The reason for this is that the motor is designed to operate at a specific voltage and frequency. When the voltage is reduced, the motor's magnetic field strength is also reduced, which in turn reduces the amount of torque that the motor can produce. This results in a decrease in the motor's speed and power.
The amount of decrease in speed and power will depend on the specific motor design and the amount by which the voltage is reduced. In general, a 10% reduction in voltage will result in a 5-10% reduction in speed and power.
If you are planning to operate a 3-phase 440-volt 50Hz motor on a 380-volt supply, it is important to make sure that the motor is capable of handling the reduced voltage. You should also check with the motor manufacturer to see if there are any specific precautions that you need to take.
In some cases, it may be necessary to use a voltage booster to increase the supply voltage to the motor. This will help to ensure that the motor operates at its full rated power and efficiency.
