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4-2. Electronic Control and Its Functions
(1) Control circuit (block diagram)
Fig. 24
Fig. 25
(2) Functions
1 Phase control circuit
As illustrated in Fig. 25, the phase control element (triac) functions to increase or decrease the time (T) of
the line voltage waveform in order to control the amount of voltage applied to the motor.
2 Rotation speed detector
The rotation speed detector detects and monitors the rotation speed of the armature by means of a
magnetic sensor (magnet pick-up), incorporated in the controller, which detects flux changes generated by a
magnet mounted at the end of the armature shaft.
Waveform of voltage
applied to motor
t
Voltage
Line voltage
waveform (AC)
t
T
Time
When 't' becomes smaller, motor rotation
speed and torque decrease.
When 't' becomes larger, motor rotation
speed and torque increase.
When t = T, line voltage (full voltage) is applied.
t
t
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