# Ambitious idea : swapping brushes for slip rings and solid state inverter



## major (Apr 4, 2008)

Dalardan said:


> Is it worth a try? Am I wrong on the whole line?


Hi Dalar,

Worth a try? Not in my opinion.

Slip rings are used to pass current to a rotating field, as in your car's alternator. Commutators used in DC motors pass as well as switch current to the rotating armature. Way different animals.

Regards,

major


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## Dalardan (Jul 4, 2008)

Well, I might have explained myself not correctly.

My idea would be to use to slip rings to pass current to the rotation armature and to switch this current using some kind of solid state inverter, thus sending an alternative current through the slip rings, synchronized with the angular position of the rotor. This way, the stator would have a DC input and the rotor would have a monophase AC one (trapezoidal or sine wave), like with the mechanical commutator. Note that it could also be the opposite like in a car alternator.

I do think it would make the series wound motor behave like a AC synchronous motor.

Dalardan


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## major (Apr 4, 2008)

Dalardan said:


> My idea would be to use to slip rings to pass current to the rotation armature and to switch this current using some kind of solid state inverter, thus sending an alternative current through the slip rings, synchronized with the angular position of the rotor. This way, the stator would have a DC input and the rotor would have a monophase AC one (trapezoidal or sine wave), like with the mechanical commutator.


O.K. So you would need 37 pairs of slip rings?


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## Dalardan (Jul 4, 2008)

Hum... well it's the first way of seeing this (which is, I agree, not a good idea to try).

I should then see how the 37 plates of the commutator are connected to the rotor. Are each pair of them an independant coil ? (And thus, why is the number or plates not a multiple of 2) Or is there only 1 coil, and half the plates are connected to the same end, the other plates are connected to the other end, and they alternate on the commutator? 

Is it like in AC motors where there are 2 poles motors, 4 poles motors and so on? If I do remember, there are motors that have 4 set of brushes touching the commutator, maybe more. This could be emulated by having some plates connected to the same slip ring because they are all driven simultaneously. 

Hum... I should find more information on how a commutator works, I do feel like I'm getting it wrong.

Dalardan


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