timing electromotoren
Geplaatst: 14 aug 2016, 22:23
Hi
The timing depends on motor L, motor R, the number of poles and the operating point of motor (commution frequency, current).
The timing of a dc-motor can be compared with a combustion engine. The ignition angle is mainly a function of
engine speed. More speed means a more advanced ignition angle. That is due to the speed of the blast wave (constant speed assumed)
of combustion. Goal is to have a maximum of the blast wave at the top dead center of the piston. Thus more engine speed, more
advanced ignition is needed.
The same assumption is valid for the timing on dc-motors. To generated the max torque of a dc-motor,the magnetic field generated
by the motor windings must be orthogonal to the magnetic field of the permanent magnets.
The rise time of motor current is a function of L/R and actual motor current.
The commution frequency is a function of motor shaft speed * number of poles.
Outrunners have usually 14 poles, inrunners usually 2 or 4 poles. Thus the commutation frequency of an
outrunner is in most cases higher than compared to an inrunner.
The L of outrunners is due to more turns higher, also R. Current rise time at outrunners is normally lower.
Thus in general an outrunner need a more advanced timing compared to an inrunner.
I have done a few measurements concerning timing of inrunners/outrunners with a jeti spin 44 ESC and the jeti spin box.
The spin box shows engine rpm, current and accu voltage. A thumb rule for timing based on my measurements is:
* 2 poles motors: 0 - 5°
* 4 poles motors: 5 - 10°
* more than 10 poles: 15 - 20°
The timing depends on motor L, motor R, the number of poles and the operating point of motor (commution frequency, current).
The timing of a dc-motor can be compared with a combustion engine. The ignition angle is mainly a function of
engine speed. More speed means a more advanced ignition angle. That is due to the speed of the blast wave (constant speed assumed)
of combustion. Goal is to have a maximum of the blast wave at the top dead center of the piston. Thus more engine speed, more
advanced ignition is needed.
The same assumption is valid for the timing on dc-motors. To generated the max torque of a dc-motor,the magnetic field generated
by the motor windings must be orthogonal to the magnetic field of the permanent magnets.
The rise time of motor current is a function of L/R and actual motor current.
The commution frequency is a function of motor shaft speed * number of poles.
Outrunners have usually 14 poles, inrunners usually 2 or 4 poles. Thus the commutation frequency of an
outrunner is in most cases higher than compared to an inrunner.
The L of outrunners is due to more turns higher, also R. Current rise time at outrunners is normally lower.
Thus in general an outrunner need a more advanced timing compared to an inrunner.
I have done a few measurements concerning timing of inrunners/outrunners with a jeti spin 44 ESC and the jeti spin box.
The spin box shows engine rpm, current and accu voltage. A thumb rule for timing based on my measurements is:
* 2 poles motors: 0 - 5°
* 4 poles motors: 5 - 10°
* more than 10 poles: 15 - 20°