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Solenoid Valve in Wind Turbine
The hydraulic system of the wind turbine is actually the driving mechanism of the braking system, which mainly carries out the start-stop task of wind turbine. It is usually composed of two pressure holding circuits: one is to supply impeller brake system with accumulator, the other is to supply yaw brake system with accumulator. The job of these two circuits is to keep the brake system of the wind turbine under certain pressure when the wind turbine is running normally. When the pressure measured by the pressure sensor is less than the set value of the system, the PLC will control the start of the hydraulic station motor to compensate for the loss of pressure, so that the pressure value is always above the set value.
The following will respectively analyze yaw brake system and impeller brake system, as well as the hydraulic system drive during wind turbine operation.
Impeller brake system
The pitch system is the main braking system of the wind energy conversion system.
It is designed to have an independent electric drive for each blade and a battery to ensure safety in case of failure. A mechanical brake is also mounted on the high-speed side of the drive chain. This mechanical braking system is the third braking system of the wind energy conversion system, but it is not designed to keep the wind energy conversion system from exceeding the allowable speed limit under any conditions when the first and second braking systems fail.
The basic function of the mechanical brake is to make the rotor stop completely when it is decelerated by the variable pitch system. Mechanical brakes are also used to slow down the wind energy conversion system as soon as possible during emergency shutdown. This mechanical brake is driven by hydraulic pressure.
Impeller brake system of hydraulic system is working as follows. During normal operation, the opening and closing of the brake make the solenoid valve powered on, and the rotor brake is released. In case of emergency, brake opening and brake closing make solenoid valves powered off, the accumulator pressure oil enters brake calipers through brake opening valves, and the rotor brakes.
The pressure sensor disconnects the signal when the brake oil chamber is below a certain pressure value. Pressure sensor 2 monitors the accumulator's charging condition. When the pressure value is less than the set value, PLC controls oil pump motor to start charging.
Yaw brake system
Yaw brake mechanism consists of 8 to 10 hydraulic control yaw brake discs. The yaw system has two pressures, which provide the damping at yaw and the braking force at yaw end.
When the yaw does not work, all brake pads are locked; when the cabin is semi-loosened to all brake discs of the fan, enough damping is set to keep the cabin yaw smoothly. At this time, the yaw brake is used as the damper. The yaw brake pads are released when the cable is automatically unmoored.
Driving of hydraulic system in fan operation
The hydraulic system is equipped with ball valves on one side of the brake, so that the screw piston can be used to brake the solenoid valves when hydraulic pressure cannot be applied.
When the start-up command is issued, the brake opens and the solenoid valve get power, and the brake calipers discharge oil to the fuel tank, so the brake is released. The runtime state is maintained during the pause.
When the stop command is issued, the brake opens and the solenoid valve loses power. The pressure oil from the accumulator and pressure relief valve can enter the brake cylinder through the brake opening solenoid valve to realize the braking when the machine stops.
When the emergency shutdown occurs, the brake opens and the solenoid valve loses power. The accumulator makes pressure oil through the brake opening solenoid valve enter the hydraulic cylinder of the brake caliper. The speed of brake hydraulic cylinder is controlled by throttle valve.
The following will respectively analyze yaw brake system and impeller brake system, as well as the hydraulic system drive during wind turbine operation.
Impeller brake system
The pitch system is the main braking system of the wind energy conversion system.
It is designed to have an independent electric drive for each blade and a battery to ensure safety in case of failure. A mechanical brake is also mounted on the high-speed side of the drive chain. This mechanical braking system is the third braking system of the wind energy conversion system, but it is not designed to keep the wind energy conversion system from exceeding the allowable speed limit under any conditions when the first and second braking systems fail.
The basic function of the mechanical brake is to make the rotor stop completely when it is decelerated by the variable pitch system. Mechanical brakes are also used to slow down the wind energy conversion system as soon as possible during emergency shutdown. This mechanical brake is driven by hydraulic pressure.
Impeller brake system of hydraulic system is working as follows. During normal operation, the opening and closing of the brake make the solenoid valve powered on, and the rotor brake is released. In case of emergency, brake opening and brake closing make solenoid valves powered off, the accumulator pressure oil enters brake calipers through brake opening valves, and the rotor brakes.
The pressure sensor disconnects the signal when the brake oil chamber is below a certain pressure value. Pressure sensor 2 monitors the accumulator's charging condition. When the pressure value is less than the set value, PLC controls oil pump motor to start charging.
Yaw brake system
Yaw brake mechanism consists of 8 to 10 hydraulic control yaw brake discs. The yaw system has two pressures, which provide the damping at yaw and the braking force at yaw end.
When the yaw does not work, all brake pads are locked; when the cabin is semi-loosened to all brake discs of the fan, enough damping is set to keep the cabin yaw smoothly. At this time, the yaw brake is used as the damper. The yaw brake pads are released when the cable is automatically unmoored.
Driving of hydraulic system in fan operation
The hydraulic system is equipped with ball valves on one side of the brake, so that the screw piston can be used to brake the solenoid valves when hydraulic pressure cannot be applied.
When the start-up command is issued, the brake opens and the solenoid valve get power, and the brake calipers discharge oil to the fuel tank, so the brake is released. The runtime state is maintained during the pause.
When the stop command is issued, the brake opens and the solenoid valve loses power. The pressure oil from the accumulator and pressure relief valve can enter the brake cylinder through the brake opening solenoid valve to realize the braking when the machine stops.
When the emergency shutdown occurs, the brake opens and the solenoid valve loses power. The accumulator makes pressure oil through the brake opening solenoid valve enter the hydraulic cylinder of the brake caliper. The speed of brake hydraulic cylinder is controlled by throttle valve.
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