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BrushLess DC motor question

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eeenginee

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Hi,

What type of output we will get in Field oriented control in motor control? How should the output currents and voltages should look like? How to know the amplitude of our voltage waveform by inputs?

thanks
 

In general the aim is to turn on coils when they get close to the magnets. Then magnetic attraction pulls the magnets toward the coils.
At closest approach you turn off the coils. Inertia causes the armature to continue rotating. (I suppose there are some drive circuits that turn on the coils with repulsive polarity, to get added torque or speed.)

The passing magnet is able to induce voltage in a coil. Some designs detect this signal and use it in the control circuitry.
 

What type of output we will get in Field oriented control in motor control?

Normally square wave from MOSFET bridge (Using PWM control signal )

How to know the amplitude of our voltage waveform by inputs?

Using hall sensor BLDC controller will detect the presents of permanent magnet close to the armature coil and power up that armature, so armature coil and permanent magnet will repel each other, due to several poles the system will get a rotational field and the motor start runn
 

What type of output we will get in Field oriented control in motor control?

Normally square wave from MOSFET bridge (Using PWM control signal )

Thank you for the answer. How can we measure these square wave forms and how to see them using instrument since they are internal in algorithm?

The output won't be sinusoidal? you told about the switching phases of sectors in space vector modulation. Please tell me the final output in FOC control?

thanks
 

Unless it's generating intentional harmonics, field oriented control will use sinusoidal waveforms. It can use hall sensors as position reference, but they won't directly control the phases as in simple BLDC control.
 

Unless it's generating intentional harmonics, field oriented control will use sinusoidal waveforms. It can use hall sensors as position reference, but they won't directly control the phases as in simple BLDC control.
Do you mean sinusoidal waveforms are sinusoidal phase current outputs? How does the 3 phase voltages wave form look like for 50microseconds pwm?
 

How does the 3 phase voltages wave form look like for 50microseconds pwm...

For small motors, you can use simple square wave pulses filtered with a simple capacitor. But if you want to extract any significant power out of the motor, it is wise to drive with sine waves (even 3-5-7 step synthesis is good). You will get smoother operation and greater power at the cost of more steps (extra complexity) in the program.
 

Stator rotating currents in BL DC motor

Hi,

how can the measured rotating Stator currents can be improved with compensated factor in vector Control bldc motor?

thanks
 

Re: Stator rotating currents in BL DC motor

measured rotating Stator currents can be improved with compensated factor...

Ideally, you can consider the stator current to be a vector that rotates at the same speed as the rotor. In other words, the stator is fed with a sinusoidal voltage with the same frequency as of the rotor (or a harmonic) - they should be phase locked during a steady state of rotation.
 

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