.

Click to expand...

Just a word of warning; WRIM torque capability is higher for starting / accelerating than a standard off-the-shelf induction motor. Know your machine's torque/speed requirements in detail before choosing to replace that motor, it might take a larger HP rating to get the same performance.

Just one little picky point: wound rotor motors are variable torque motors, not variable speed. The stator always spins at 7200/# of poles so, at no load, all wound rotor motors will run up to sync speed.

Connecting such a motor to a variable torque load gives you variable speed. This is how they are usually used.

jraef said:

Just a word of warning; WRIM torque capability is higher for starting / accelerating than a standard off-the-shelf induction motor. Know your machine's torque/speed requirements in detail before choosing to replace that motor, it might take a larger HP rating to get the same performance.

Click to expand...

+1 on jraef's warning!

Since this is for a press I would be very tempted to use the motor as is. Presses can be hard starting - additionally after the ram activates the motor is full loaded and maybe then some to keep the flywheel turning to correct speed.

Sliprings look to be in pretty good shape. Check the brushes of course and ensure you have an extra set. Take resistance readings of both stator and rotor windings and do a megger to check insulation also. In addition to dust and metal shavings etc this motor has brushes - carbon dust can ground em out right quick. Keep a close eye on brush wear.

IF you replace this motor ensure you get one rated for press duty (type D if recall correct).

Looking at the pictures of the terminations I believe I see only 3 lead for the stator windings. So you have no choice and thus no confusion whether delta or wye connected.
Thus there is no wye start and delta run on the stator.

Of course you must know the motor design voltage.

Since you have all the original controls it should not be too bad to reconnect everything ASSUMING you have factory support - you will need this to know any timing on the resistors and their associated contactors.

Dan Bentler

I am just a contractor hired to install new controls on the press. I pass any problems to the facilities manager or maintenance manager and let them deal with it.

if you buy a new motor you must use a VFD as a normal motor will not be able to start it due to high torque, and it should start slow, as many drums etc are connected, if you start it within 3 seconds the whole machine will be broken the first start,
please have it started the slow way, 30 seconds or more is normal for a wound rotor motor.

Understood. They have many presses in this facility, so they know how they should start. I just wonder why the company that sold them the control system put an across the line starter for it. They specialize in press controls.