With an uncoupled motor I know that as you reduce the supply voltage the current will decrease due to the fact that most of the current is magnetizing current and very little is current across the rotor producing torque. So since the torque current is so small, when you reduce the voltage the magnetizing current drops (less flux density?) and therefore the overall motor current drops.
How much or what percent can you decrease the supply voltage on an uncoupled motor to where it will still turn? Is there a minimum value for which below it will not turn?
I have seen that for determining values of Rm paramater an unloaded motor is run at a reduced voltage that usually provides full load current. How come at a very reduced value of voltage with motor unloaded the current eventually increases instead of decreasing as we said above? Is this because the torque required to overcome the friction and winding losses decreses with reduced voltage, and therefore current must increase to keep motor spinning?
How much or what percent can you decrease the supply voltage on an uncoupled motor to where it will still turn? Is there a minimum value for which below it will not turn?
I have seen that for determining values of Rm paramater an unloaded motor is run at a reduced voltage that usually provides full load current. How come at a very reduced value of voltage with motor unloaded the current eventually increases instead of decreasing as we said above? Is this because the torque required to overcome the friction and winding losses decreses with reduced voltage, and therefore current must increase to keep motor spinning?