MC33035, NCV33035
http://onsemi.com
22
Sensor Phasing Comparison
There are four conventions used to establish the relative
phasing of the sensor signals in three phase motors. With six
step drive, an input signal change must occur every 60
electrical degrees; however, the relative signal phasing is
dependent upon the mechanical sensor placement. A
comparison of the conventions in electrical degrees is shown
in Figure 40. From the sensor phasing table in Figure 41,
note that the order of input codes for 60° phasing is the
reverse of 300°. This means the MC33035, when configured
for 60° sensor electrical phasing, will operate a motor with
either 60° or 300° sensor electrical phasing, but resulting in
opposite directions of rotation. The same is true for the part
when it is configured for 120° sensor electrical phasing; the
motor will operate equally, but will result in opposite
directions of rotation for 120° for 240° conventions.
Figure 40. Sensor Phasing Comparison
Rotor Electrical Position (Degrees)
300°
240°
720660600540480420360300240180120600
S
B
S
A
120°
60°
S
C
S
A
S
B
S
C
S
C
S
B
S
A
S
C
S
B
S
A
Sensor Electrical Phasing
Sensor Electrical Phasing (Degrees)
60° 120° 240° 300°
S
A
S
B
S
C
S
A
S
B
S
C
S
A
S
B
S
C
S
A
S
B
S
C
1 0 0 1 0 1 1 1 0 1 1 1
1 1 0 1 0 0 1 0 0 1 1 0
1 1 1 1 1 0 1 0 1 1 0 0
0 1 1 0 1 0 0 0 1 0 0 0
0 0 1 0 1 1 0 1 1 0 0 1
0 0 0 0 0 1 0 1 0 0 1 1
Figure 41. Sensor Phasing Table
In this data sheet, the rotor position is always given in
electrical degrees since the mechanical position is a function
of the number of rotating magnetic poles. The relationship
between the electrical and mechanical position is:
Electrical Degrees + Mechanical Degrees
ǒ
#Rotor Poles
2
Ǔ
An increase in the number of magnetic poles causes more
electrical revolutions for a given mechanical revolution.
General purpose three phase motors typically contain a four
pole rotor which yields two electrical revolutions for one
mechanical.
Two and Four Phase Motor Commutation
The MC33035 is also capable of providing a four step
output that can be used to drive two or four phase motors.
The truth table in Figure 42 shows that by connecting sensor
inputs S
B
and S
C
together, it is possible to truncate the
number of drive output states from six to four. The output
power switches are connected to B
T
, C
T
, B
B
, and C
B
.
Figure 43 shows a four phase, four step, full wave motor
control application. Power switch transistors Q
1
through Q
8
are Darlington type, each with an internal parasitic catch
diode. With four step drive, only two rotor position sensors
spaced at 90 electrical degrees are required. The
commutation waveforms are shown in Figure 44.
Figure 45 shows a four phase, four step, half wave motor
controller. It has the same features as the circuit in Figure 38,
except for the deletion of speed control and braking.
MC33035 (60°/120° Select Pin Open)
Inputs Outputs
Sensor Electrical
Spacing* = 90°
Top Drives Bottom Drives
S
A
S
B
F/R B
T
C
T
B
B
C
B
1
1
0
0
0
1
1
0
1
1
1
1
1
0
1
1
1
1
0
1
0
0
0
1
1
0
0
0
1
1
0
0
0
1
1
0
0
0
0
0
1
1
1
0
0
1
1
1
0
1
0
0
0
0
1
0
*With MC33035 sensor input S
B
connected to S
C
.
Figure 42. Two and Four Phase, Four Step,
Commutation Truth Table
