AN1362 STMicroelectronics, AN1362 Datasheet - Page 3

• Manufacturer Part Number: AN1362
• Description: SWITCHED RELUCTANCE MOTOR CONTROL BY ST FIVE
• Manufacturer: STMicroelectronics

Figure 3.
Generally, the introduction of the pre-phase current injection is achieved by adjusting the position sensor
of few mechanical degrees forwards or backwards with respect to the rotor rotation.
However, since sensors were permanently locked on the rotor in the motor being explained, the pre-phase
injection could be applied only through a fixed value of advance. In this case, the current values are suited
only for a specific speed range, in which the motor achieves the required efficiency.
For high speed values, the drawback of having fixed sensor configuration, as in the case of the motor
being explained, can be overcome by adopting the strategy of extracting information from the combination
of signals coming from Hall sensors to change run time the prephase value for the current injection.
This solution is enhanced further through a “current tail cut“ technique, which is described in the following.
These circumstances are in conflict with the research of techniques allowing the achievement of a very
high speed with a reasonable
encoder signal by changing the driving policy to “run time”. This method is up-graded by using a Timer to
switch off the phase signal.
Figure 4. SRM MOTOR: MECHANICAL CHARACTERISTICS
35mHr
35mHr
35mHr
10mHr
10mHr
10mHr
L22
L22
L22
L33
L33
L33
L11
L11
L11
SENSOR PLACEMENT AND DRIVING
15
15
15
60
60
60
90
90
90
105
105
105
One rotor turn
One rotor turn
One rotor turn
Start up sequence
150
150
150
torque.
Torque
Low speed, constant torque
E2
E2
E2
195
195
195
A sequence of different logical functions may modify the input
240
240
240
285
285
285
330
330
330
Normal working area
Counter-Clockwise
Counter-Clockwise
Counter-Clockwise
375
375
375
direction
direction
Pre-phase
Acceleration
Speed
Encoder #1
Encoder #1
Encoder #1
Encoder #2
Encoder #2
Encoder #2
Encoder #3
Encoder #3
Encoder #3
No Pre-phase Firing
No Pre-phase Firing
No Pre-phase Firing
G1=E1&E2
G1=E1&E2
G1=E1&E2
G2=E2&E3
G2=E2&E3
G2=E2&E3
G3=E3&E1
G3=E3&E1
G3=E3&E1
Pre-phase Firing:
Pre-phase Firing:
Pre-phase Firing:
G1=E1n&E2n
G1=E1n&E2n
G1=E1n&E2n
G2=E2n&E3n
G2=E2n&E3n
G2=E2n&E3n
G3=E3n&E1n
G3=E3n&E1n
G3=E3n&E1n
AN1362
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