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Hi,



1)

I understand how a DC Motor Rotation is reversed by simply reversing the Polarity of the Applied DC Voltage.

I am Clueless as to how a Model Train AC Motor Rotation is reversed. AC Voltage is a Sine Wave.

Electrically, how is the Model Train AC Motor Rotation Reversed ?



2)

I read or possibly misread that a Model Train AC Motor will operate, actually smoothly, on DC  Voltage.

Is that correct ?



Thank you,

Norman

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With the AC motor with a single field winding (most common), you just reverse the two brush leads to reverse the motor direction.

With the AC Motor with a dual-field winding, you change which field winding is connected to one of the brushes.

In either case, the field coil is frame ground, the other lead of the field coil goes to one motor brush, and the hot side of the power goes to the other brush.

Yes, these are also called "Universal motors", and will run on DC the same as AC.  To reverse direction, you still swap the brush leads, swapping the power to the whole brush/field wiring would not reverse the motor.

A DC motor has a permanent magnetic field created by a magnet, and is reversed by reversing the polarity going to the brushes. An AC motor has windings in place of that magnet, and is reversed by keeping the polarity of the brushes (or field) the same while reversing the polarity of the other. So when an AC motor is reversed one input remains the same while the other is reversed, allowing it to swap directions because the brushes and field are now in opposite phases.

Yes, an AC motor works on DC just fine, however reversing the polarity won't reverse the motor.

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