Elmo HARSFEN0602, HARmonica software manual Commutation sensors, Rotor Magnetic field sensors

HARSFEN0602ElmoHARmonicaSoftwareManual			PRELIMINARYDRAFT
				105
	WS[20]	Stator field angle, in 1024 counts/rev units.
		Stator field angle (deg) = WS[20]	(360/1024)
	WS[21]	Commutation counter. WS[21] counts the main high-resolution position
		sensor, modulo CA[18].

9.3Commutation sensors

For BLDC commutation, rotor position sensors are required.× The commutation sensors divide into two main groups.

- Direct field sensors that sense the magnetic field of the motor. - Shaft position sensors.

9.3.1 Rotor Magnetic field sensors

The first group consists mainly of digital Hall sensors. (Analog Hall sensors are less common and the Harmonica doesn't know to use them). Digital Hall sensors may be used for commutation with minimum calculation, since they reflect the direction of the rotor with respect to the windings directly. The digital Hall sensors yield, however, only crude information. Standard digital Hall sensors divide the electrical period of motor to six – see Figure 6.

The reading of the digital Hall sensors is according to Table 9-1.

The BLDC field angle is the field angle that produces maximum torque for this Hall sensor reading.

Hall A	Hall B	Hall C	Electrical rotor	BLDC Field
			position (deg)	angle (deg)
0	0	0	Illegal
1	0	0	330-30	90
1	1	0	30-90	150
0	1	0	90-150	210
0	1	1	150-210	270
0	0	1	210-270	330
1	0	1	270-330	30
1	1	1	Illegal

Table 9-1: Hall sensor values