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I'm in school and the subject of wound rotors has come up in my motors class. The class mostly deals with squirrel cage motors but WRIMs are part of the course material too. Nobody in my class has ever seen one except me, and that was once when I was a first year. It was maybe 100-125 hp, and ran a dust extractor in an old furniture factory in Ontario. We were there to relocate the starter and I remember watching it start up after. Several contactors closed and opened in sequence as the motor spun up.

Now that I actually know how one of these works, I have to ask, are these still widely in use now that we're well into the VFD era? Can you still buy one, aside from really huge sizes? Is there any reason to?
 

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I only worked on a few of those and were in the 900hp range, they do use less power to start and as you have seen most of the larger size have multiple motor starters that sequence in the winding's so as not to brown down the grid or get a fine from the POCO.
 

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I'm in school and the subject of wound rotors has come up in my motors class. The class mostly deals with squirrel cage motors but WRIMs are part of the course material too. Nobody in my class has ever seen one except me, and that was once when I was a first year. It was maybe 100-125 hp, and ran a dust extractor in an old furniture factory in Ontario. We were there to relocate the starter and I remember watching it start up after. Several contactors closed and opened in sequence as the motor spun up.

Now that I actually know how one of these works, I have to ask, are these still widely in use now that we're well into the VFD era? Can you still buy one, aside from really huge sizes? Is there any reason to?
I'm not a commercial electrician these days so I do not know if they are still used, from to articles I just read it seems that there are some advantages in using them such as applying resistance at start up to lower the inrush current. A long slow start up.

http://www.allaboutcircuits.com/vol_2/chpt_13/8.html

http://ecmweb.com/content/wound-rotor-motors-high-torque-and-adjustable-speed




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THE "BIG RED MACHINE"
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I think they have high torque starting capabilities
 

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Now, one of the old guys!
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At the shop I worked in 30 years ago, we used 750hp and 1000 hp wound rotor motors on rubber mills. The starting load of these motors is so high if you did not step the motor up it would trip the mains. These were huge motors, you could sit inside the end bell to clean the windings and service the bearings, commutator and so forth. We had a guy get seriously injured working in one of the relay cabinets. Never did find out what happened but there was an explosion and huge arc flash. This was long before arc flash gear. He never was right afterwards. Ours were 4160 volt motors.
 

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cool cat
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We are still maintaining a 1924 model 600hp 2400 volt wound rotor motor.It is used as a hoist down about 2400 feet.Still use the old controller with 250 volt dc coils to pull in the steps of resistors.The hoist motor was re-wound about 15 years ago.Controller still works ,we have replacement coils on hand in case but so far there has been no repacement for at least 10 years.Mg set provides the 250 volt dc control power.Working on a 250 volt power supply by using a full wave rectifier.Bought the rated diodes and installed are waiting for a slow period to try it out.
 

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At the shop I worked in 30 years ago, we used 750hp and 1000 hp wound rotor motors on rubber mills. The starting load of these motors is so high if you did not step the motor up it would trip the mains. These were huge motors, you could sit inside the end bell to clean the windings and service the bearings, commutator and so forth. We had a guy get seriously injured working in one of the relay cabinets. Never did find out what happened but there was an explosion and huge arc flash. This was long before arc flash gear. He never was right afterwards. Ours were 4160 volt motors.
:eek:
 

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They are still made, but are made to order, and mostly for retrofit to existing systems on very large motors where the cost to completely re-engineer everything to use a VFD is prohibitive, or where the physical dimensions make it so tht a new SCIM would not fit. WRIMs could more easily be made in a "pancake" type frame; thin and tall, as opposed to new SCIMs that have that barrel shape. So can you still buy a 100HP WRIM? Yes, if you can wait 3-6 months for it. Does that still make sense? No.

They did tend to offer high starting torque with lower input current, something that in the pre-VFD days was an either/or situation. But modern vector control VFDs can now match anything a WRIM could do.
 

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Wow, that was informative. When I grow up I want to be a JRaef.

So how long ago did VFDs make WRIMs totally obsolete? The mid 90s?
Louis-Allis built them for OEM and replacement use, up to the time they went out of business in 1998. IIRC, they were only up to 100 HP.
They still were preferred for hoisting applications. :thumbup:
 

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Surprisingly wound rotors are still in use today even with "VFD" saturating the market. A lot of Foundry's and coal processing facilities still use wound rotor motors on overhead cranes., I worked in a facility that had 30 overhead cranes of which all had wound rotor. The larger wound rotors are not as common these days but 75Hp through 150 HP for bridge/hoist motors are. Since larger more efficient AC induction motors are available it makes it much easier to use one of the these and a soft start than it is a wound rotor. I although still prefer wound rotors on overhead cranes when compared to AC with VFD. The ac motor just does not have the "Guts" to pickup extremely large loads, although they can but you can tell they struggle like hell. A wound rotor on the other hand I've seen pickup up loads in excess of 100 ton and growl while doing it. Wound rotors are and will always be a timeless part of the industrial revolution.

JC
 

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The last episode of Gold Rush actually has one on Tony's dredge.. The electrician he brought in was in a little disbelief when he saw the resistor bank in a heap on the ground... He said his dad was the last electrician to do any wiring on a dredge in the Yukon.. He wound up getting it to run at one speed and breathed some life into the dredge...
 

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The last episode of Gold Rush actually has one on Tony's dredge.. The electrician he brought in was in a little disbelief when he saw the resistor bank in a heap on the ground... He said his dad was the last electrician to do any wiring on a dredge in the Yukon.. He wound up getting it to run at one speed and breathed some life into the dredge...
I saw that, and I was thinking "Ooh, Ooh, I know how to make that work!" But no matter how loudly I yell at those guys on that show, they never listen...
 

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The main sewer plant for Reno and Sparks has 4 - 350HP vertical-shaft 12 pole motors in the headworks. The plant was built in the 60s, and 3 of these motors are 2300 volts wound-rotor type. The 4th one is basic 480, used to be started with an autotransformer, now it has an electronic soft-start.

The 2300 volt ones use a resistor bank to vary the speed.

They still work just as they have for over 50 years.

Point of interest; when using a resistor bank to vary the speed of a wound-rotor motor, it will operate at close to synchronous speed while unloaded, regardless of the selected speed. They need to be loaded in order to run at a slower speed.
 

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The last episode of Gold Rush actually has one on Tony's dredge.. The electrician he brought in was in a little disbelief when he saw the resistor bank in a heap on the ground... He said his dad was the last electrician to do any wiring on a dredge in the Yukon.. He wound up getting it to run at one speed and breathed some life into the dredge...
I saw it too. I hope it never runs. Tony Beets is an asshole.
I was asking myself and the TV since he bought that dredge if he had checked whatever powered it.
I still have no idea.
Is it run by diesel? Somethings got to turn that shaft and there ain't no POCO within miles?
What turns this dredge motor?
 

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I saw it too. I hope it never runs. Tony Beets is an asshole.
I was asking myself and the TV since he bought that dredge if he had checked whatever powered it.
I still have no idea.
Is it run by diesel? Somethings got to turn that shaft and there ain't no POCO within miles?
What turns this dredge motor?

There's got to be a big genny that he plans to keep on board to power it.

With that motor now only able to turn at one speed, and with the possibility that the motor is generating some serious current during start-up, I would think in future shows of Gold Rush, we will see that come back to bite him in the ACE...haha
 

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I worked on one here in the Motherlode of California that was resurrected just like that one about 6 years ago, it was fascinating, loved every minute of that project. The owner was an aggregate (gravel) crushing outfit that had bought an old mining operation and was using the old tailings piles as crushing stock for a few years using a drag line. But every now and then they found flecks of gold in the wash plant and decided it was worth rebuilding the floating mining dredge that was already there but had been abandoned since the 30s. In their case they didn't have to dismantle it and move it, it was still floating in the pond. But they did completely gut all the old mechanical controls and modernize it, I worked on the MCCs and VFDs they added. They get enough gold out of recycling the old tailings to pay for ALL of the expenses of the gravel plant, so the crushed gravel they sell is all gravy. It's a sweet deal really.

What they do for power is a DG set on board. Not sure what Tony Beeks is planning on, I didn't see one there or they didn't bother to show it. But he could have the DG on shore and feed the dredge with portable cords. They don't advance very fast and if he deposits the tailings behind him, he can just move the DG set, probably about once/month at most, onto the new shoreline it creates behind itself.
 
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