Quote
genn
If we see the motor datasheet its resistance is 1ohm and rated current is 4A, so that the consumed power is P =I2R = 16W. So if we power the driver with a 48V supply the motor is taking almost I= 16/48 = 0.33A which i can see directly from the power supply(the power supply will show how much current the circuit draws). Upto this everything is ok(Standstill). But when we start rotating the motor the current increases. If we keep on increasing the speed, current increases to a point from where it starts decreasing.
What happens is that as you increase the motor speed and the amount of load on the motor, the motor produces a back EMF and the power consumed increases to include the power that the motor is delivering to the load. That's why the current taken from the power supply increases, even though your constant current drivers are still supplying 4A to the motor.
Above a certain speed, the drivers are unable to switch the current in the phases fast enough using a 48V supply, so the current never reaches 4A and the torque is reduced. To maintain torque at higher speeds, you would need to increase the power supply voltage (if your drivers can take more voltage).