×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

2 hall sensor and 3 phase BLDC motor

2 hall sensor and 3 phase BLDC motor

2 hall sensor and 3 phase BLDC motor

(OP)
Hi all,I get a brushless permanent magnet motor used on autobike, with 2 hall sensor, but 3 phase of delta connection.
its back EMF is sinusoidal well. And I know most of BLDC motor use 3 hall sensors to detect the rotor position and sent the signal into controller. also its back EMF is trapezoidal. But this motor is much different, could anyone give a answer about it?
Thanks  

RE: 2 hall sensor and 3 phase BLDC motor

I've seen many 3 phase BLDC motors with 2 hall effect sensors.  All it is doing is sensing the rotor position.  You can control a sensored motor with a sensorless controller.  Sinusiodal controllers are smoother and will have reduced cogging effects, however trapezoidal seems to be the standard for applications in vehicles such as yours.  The motor back EMF will still be sinusioidal.  I haven't seen any that were trapezoidal.

What is so different about the motor that has you concerned?  Also, if not already in place, when using longer battery leads , it is a good idea to place some extra capacitors at the input terminals of the controller.  Varying speeds with a trapeziodal controller tends to be hard on the controller perhaps due to the inductive effect of the longer wires.  

------------------------------------------------------------------------
If it is broken, fix it.  If it isn't broken, I'll soon fix that.

RE: 2 hall sensor and 3 phase BLDC motor

(OP)
Thanks for your suggestion. Actually I'm not sure that when I change the 2 sensors to 3 sensors and use a trapezoidal controller to drive the motor, the result would be what?  its out power increase some,torque ripple increased,etc?  sensorless controller may could drive the motor also. But,and you mean that these 2 sensors are used ONLY to detect the rotor positon for the starting time, after motor speed is high enough then switched to sensorless controller mode?

RE: 2 hall sensor and 3 phase BLDC motor

Wow, this must really be a cost-optimsed design.
Yes, you can get away with using only two sensors, however starting the motor is a problem, as you don't know exactly where the rotor is.
I would expect the controller for this motor to apply a rotating three-phase field to get the rotor turning, and as soon as this is established then use the signals from the two sensors to synthesise the third phase.
If this is some kind of constant-speed application it would be OK.

Benta.

RE: 2 hall sensor and 3 phase BLDC motor

Guys,
this isn't cost-optimized design - I hope this is 2 sine analog Halls instead 3 digital Halls! Some sine servo amp may use them for sinusoidal commutation of PMBL motors.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources