The motor on my Aciera F3 is a two-speed 3 phase with independent windings (i.e. not a Dahlander motor) and previous owner(s) has altered the wiring (e.g. contactors gone). I have traced the wiring, and found that when the switch is set for high speed, the low speed winding is shorted (details at point A below).
Is there really an advantage to this? I would think it could even be a disadvantage/harmful as this would induce currents in the low speed (unused) winding. I have found factory wiring diagrams and none show this feature, i.e. the unused winding is left open.
Has anyone any experience of wiring a 3 phase, 2-speed motor like this? Am I right in assuming that will result in currents being induced in the shorted low-speed winding when running at high speed?
Specifics/details:
A: When the speed selector switch is set to hight speed the terminals u, v, w are energized (connected to the mains), and terminals x, y, z are connected/shorted together. The opposite is not true: when x, y, z are energized (connected to mains), the high speed terminals u, v, w are left open (not connected to anything).
B: The badge on the motor is missing, but the speed ratio between low/high is 1:4 (according to speed label on the mill), so it cannot be a Dahlander type motor as this would have a 2:1 ratio.
C: The terminals (6) on the motor are labelled z, x, y in one row, and u, v, w in one row. As measured with ohmmeter there is no connection between the x,y,z terminals and the u,v,w terminals. (Resistance between x and any of u,v,w is infinite.) Again demonstrating that we have two sets of independent windings. The resistance within the groups is approx 8 ohms for the high speed terminals (e.g. u-to-w reads 8 ohms) and the low speed is around 37 ohms (e.g. y-to-z reads 37 ohms).
D: I have not tried to run the motor with this wiring as I'm just reassembling the mill. (Had to take it apart to bring it down in the basement after buying it two years ago.)
Is there really an advantage to this? I would think it could even be a disadvantage/harmful as this would induce currents in the low speed (unused) winding. I have found factory wiring diagrams and none show this feature, i.e. the unused winding is left open.
Has anyone any experience of wiring a 3 phase, 2-speed motor like this? Am I right in assuming that will result in currents being induced in the shorted low-speed winding when running at high speed?
Specifics/details:
A: When the speed selector switch is set to hight speed the terminals u, v, w are energized (connected to the mains), and terminals x, y, z are connected/shorted together. The opposite is not true: when x, y, z are energized (connected to mains), the high speed terminals u, v, w are left open (not connected to anything).
B: The badge on the motor is missing, but the speed ratio between low/high is 1:4 (according to speed label on the mill), so it cannot be a Dahlander type motor as this would have a 2:1 ratio.
C: The terminals (6) on the motor are labelled z, x, y in one row, and u, v, w in one row. As measured with ohmmeter there is no connection between the x,y,z terminals and the u,v,w terminals. (Resistance between x and any of u,v,w is infinite.) Again demonstrating that we have two sets of independent windings. The resistance within the groups is approx 8 ohms for the high speed terminals (e.g. u-to-w reads 8 ohms) and the low speed is around 37 ohms (e.g. y-to-z reads 37 ohms).
D: I have not tried to run the motor with this wiring as I'm just reassembling the mill. (Had to take it apart to bring it down in the basement after buying it two years ago.)