Kind of a dumb question

[holler]

I've got a question that I don't have an answer to. Do the older three phase sirens (Model 5, SD-10, xt22, STx-10) have brushes and a commutator in the motor for startup like their single phase counterparts, or do they operate on induction alone?

Just wondering since the position of the windings in three phase motor might provide enough startup torque alone.

[ver tum]

I would think they would still have brushes andcommutators. The reason I say this is because I was just told the other day that all of the older sirens here in Louisville are three phase, and I know that we've had some Thunderbolts that have needed new brushes. If the chopper motor on a three phase TBolt is single phase though, I could be wrong.

[Franz?]

There is no need or use for brushes in a 3? motor.

If somebody is "replacing" brushes in 3? motors as part of a maintainence program they are scamming somebody.

[kx250rider]

If the chopper motor on a three phase TBolt is single phase though, I could be wrong.

Only the blower is 3-phase. The chopper and rotator are single phase motors. However, I can't remember what voltage. The chopper is fed by a multi-tap transformer, whose primary comes off one leg of the 3-phase. If nobody else has a firm answer on the voltage of the 2 small motors, I can check the tags on mine later.

Charles

[JasonC]

Single phase motors that are split phase or capacitor start do not need brushes as well as any three phase motor. The only single phase motors that need brushes are repulsion-induction and universal type motors as well as DC motors.