BLDC vs AC Motor - Comparison between BLDC motor with Induction Motor

Comparison between BLDC motor with Induction Motor:

In this Post we will see the comparison between BLDC with Induction motor(BLDC vs AC Motor ). Before Proceeding further it is recommended to refresh about the basics of both the motors. Please click here to know about the basics of BLDC Motor.  

BLDC -  Brushless DC Motor. It is a Permanent-Magnet Synchronous Machine ( It is not a DC motor). It is powered from variable DC source, but it is internally an AC motor.

BLDC Motor Vs AC Induction Motor:

BLDC MotorAC Induction Motor
The speed/torque characteristics is flat in nature.
It enables operations at all speeds with rated load.
The speed/torque characteristics is non linear in nature.
It enables lower torque at lower speeds.
Output power/ Frame size is high.
Because it has permanent magnets on the rotor, the smaller size can be achieved for a given output power.
Output power/frame size is moderate.
Because both stator and rotor have winding, output power to size is lower than BLDC.
The rotor inertia is low.
This enables better dynamic characteristics.
The rotor inertia is high.
This enables poorer dynamic characteristics.
The starting current is rated.
No special starter circuit is required. 
The starting current is approximately up to 7 times of rated.
Stator circuit rating should be carefully selected. It normally uses a star delta starter.
A controller always required to keep the motor running.
The controller can be used for variable speed control.
No controller is required for fixed speed.
A controller is required only if variable speed is desired.
No slip is experienced between stator and rotor frequencies.The rotor runs at a lower frequency than the stator by slip frequency and slip increases with load on the motor.

You may also like to read:

BLDC vs DC Motor – Comparison between BLDC Motor and Conventional DC Motor
Squirrel Cage Induction Motor vs Slip Ring Induction Motor
Comparison of Inverters: VSI vs CSI
Difference between AC and DC Drives  

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5 Responses

  1. williamHu says:

    good point,What's advantage especially in pump application?

  2. Abhi says:

    it was quite helpful.....
    Thanks for the info.....

  3. puvi says:

    what about effeciency?

    • Jigar Purohit says:

      Talking in regards to efficiency, BLDC motor has almost 90 to 96 % of efficiency at any condition if its well design. Now about Induction Motor it has higher efficiency at higher power range as well at higher rpm.
      Now through the point of application (considering case in Electric Vehicle), if you are using BLDC of rating 3kw and 3000 rpm it's efficiency will more than 92% and the same rating of I.M will give you the eff. of 70 to 80%.
      In short Induction Motors are more reliable for high performance applictions.

  4. Peter Torhan says:

    Hello, how to compare bldc and ac motor? Is the same performance in doing some work by AC 150w , 3000rpm and BLDC 150w and 3000rpm? thank you for comments

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