MGM 100120-3 Operating Manual Download Page 34

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HBC-series V7 LV+MV

Optimal and allowed motor sensor position

Next picture displayed correct relative position all phases voltage (back EMF) and sensors. Phase voltage, as well as sensor signals, is
offset by 120°. Optimal sensor position is such that sensor signal edge correspond with “zero crossing” moment (marking by red ring
on the phase voltage).

Controller can compensate these sensor’s differences from optimal position. However here are some limits. When is edge of the sen-
sor signal

before

zero crossing, maximal possible timing value is not limited. In case, this edge is

after

zero crossing point, value of

maximal possible timing is lower (30° minus this difference).
When you change rotation direction, sensor position is “swapped”, i.e. sensor signals which had edge before zero crossing point will be
after zero crossing point and vice versa

– with all limitation for limiting maximal possible value of the timing.

Therefore we recommend difference from optimal position of the sensors up to ±10°. In this case is available timing up to 15 – 20° for
both direction of the motor rotation

– this value is enough for most the motors.

When your sensors have higher differences from optimal position, controller eliminate this value, but maximal possible timing value is
decrease for some of rotation direction.
In case, your motor don´t need timing (timing is 0°), tolerances of the sensors position from optimal position can be higher (up to ± 25°),
controller eliminate these differences.

In case, differences of sensors position are more than 25

– 30° electric (include magnet dimension tolerances and its positions !!!), con-

troller cannot eliminate these differences and signalize error (sensors error, motor error).

Two poles motor have identical electric and mechanical revolution (360°). This is not valid for motors with more poles.
For example 4-pole

s motor have one electric revolution by 180°mechanical revolution (360/2=180). This means two electric revolution

/one mechanical revolution. Etc.
Therefore motors with more poles have higher demands on mechanical accuracy. Motor with 12 poles have one electric revolution on
60° mechanical degrees (360/6=60), therefore maximal mechanical tolerances for sensors position is ±10°/ 6 = ±1,67°!!! (max.). The
same criteria are valid for magnets.

inspection:

If you are uncertain about the location of sensors (or their output signals), you can easily check.

- The controller mode switch to sensorless
- Disconnect the the engine from mechanical load (propeller, gearbox, ...)
- Spin the engine at full throttle by controller
- Measure by oscilloscope (2 channel at least) both the phase voltages (successively A, B, C), while each corresponding sensor the

output. You get similar waveforms as shown above. Important is the position sensor output edges to the passage of zero..

30°

Electric

360°

½ phase
voltage

Optimal
position

Optimal position of the

Sensor output signal

Edge

½ phase
voltage

Optimal
position

½ phase
voltage