brushless esc theory of operation
04-08-2007, 11:52 PM
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brushless esc theory of operation
are there any et's that can give me a detailed theory of operations on a brushless esc, do they look at the counter emf, phase shift,very the freq an voltage.
My esc never gives me a consistant power to the motor it varies from flight to flight I can never get full power out of my nippy black 1812 on an apc 10/4.7 prop
It will not even make the batt warm an does not give me the thrust I need
the batt is a 1800 8c an the esc is a 18 amp from art tech
I would love to know the theory behind esc as I am a et an worked in rf for yrs
My esc never gives me a consistant power to the motor it varies from flight to flight I can never get full power out of my nippy black 1812 on an apc 10/4.7 prop
It will not even make the batt warm an does not give me the thrust I need
the batt is a 1800 8c an the esc is a 18 amp from art tech
I would love to know the theory behind esc as I am a et an worked in rf for yrs
04-09-2007, 12:07 PM
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RE: brushless esc theory of operation
Hi Kerwin,
A brushless DC motor operates on the same principles as a permanant magnet brushed DC motor, but the mechanical brushes/commutator are replaced by electronic commutation, with in the case of sensorless controllers the timming of the commutation being provided by back emf from the motor. The speed of a brushless motor and brushed motors is determined by the voltage applied to the motor (Kv), PWM is used in both cases as the throttle control, though brushed motors usually use a lower PWM freq.
Our brushless motors can only be operated as AC motors in a practical manner using a variable frequency drive, it then is technically an AC synchronous motor and and must always be in perfect synch with the AC current, any load that exceeds the torque of the motor will result in a stall that requires a restart sequence at low frequency and low voltage. VFDs are complex, expensive and not comming to a flying field in the forseeable future, as the operating characteristics of this mode of operation is not suited to our propulsion needs.
While somewhat similar to AC synchronous motors, our PM variety are absolutley incompatible with normal fixed freq. AC (50-60Hz) a functional AC synchronous motor designed for for operation on fixed freq. AC requirers an induction or hysteresis element to provide starting torque from zero RPM, a PM motor in an AC environment has no torque at zero RPM, though it will run if you spin it with an external power source to get it close enough to synch speed.
Regards,
Pete
A brushless DC motor operates on the same principles as a permanant magnet brushed DC motor, but the mechanical brushes/commutator are replaced by electronic commutation, with in the case of sensorless controllers the timming of the commutation being provided by back emf from the motor. The speed of a brushless motor and brushed motors is determined by the voltage applied to the motor (Kv), PWM is used in both cases as the throttle control, though brushed motors usually use a lower PWM freq.
Our brushless motors can only be operated as AC motors in a practical manner using a variable frequency drive, it then is technically an AC synchronous motor and and must always be in perfect synch with the AC current, any load that exceeds the torque of the motor will result in a stall that requires a restart sequence at low frequency and low voltage. VFDs are complex, expensive and not comming to a flying field in the forseeable future, as the operating characteristics of this mode of operation is not suited to our propulsion needs.
While somewhat similar to AC synchronous motors, our PM variety are absolutley incompatible with normal fixed freq. AC (50-60Hz) a functional AC synchronous motor designed for for operation on fixed freq. AC requirers an induction or hysteresis element to provide starting torque from zero RPM, a PM motor in an AC environment has no torque at zero RPM, though it will run if you spin it with an external power source to get it close enough to synch speed.
Regards,
Pete
