How to control the speed of bldc motor without reducing voltage. I can able to control the speed by reducing the voltage( pwm signal ). But is it possible to control speed by varying frequency by making voltage as constant.
PWM reduces the average voltage. Trying to control the speed by explicitly controlling the frequency of
commutation will typically just send the motor up in a pall of smoke as the windings burn out. The applied voltage
is opposed by the back EMF from the motor's rotation, so if you prevent the speed from matching the voltage
the current jumps up drastically (just as if you stall the motor). Automatic commutation allows the motor to
speed up to match the applied voltage with back-EMF.
If you instead control the current, you can control the motor speed by the frequency, which is pretty much
how a stepper motor works, since the current limit prevents the heat dissipation in the windings getting
out of hand.
"Trying to control the speed by explicitly controlling the frequency of
commutation will typically just send the motor up in a pall of smoke as the winding burn out."
What you are saying is not to control speed using frequency(by reducing it).
Not unless you have some means to limit the current.
Hi,
How is your BLDC motor being controlled at the moment.
Can you post a picture of the BLDC and it controller please.
And post some spec/data on both.
Thanks.. Tom... 
Sorry tom i am supposed to say at this moment. After controlling perfectly, hope we may upload it officially
Nihaludeen:
How to control the speed of bldc motor without reducing voltage. I can able to control the speed by reducing the voltage( pwm signal ). But is it possible to control speed by varying frequency by making voltage as constant.
If you have a controller already controlling the motor speed, then it is varying the frequency to the motor in response to your PWM input.
You PWM input is not being directly applied to the BLDC.
This might help.
Tom...