BLDC motor eliminates the carbon brush and slip ring structure, so it can run at low speed and high power. In addition, it is much smaller in weight and volume than brushed DC motors, the corresponding moment of inertia can be reduced by 40% to 50%. The motor has soft start soft stop, good braking characteristics, so it will save the original mechanical brake or electromagnetic brake device. The motor itself has no excitation loss and carbon brush loss, eliminating multi-stage deceleration, the overall power saving rate can reach 20% ~ 60%.
The speed control of BLDC motor is essential for making the motor work at desired rate. The speed can be controlled by controlling the input dc voltage. When the motor works in normal mode or runs below rated speed, input voltage of armature is changed through PWM model. When the motor is operated above rated speed, the flux is weakened by means of advancing the exiting current.
