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Post by don on Mar 4, 2020 18:12:13 GMT
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Post by coldspaces on Mar 4, 2020 18:21:17 GMT
Wow more great information! Thanks for posting!!
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Post by turbokinetic on Mar 5, 2020 4:04:43 GMT
Thanks, this is good info! I really appreciate your sharing these books with us. |
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Post by don on Mar 31, 2020 12:15:31 GMT
The notable difference I see in the difference between a split phase motor and the GE three wire condenser motor is the inverse winding resistances of the start/run windings.
Conventional textbook/classroom/job motor experience is that the run winding will have less winding resistance and turns and the start winding will have more resistance and turns. The lines of flux from the alternating AC current in the run winding will induce a voltage higher than the source voltage in the start winding just like a voltage transformer. If a voltage relay were used in the circuit it would open and remove the start winding from the circuit at the design rise point of the voltage induced into the start winding.
The three wire GE motor has more resistance in the run winding and less resistance in the start winding resulting in a step down transformer effect.
Thus we have a start winding of 70 volts. Maybe this is done as the start winding is left in the circuit?
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Post by turbokinetic on Mar 31, 2020 13:27:07 GMT
The notable difference I see in the difference between a split phase motor and the GE three wire condenser motor is the inverse winding resistances of the start/run windings.
Conventional textbook/classroom/job motor experience is that the run winding will have less winding resistance and turns and the start winding will have more resistance and turns. The lines of flux from the alternating AC current in the run winding will induce a voltage higher than the source voltage in the start winding just like a voltage transformer. If a voltage relay were used in the circuit it would open and remove the start winding from the circuit at the design rise point of the voltage induced into the start winding.
The three wire GE motor has more resistance in the run winding and less resistance in the start winding resulting in a step down transformer effect.
Thus we have a start winding of 70 volts. Maybe this is done as the start winding is left in the circuit?It's somewhat of an abstract concept but it has to do with the compressor motor's start to run winding turns ratio. In the compressor motor, the start winding has higher resistance in ohms when measured with a meter by passing DC current through it. This is due to smaller wire used to make the start winding. However, when compared to the run winding; the compressor's start winding has fewer turns of wire in each coil pole. As the compressor is running at normal speed and the start relay is not injecting power into the start winding; the spinning rotor will induce a voltage in the start winding. This voltage will (more or less) be proportional to the input voltage to the Run winding, factored by the turns ratio between the start and run winding. It's similar to a transformer in some ways. So when the compressor is running, it is putting out a 90 degree phase-shifted voltage, generated from its start winding, which is less than the input to the run winding. Most polyphase motors don't differentiate between the windings by calling them Start and Run. The would just be called A and B; or A, B, and C if 3-phase. In a conventional polyphase system, the voltages are equal for each phase, so the motor's windings are going to be made of equal numbers of turns of wire, of equal size. For these motors to be magnetically in balance, they need an equal voltage on all phases for the motor's identical winding poles to work most effectively. When using the compressor motor as a source of 2-phase power, there is a compromise. To start, the compressor motor has to have different winding turns for the start winding to do its job. In this case, the 2-phase power source which is available from the compressor; has different voltages for each of the two phases. In order for the fan motor to be magnetically balanced between the two phases, it needs to have less turns of winding on the phase which is powered by the lower voltage, and more turns of winding on the phase powered by the higher voltage. When you measure the DC resistance of the winding with less turns, it will have less resistance since it is designed for a lower voltage. It's not because the fan motor has dedicated start and run windings. In fact, both windings are essentially "run" windings like the windings of a 3-phase motor. It's just that the 2-phase condenser fan motor is custom wound to work with a 2-phase power source which has different voltages for each phase. But both windings in the fan motor are actually powering the motor at all times. Hope this is a good explanation! It's a little abstract I know.  Sincerely, David |
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