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A Dahlander motor (also known as a pole changing motor, dual- or two speed-motor) is a type of multispeed three-phase induction motor, in which the speed of the motor is varied by altering the number of poles; this is achieved by altering the wiring connections inside the motor. It is named after its inventor Robert Dahlander (1870–1935).
A Dahlander motor achieves different speeds by switching the configuration of the electrical windings, indirectly adding or removing poles and thus varying the rotor speed. The poles can be varied at a ratio of 1:2 and thus the speed can be varied at 2:1. Normally, the electrical configuration of windings is varied from a delta connection (Δ) to a double star connection (YY) configuration in order to change the speed of the motor for constant torque applications, such as the hoists in cranes. Star connections (Y) varied to double star connections (YY) are used for quadratic torque applications, such as pumps.
Instructions:
The coiling diagram used for this 24 slot stator circuit is:
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Instead of a Δ/YY diagram, it's made as a Y/YY diagram.
Each pair of slots (1+2, 5+6, 17+18 etc.) has 1 pair of LEDs, for ease of use and visibility, since the paired slots always have the same direction of current flow. One LED is red, the other is blue. The red LED shows a "North-pole", the blue LED a "South-pole".
A sine wave of phase 1 is shown for reference.
To get into "low RPM" (Y circuit), make sure both switches are off, then switch on the left.
Notice how 2 red LEDs and 2 blue LEDs emit light per phase. These are 180° shifted per color emitted.
For the set of phase 1 this means, when phase 1 is in the positive period, LEDs 1 and 7 are red and LEDs 4 and 10 are blue. When phase 1 is in the negative period the colors are the other way around.
Try to follow a LED around and notice it takes 2 full periods of the sine wave to complete one full rotation of the "rotor".
The stator now has 4 poles, 2 North and 2 South poles.
Also notice the followed LED jump ahead 2 slots (1 LED pair) when the next phase is energizing its LEDs.
To get into "high RPM" (YY circuit), make sure both switches are off, then switch on the right.
The switched off relays now create the second "Y" connection.
Now, still 2 red LEDs and 2 blue LEDs emit light per phase, however, these are now 90° shifted per color emitted.
For the set of phase 1 this means, when phase 1 is in the positive period, LEDs 3 and 12 are red and LEDs 6 and 9 are blue. When phase 1 is in the negative period the colors are the other way around.
Try to follow a LED around and notice it now takes 1 full period of the sine wave to complete one full rotation of the "rotor".
The stator now has 2 poles, 1 North and 1 South pole.
Also notice the followed LED jump ahead 4 slots (2 LED pairs) when the next phase is energizing its LEDs.
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