Fujitsu MHW2040AC Manual Do Utilizador

 

Hall-less three-phase twelve-pole motor is used for the spindle motor, and the 3-
phase full/half-wave analog current control circuit is used as the spindle motor 
driver (called SVC hereafter).  The firmware operates on the MPU manufactured 
by Fujitsu.  The spindle motor is controlled by sending several signals from the 
MPU to the SVC.  There are three modes for the spindle control; start mode, 
acceleration mode, and stable rotation mode. 

(1) Start mode 

When power is supplied, the spindle motor is started in the following sequence: 

a)  After the power is turned on, the MPU sends a signal to the SVC to charge the 

charge pump capacitor of the SVC.  The charged amount defines the current 
that flows in the spindle motor. 

b)  When the charge pump capacitor is charged enough, the MPU sets the SVC to 

the motor start mode.  Then, a current (approx. 0.3 A) flows into the spindle 
motor. 
It moves to c) or e) step depending on the condition of spindle motor.  It is 
treated as the stop condition, it moves to the step c).  Whereas, it is treated as 
the free-wheeling condition, it moves to the step e). 

c)  The phase of the current flowed in the motor is changed in the order of (V-

phase to U-phase),  (W-phase to U-phase), (W-phase to V-phase), (U-phase to 
V-phase), (U-phase to W-phase), and (V-phase to W-phase) (after that, 
repeating this order). 
The above operations mean the generation of rotational magnetic field. 

d)  During phase switching, the spindle motor starts rotating in low speed, and 

generates a back electromotive force.  The SVC detects this back 
electromotive force and reports to the MPU using a PHASE signal for speed 
detection. 

e)  The MPU is waiting for a PHASE signal.  When no phase signal is sent for a 

specific period, the MPU resets the SVC and starts from the beginning.  When 
a PHASE signal is sent, the SVC enters the acceleration mode. 

(2) Acceleration mode 

In this mode, the MPU stops the phase switching to the SVC.  The SVC starts a 
phase switching by itself based on the back electromotive force.  Then, rotation of 
the spindle motor accelerates.  The MPU calculates a rotational speed of the 
spindle motor based on the PHASE signal from the SVC, and waits till the 
rotational speed reaches 4,200 rpm.  When the rotational speed reaches 4,200 rpm, 
the SVC enters the stable rotation mode. 

(3)  Stable rotation mode 

The SVC builds the PLL circuit into, and to become the rotational speed of the 
target, controls a stable rotation with hardware.  

The firmware calculates time of one rotation from PHASE signal. PHASE signal is 
outputted from the SVC. And the firmware observes an abnormal rotation.

C141-E258 

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