Hitachi RAM-40QH5 Service Manual page 47

6. Rotor magnetic pole position detection circuit
Fig. 6-1 Rotor magnetic pole position detection circuit
When the DC brushless motor is rotated, it also operates as power generator, generating reverse electromotive
force according to number of rotations. This reverse electromotive force is voltage-divided by R503-R505 and
R604-R011, and appears as point voltage. IC3 compares and digitalizes point voltage with point voltage
A A B
(in which DC voltage (Vd) is voltage-divided by R501, R502 and R608), and inputs this to microcomputer as
position detection signals for points , and . Microcomputer switches inverter using optimum timing based
C D E
on position detection signals, in order to control the rotation of the brushless motor.
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