Protech ZOOM 425 ccpm Spécifications télécharger pdf (Page 193)

Once the motor is running at 100 rpm, the brushless motor controller can rely on the back EMF

to sense the magnet position and can commutate the motor using strictly back EMF sensing.

In an R/C model helicopter, the motor has a high load because it is coupled to the main (and

possibly tail) rotor which is fairly heavy. So, with lower torque motors and high motor loads, the

motor may not start spinning when the ESC goes through the blind commutation stage. The

main symptom for this is the motor will wiggle back and forth instead of starting to spin.

30.1.10.3. Governor mode

A feature of an ESC which will try to keep the motor speed constant despite variable load

placed on the motor. This is like the cruise control on a car as it's going up and down hills.

Even though the load on the motor is variable as the car goes up and down hills, the cruise

control will try to maintain the same speed. The governor mode on an ESC will try to do

something similar. Even if the heli is performing wild maneuvers and the load on the main rotor

blade is highly variable, it will try to maintain a constant head speed.

If using a governor mode, the throttle curve should not be set to 100%. This is because the

governor mode needs a little bit of extra power so it can maintain headspeed. Using the cruise

control analogy, if you set the cruise control of a car to its maximum speed the cruise control

cannot maintain the maximum speed going up hills. Similarly, if you set the throttle to 100%

RPM then the governor mode will not be able to maintain it when the rotor is heavily loaded.

This is why the motor pinion should be selected so the desired headspeed can be achieved at

90 to 95% of the throttle - so the governor mode can work properly.

30.1.10.4. Timing Advance

The timing advance determines how early the ESC applies power to the electromagnets during

motor rotation. A higher timing advance will cause the electromagnets to be energized for a

longer period, which will increase the motor power but will also increase the current draw. This

is appropriate for aerobatic flight. A lower timing advance will cause the electromagnets to be

energized for a shorter period, which will decrease the motor power and will decrease the

power used. This is appropriate for duration flight.

30.1.10.5. For fixed pitch helicopters

You must select an ESC that can handle the current draw at full throttle, even if you do not

plan to fly the helicopter at full throttle.

For example, if a Corona hovers at half throttle and draws 14 amps, then the current draw from

the battery and ESC is NOT 14 amps. What actually happens is the battery and ESC are deliv-

ering 28 amps to the motor only 50% of the time.

Therefore, if you use a Phoenix 25 for the Corona, it will be overloaded even when hovering,

and will probably overheat and shut down when you apply more throttle.

Also, you want to select a motor that will hover your helicopter at no lower than 50% throttle for

this reason.

30.1.10.6. For collective pitch helicopters

If you select a motor with the proper Kv and the CP helicopter reaches 1600 rpm of headspeed

at 90% throttle and draws an average of 18 amps of current, then the ESC and battery are ac-

tually supplying 20 amps of current for 90% of the time.

If you select a motor with an excessively high Kv rating and the CP helicopter reaches 1600

Technical Appendix

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Protech ZOOM 425 ccpm Spécifications Page 193

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