the standby power side 1C normally closed contact close, 2c Coil live, draw on AC contactor contact point 2C, through 2C, the backup power supply to six frequency converters to complete the automatic switching function. The actual power interlock circuit is powered by two groups of main and standby power sources, each group is powered by six inverters. To ensure the safe and reliable operation of the boiler unit, the interlock signals of full stop and stop of the forced draft fan and boiler are introduced in the circuit. After the modification of the main steam pressure regulating system of the unit, the frequency conversion regulating system has the following advantages: (1) the frequency conversion regulating system has wide range, high sensitivity and linearity up to 0.99. (2) the electric control circuit is simple and reliable. (3) it has the functions of automatic protection against power loss, phase failure, over-voltage and over-current of motor. (4) high power factor, high efficiency, energy saving and power saving. (5) the motor only accepts the three-phase power supply with adjustable frequency and omits the mechanical transmission gear. (6) AC frequency converter based on microprocessor replaces mechanical speed regulation, reliable control, easy maintenance and high performance-price ratio. (7) the utility model can realize constant motor torque, constant power output, uniform powder feeding and stable combustion, and reduce the steady combustion and oil feeding of the boiler. (8) the double working power supply is standby to each other. When the working power supply on one side is out of voltage, power cut off or under voltage, the working power supply on the other side will be put into operation automatically. (9) equipped with communication interface, can be connected to the distributed control system network, become the basic control station of the distributed control system, clutch separation is not completely, that is, usually said when the clutch down shift sound. This failure often has the following two phenomena: When the car starts, will clutch pedal to the end still feel difficult to shift gear, although the shift lever into gear, but not relax the pedals, the car moves forward or engine flameout; Shifting is difficult or the transmission lever can not be put into gear, and the transmission makes a rattling sound. The main reason why the clutch is not completely separated is that the friction Torque is not completely eliminated. Start the engine, push the clutch pedal all the way to the bottom, release the hand brake, change gears test, if the shift is difficult or the shift lever can not be put into gear,