Protech ZOOM 425 ccpm Specifications download pdf (Page 198)

b. Keep the motor cool by using a heatsink

There are many different heatsinks available which fit R/C helicopter motors.

See Section 30.2.2.5, “Cooling options” for more info.

c. Use the correct switching frequency

Brushless coreless motors require a high switching frequency to run efficiently and avoid

overheating. Some motors require an extremely high switching frequency to avoid over-

heating. For example, the Kontronik Tango documentation states that a brushless ESC

with a switching frequency of 32 khz or more is required for this motor.

30.1.12.3. Coreless motors

A brushed or brushless motor can be either a cored or coreless motor.

A coreless motor has no iron core for its motor windings. Therefore the windings are over-

lapped in a tubular fashion and looks like a woven basket. This woven basket of windings can

either be layered around the inside of the motor case for a brushless motor, or wrapped

around the motor shaft for a brushed motor.

This type of motor can usually be recognized by spinning the motor shaft while the motor wires

are disconnected. A coreless motor will allow the rotor to turn freely because there is no iron

core to attract the magnets and therefore has no preferred angular rest position.

Coreless motors have several advantages which are relevant to R/C helicopters:

a. Size/weight

Coreless motors can be made smaller and lighter than motors with iron cores of the same

size.

b. Efficiency

Coreless motors have no eddy current losses, although this can be minimized on a cored

motor by using very thin laminations from exotic materials (such as Magnesil).

c. Lower Io

Because a coreless motor has no cogging (torque losses), the no-load current is much

lower. Some iron core motors eliminate cogging using a skewed armature, but this is com-

plicated.

30.1.12.4. Iron core rotor motors

A motor with an iron core for its windings can usually be recognized by spinning the motor

shaft. An iron core motor will exhibit a cogging effect where the motor rotation feels "rough" be-

cause the shaft will have certain preferred rest positions. Not all iron core motors will have a

cogging effect because this effect can be minimized or eliminated by staggering the rotor.

Cored motors have two main advantages:

a. Thermal stability

Technical Appendix

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Protech ZOOM 425 ccpm Specifications Page 198