Protech ZOOM 425 ccpm Spécifications télécharger pdf (Page 199)

The motor windings in a cored motor can dissipate heat much better because the iron

core acts as a heat sink. This characteristic is important for extended operation at high

power levels.

b. Smaller air gap.

The clearance between the rotor and iron core can be minimized which increases effi-

ciency.

30.2. Motor selection guide

There are many, many motors available, but only a few are suitable for each helicopter. This is

because the rpm/V or the Kv of the motor is very important due to the fixed gearing ratio of the

drive system.

There are ten main criteria to consider when choosing a motor:

30.2.1. Electrical characteristics

30.2.1.1. Motor Kv

For a definition see Kv .

For collective pitch helicopters, the motor Kv and pinion size must be carefully selected so the

throttle will be between 90% and 100% when running at the desired headspeed. See the Sec-

tion 30.1.10, “How ESCs work” section for more information.

For a fixed pitch helicopter, the motor cannot run at a constant speed so some inefficiency is

unavoidable. The motor Kv and pinion size should be selected so the hovering headspeed is

about 50% of the maximum headspeed possible. (The hovering headspeed for most wide-

blade fixed pitch helicopters is about 1200-1300 rpm.)

Given two motors which are identical except for the Kv, the motor with the higher Kv will be

more powerful and use more current, and the motor with the lower Kv will be weaker but use

less current.

30.2.1.2. Motor Io

For a definition see Io .

The motor's Io is one factor which will help you determine the motor's efficient operating range.

For example, an ECO Piccolo requires about 3 amps to hover with a Hacker B20-36S. This

motor has an Io of about 400 ma, so about 2.6 amps is used for hovering (minus other effi-

ciency losses).

A Mega 16/15/4 would fit in the ECO Piccolo frame, but its Io is 1.1 amps. Therefore, the

power usage would probably rise to 2.6 amps + 1.1 amps = 3.7 amps. About 30% of the hover-

ing current is consumed by Io, which is a very high value, so therefore this motor is not very ef-

ficient when used in the 3 amp range.

A good rule of thumb for micro is to allocate about 10-15% of the hovering current for the mo-

tor's Io. For nonmicros, the percentage should be lower - about 7-10% is usually reasonable.

Technical Appendix

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Protech ZOOM 425 ccpm Spécifications Page 199