In waste heat power generation, low voltage drawer cabinet room voltage below 660V, current below 1000A control and cabinet electrical equipment. It is the middle link of automatic control, and it is an important link connecting DCS cabinet and field actuator. Its reliable operation is an important part of power plant to improve power generation and create high income. We need to understand its principle, operation method and matters needing attention during maintenance and operation.
1、 Drawer cabinet can be divided into feed cabinet and control cabinet according to its function
1. Feeder cabinet
Its main function is to supply the three-phase voltage of the low-voltage bus through the circuit breaker in the cabinet to the soft start cabinet of the inverter control cabinet, the station control panel and other electrical cabinets. The air switch of the drawer cabinet has a trip coil, which can protect the short-circuit protection of the transmission line and terminal equipment, and switch the fault power supply. It is connected in series with the current transformer and equipped with the current relay through the main circuit, When the short-circuit current is detected, the current relay with inverse time limit will act to drive the trip coil of the main circuit breaker in the cabinet and switch the fault power supply. The larger the short-circuit current is, the shorter the action time is. This is a major feature of inverse time limit protection. When the power supply current is small, the protection action of the circuit breaker itself can be relied on.
2. Control cabinet
Its main function is to implement the forward and reverse rotation of zipper machine, shut-off valve, condensate pump and other electrical equipment and the comprehensive protection of the motor on the drawer cabinet through the DCS control signal of the central control room through the combined control circuit of circuit breaker, contactor and relay equipment. When the motor is lack of phase or short circuit, the normally open contact of the protector will close and cut off the control circuit of the drawer cabinet, Control contactor short circuit, cut off the power supply. The control cabinet also has relay and control circuit, and the communication between central control computer and equipment is normal.
2、 Precautions for low voltage drawer cabinet
Drawer cabinet generally forbids the main circuit to be responsible for live propulsion and directly load, so low-voltage drawer cabinets are equipped with mechanical interlocking mechanism.
1. When pushing, first of all, it is necessary to aim at the guide rail and balance the pushing (the position switch of the control cabinet is in the off position and the locking small switch is in the in and out position).
2. Introduction to the position of locking small switch:
a. Operating position
b. Test location
c. In and out position
d. Maintenance position
3. When operating the drawer cabinet, it is necessary to check the position of the small locking switch, and do not operate blindly, so as not to cause equipment failure.