Motors Database

The motors database (MOTORS.EDB) characterizes motors and gearboxes.


MFR This is the manufacturer or reseller of the motor (up to 10 characters).

Description is a description of the selected motor (up to 20 characters). Many of the European motors and the Aveox motors have a numbering system that describes the length and diameter of the motor. Unfortunately this standard is far from universal.

Kv is a motor constant , expressed in RPM/Volt, that indicates how fast the motor would turn for a given voltage if there were no internal resistance. It is inversely proportional to Kt, the torque constant. Kv is usually measured by chucking the motor shaft in a drillpress (hold the motor!) with a DVM connected to the motor leads. Run the drillpress and measure the DC volts from the motor (generator). Divide the drillpress RPM by the measured voltage. This should be done with neutral timing.

Izero or Io is a motor constant (Izero), expressed in amps, that indicates the amount of current necessary to turn a motor without load, or how much current does not contribute to the output power. Io is easy to measure but it generally requires the motor to be at neutral timing. In fact, we say we have neutral timing when we adjust for minimum Io. This must be done quickly, since a motor gets surprisingly hot under these conditions.

Rm is a motor constant , expressed in milliohms, which characterizes the equivalent internal resistance of the motor. Rm is the most difficult motor constant to measure. You typically need to supply about 10 amps to the motor while keeping the motor shaft from turning while measuring motor voltage and current. You need an accurate DVM to measure the voltage and an Astro meter is fine for the current. A battery pack with a load (power resistor or headlight) could supply the current. The motor timing does not matter, but shaft position can vary the reading. We like to take several readings while slowly rotating the shaft.

GEAR RATIO is the number of revolutions the motor must make to rotate the prop one revolution. There is a gearbox efficiency number in the ecalc.ini file. You can change this by editing this file. ElectriCalc will not let you put unreasonable numbers here.

MM is the magnet material (or an ingredient with a neat name). F-ferrite, C-cobalt, N-neodymium, S-strontium, ?-unknown. This is informational only and is not used by the program.

is turns of wire on each pole of the motor. This is informational only and is not used by the program.

COMMENTS are allowed at the end of the line.

PTR is a somewhat bizarre alphanumeric pointer assigned to this data entry for reference by the PLANES database. There is a small chance that two entries will have the same pointer and thus "confuse" the program into selecting the wrong one. This can generally be fixed by making a slight change in the description.