AC
Hi Turion,
As the rotor mounted magnet sweeps past the coil it induces one cycle of AC. So when a North magnet approaches the center of the pole (which is the core in the center of the coil), it induces current in the coil causing a N pole on the face towards the rotor. The N pole opposes the N magnet. At TDC (the moment the magnet is centered relative to the pole), there is zero voltage generated in the coil and no current, so the pole face actually becomes a consequent S pole. As the rotor magnet moves away from the pole, it generates opposite polarity so the current is in the other direction in the coil making the pole face S. This S pole then attracts the N magnet on the rotor causing a torque opposing rotation. The coil current always causes a polarity which will result in torque opposing rotation when generating current in that coil. This is the mechanism taking mechanical power from the prime mover.
What I have just described is easily verifiable by connecting a scope across the coil/load resistor. The scope will display voltage. Coil current will have the same profile (waveform) but scaled by Ohm's Law to the ohmic value of the load resistor. Give it a look.
Regards,
bi
Originally posted by Turion
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As the rotor mounted magnet sweeps past the coil it induces one cycle of AC. So when a North magnet approaches the center of the pole (which is the core in the center of the coil), it induces current in the coil causing a N pole on the face towards the rotor. The N pole opposes the N magnet. At TDC (the moment the magnet is centered relative to the pole), there is zero voltage generated in the coil and no current, so the pole face actually becomes a consequent S pole. As the rotor magnet moves away from the pole, it generates opposite polarity so the current is in the other direction in the coil making the pole face S. This S pole then attracts the N magnet on the rotor causing a torque opposing rotation. The coil current always causes a polarity which will result in torque opposing rotation when generating current in that coil. This is the mechanism taking mechanical power from the prime mover.
What I have just described is easily verifiable by connecting a scope across the coil/load resistor. The scope will display voltage. Coil current will have the same profile (waveform) but scaled by Ohm's Law to the ohmic value of the load resistor. Give it a look.
Regards,
bi
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