The difference between DC brushless motor and AC induction motor

There are various kinds of motors, and the energy they produce can promote the operation of the equipment. There are almost differences between different motors in all aspects. The difference between DC brushless motor and AC induction motor is not only the literal difference, but also in many aspects

1. Output power / volume:

BLDC motor: high. Because the rotor is made of permanent magnet, it can achieve a small volume for a given output power.

Induction motor: medium. Because both stator and rotor have windings, the ratio of output power to volume is lower than BLDC.

2. Speed / torque characteristics:

DC motor: flat. Under the condition of load rating, it can work normally at all speeds.

AC induction motor: nonlinear. The torque is also low at low speed.

3. Control requirements: to keep the motor running, the former always needs a controller, which can also be used to control the speed. In the latter, the controller is not needed for fixed speed, only when the speed needs to be changed.

4. Starting current:

Rated value. No special starting circuit is required.

About seven times the rating. Proper starting circuit should be selected carefully.

5. Rotor inertia:

DC brushless motor: small. Dynamic transformation is better.

Induction motor: large. Poor dynamic characteristics.

6. Differential frequency:

BLDC motor: the frequency of stator and rotor field is equal.

Induction motor: when the operating frequency of rotor is lower than that of stator, the difference is the difference frequency, which also increases with the increase of motor load.

In fact, both of them are not the same kind of motor in essence, and one of them produces direct current and the other is alternating current. There are also differences in other aspects. The intention is to correctly distinguish the two when selecting the motor.