Operational Instructions; When The Power Sw Is On; When The Power Sw Is Off; Operation Of The Pedal - Brother MD-602 Service Manual

16. Operational instructions

16.1 When the power SW is ON

• The motor power is created with the rectifying circuit and smoothing capacitor on the power PCB. To suppress the rush
current, the smoothing capacitor is charged through the resistor. After charging, the relay contact closes and the smooth-
ing capacitor is directly connected to the rectifying circuit.
• The solenoid power is 40VDC. This is created by rectifying and smoothing the 30VAC from the power transformer using
the control PCB.
• For the control power, +5V and +8V stabilized power is created on the control PCB. The stabilized power is a dropper
type.
• When the power is turned ON, connection of the operation panel and material edge sensor is checked. If these are not
connected, the tacking function on the control box is validated.
• When the power is turned ON, connection of the synchronizer is checked. If the synchronizer is not connected, opera-
tion in the manner of a clutch motor will take place. As performance as a servomotor is not attained, this is not recom-
mended unless the synchronizer is faulty.

16.2 When the power SW is OFF

• This motor has no special processes when the power is OFF.
• It takes approximately five minutes for the motor power's smoothing capacitor to discharge after the power is turned
OFF. Make sure that the LED (red) on the PCB is OFF before starting maintenance of the power PCB.

16.3 Operation of the pedal

• The treadle unit outputs an analog voltage according to the pedal position. The control unit reads this voltage and
converts it into a motor command.
• If it is not detected that the pedal is at the neutral position when the power is turned ON, the motor will not start. The
neutral position is the treadle unit output 1.5V±0.4V.

16.4 While running

• The motor is controlled by controlling the 3-phase inverter's output frequency and output voltage.
[ P t ] (power transistor error): Error when an error signal is received from the power PCB output element.
• The sewing machine pulley's rotation speed is detected by the sewing machine head's synchronizer. Feedback is con-
trolled to reach the commanded speed.
[ L o ] (lock): Error that occurs if the synchronizer signal is not detected for three seconds.
[ P U ] (pulley error): Error that occurs if the sewing machine rotation exceeds the maximum speed setting. (The pulley
setting is incorrect.)
• The motor drive power voltage is constantly checked, and the required control is executed. The following voltages are
detected.
[ O u ] (overvoltage): Error that occurs when 304VAC is exceeded.
[ O L ] (overload): Error that occurs when a level 290VAC or more continues for 160ms.
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