The servo valve SV4-20 (15) 57-80/40-10-S451 is a core component in the turbine control system. It converts electrical signals into hydraulic signals and plays a crucial role in the start stop and load adjustment of the unit. It mainly consists of a torque motor, a two-stage hydraulic amplifier, and a mechanical feedback system.

A torque motor is a device that converts electrical signals into mechanical rotational torque. When an electrical signal is input by a servo amplifier, a current passes through the coil on the armature between the electromagnets in the torque motor, generating a magnetic field. Under the action of the magnets on both sides, a rotating torque is generated, causing the armature to rotate while driving the connected baffle to rotate.

The secondary hydraulic amplification system includes a dual nozzle and baffle system, as well as a spool valve system. Under normal and stable operating conditions, the distance between both sides of the baffle and the nozzle is equal. When there is an electrical signal input and the armature drives the baffle to rotate, the baffle moves closer to a nozzle, reducing the oil discharge area and flow rate of the nozzle, and increasing the oil pressure in front of the nozzle. The distance between the opposite nozzle and the baffle increases, resulting in an increase in oil leakage and a decrease in pressure in front of the nozzle. This converts the original electrical signal into a hydraulic signal.

The servo valves used in the DEH system of steam turbines mostly have the same working principle. They convert electrical signals into hydraulic signals through torque motors and hydraulic amplification systems, driving the spool valve of the hydraulic motor to move, changing the opening of the speed control valve, and adjusting the steam intake of the unit, so that the speed (or load) of the unit reaches the operator’s set value, and the system reaches a new equilibrium state. During the operation of the steam turbine, the servo valve SV4-20 (15) 57-80/40-10-S451 is of great significance for ensuring the stable operation of the unit.

Yoyik can offer other hydraulic pumps or valves for power plants as below:
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Van Servo (Servo Valve) Sm4-20(15)57-80/40-10-S182
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Mechanical Seal N.D.E L270
Main Sealing Oil Pump Bushing Kg70Kz/7.5F4
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Low-Plus Guided Wave Radar Liquid Level Transmitter 5301Ha-2S1V3Am00075Bana