# How to supply electrical current to a motor-powered rotating shaft?

I want to supply electrical current to a motor-powered rotating shaft. The current supplied is of the order of 400-600 amperes (AC or DC). In what ways can it be done? Shaft speed is around 1400 RPM. The voltage applied is 220 volt for AC. For DC, the voltage will be lower. I am on the conceptual stage, so I may be missing on few details. I have a hybrid power source that can supply DC as well as AC as output. So I require this setup so as to work on both as the need arises.

• What voltage does the rotor shaft circuit require? Is it DC or AC. If AC, what frequency? – Andy aka Jul 18 '18 at 16:50
• What is the shaft speed? You can add these details to your question by clicking 'edit' in the bottom left. – Jack B Jul 18 '18 at 16:51
• @Andyaka 220 volts for AC and below that for DC. – Numero Uno Jul 18 '18 at 16:53
• So you want to supply 132 kVA to a rotating shaft AND using a technique that can also work with DC eh? I think you might need to explain precisely what your setup is and what you are trying to achieve. You might also state what your power source is. – Andy aka Jul 18 '18 at 16:55
• Are you aware of the power limitations usually imposed at 220 volt - 132 kVA is more VA than most 3 phase supplies can give. Think again what you want to deliver to the rotating shaft and give more detail. At the moment, this question appears to be badly thought out and potentially XY in nature. – Andy aka Jul 18 '18 at 17:27

The obvious approach is to either use a slip ring

or a roll ring.

1000A at 1400 RPM is possible for either approach (do your own thorough search for commercial suppliers, the links are merely intended to be informative).

The slip ring uses brushes, the roll ring uses spring rollers.

There are other methods possible, but not so applicable for DC. There will be significant electrical noise generated by the moving contacts so if you have sensitive instrumentation nearby it can be affected. The roll ring will likely be quieter electrically. Roll rings are used in the ISS to transmit solar power across a rotating joint.

The way to supply current to a rotating object is with a device called a slip ring. Essentially this is just a brush. You can get slip ring assemblies with many channels, though I suppose if you want the current on the shaft itself, you would need one one-channel slip ring at each end.

• Are there commercially available slip rings that can be used with 400-600 Amperes current ?? I have seen slip rings with rated current of 10 Amps. I do not have much idea about it. Please guide. – Numero Uno Jul 18 '18 at 17:11
• We do not generally give shopping advice here. High-current slip rings are used for wound-rotor induction machines. Manufacturers of such machines more than likely manufacture them or have them manufactured for their use. I strongly suspect you will need to have them made for your project. – Charles Cowie Jul 18 '18 at 17:26
• Current ratings for slip rings are a problem. You'll weld your brushes right to the shaft. – Scott Seidman Jul 18 '18 at 20:17

You can also generate the current on the shaft itself by putting a set of generator rotor coils there.

This is done in alternators to get the field current for the rotor, while also allowing a small regulator current. To get DC, the rectifier is on the shaft rotating. Not usually high currents then.