Local control loop of coal feeder

Abstract

According to a coal feeder local control loop, a relay in a control loop in a coal feeder local control cabinet does not have a self-holding function, so that a relay coil in the coal feeder local control cabinet loses power in the switching process, and finally the coal feeder trips. The circuit comprises a manual starting loop and a DCS starting loop, the manual starting loop and the DCS starting loop are connected in parallel, and a main circuit formed after the manual starting loop and the DCS starting loop are connected in parallel is connected in series to a branch circuit formed by connecting a coil of a second relay (K2) and a coil of a time-delay relay (KY1) in parallel; the DCS starting loop comprises a DCS starting normally-open switch and a DCS stopping normally-closed switch which are connected in series. The normally-open contact of the second relay (K2) and the normally-open contact of the time-delay relay (KY1) are connected to the two ends of the DCS starting normally-open switch in parallel to serve as self-holding contacts. The on-site control system is used for on-site control of the coal feeder.

Description

Technical Field

[0001] The utility model relates to an on-site control circuit of a coal feeder. Background Art

[0002] In a thermal power plant, the coal feeder delivers pulverized coal to the pulverizer, which is then ground and sent to the furnace for combustion. The coal feeder is a very important auxiliary machine for the boiler. When all coal feeders stop, the boiler will lose fuel and cause boiler MFT, resulting in unit shutdown. Therefore, whether the coal feeder can operate stably is very important to the safe and stable operation of the unit.

[0003] The original coal feeder control circuit is as follows Figure 1 As shown in the figure, there are two AC 220V power supplies in the design (the main power supply is provided by the power plant UPS, and the backup power supply is provided by the power plant security section). When the main power supply is abnormal, it can automatically switch to the backup power supply within 100ms according to the power quick-cut device. However, it is found in actual operation that when the power supply of the main control system of the coal feeder is abnormal and automatically switches to the backup power supply, the relay in the control circuit of the local control cabinet of the coal feeder has no self-holding function. Therefore, during the switching process, the relay coil in the local control cabinet of the coal feeder will lose power, which will eventually cause the coal feeder to trip. Utility Model Content

[0004] In view of the deficiencies in the prior art, the utility model provides an on-site control loop for a coal feeder, which solves the problems raised in the above-mentioned background technology.

[0005] In order to achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] A coal feeder local control circuit, comprising a manual start circuit and a DCS start circuit, wherein the manual start circuit and the DCS start circuit are connected in parallel, and a main circuit of the manual start circuit and the DCS start circuit connected in parallel is connected in series to a branch circuit formed by connecting a coil of a second relay and a coil of a time delay relay in parallel;

[0007] The DCS start circuit includes a DCS start normally open switch and a DCS stop normally closed switch connected in series, and the normally open contacts of the second relay and the normally open contacts of the delay relay are connected in parallel at both ends of the DCS start normally open switch as self-holding contacts.

[0008] The coal feeder local control circuit, the power supply after the normally closed contact of the second relay and the coil of the third relay are connected in series is taken from the control power supply quick-cut outlet.

[0009] The local control loop of the coal feeder and the operation feedback signal of the DCS are connected to the normally open contact of the time delay relay. Beneficial Effects

[0010] 1. The normally open contact of the time delay relay of the utility model is disconnected 1 second after power failure. When the two control power supplies of the coal feeder are in the switching process (the switching time is 100ms, which is much shorter than the time delay relay that can be disconnected 1 second after power failure), the normally open contacts of all energized relays in the control circuit of the coal feeder are quickly closed within 100ms after the power is disconnected during the power switching process, so as not to cause the coal feeder to trip.

[0011] 2. When the coal feeder of the utility model is in operation, the third relay is de-energized, and the normally open contact of the third relay that sends signals to the frequency converter, the calculator and the low voltage ride-through device is changed to a normally closed contact. During the power switching process of the coal feeder, the second relay will not lose power, and the normally closed contact of the second relay is always in the normally open state. Therefore, the signals sent by the frequency converter, the calculator and the low voltage ride-through device are not affected.

[0012] 3. The utility model avoids the occurrence of coal feeder tripping accidents during the switching of two power supplies in the local control cabinet of the coal feeder, reduces the malfunction rate of the coal feeder, and improves the reliability of equipment operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Attached Figure 1 This is the circuit diagram of the original coal feeder local control circuit;

[0014] Attached Figure 2 It is a circuit diagram of an on-site control loop of a coal feeder of the utility model. DETAILED DESCRIPTION

[0015] Reference Figure 2 A coal feeder local control circuit, which comprises a manual start circuit and a DCS start circuit, wherein the manual start circuit and the DCS start circuit are connected in parallel, and the main circuit of the manual start circuit and the DCS start circuit connected in parallel is connected in series to a branch circuit formed by connecting the coil of the second relay K2 and the coil of the delay relay KY1 in parallel;

[0016] The DCS start circuit includes a DCS start normally open switch and a DCS stop normally closed switch connected in series. The normally open contact of the second relay K2 and the normally open contact of the delay relay KY1 are connected in parallel at both ends of the DCS start normally open switch as self-holding contacts.

[0017] The coal feeder local control circuit, the power supply after the normally closed contact of the second relay and the coil of the third relay K3 are connected in series is taken from the control power supply quick-cut outlet.

[0018] The local control loop of the coal feeder and the operation feedback signal of the DCS are connected to the normally open contact of the delay relay KY1.

[0019] Add a delay relay KY1 in the coal feeder control circuit and set the delay time to 1S.

[0020] The line feedback is changed from the normally open contact of the original second relay to the normally open contact of the delay relay KY1.

[0021] The self-holding contacts are changed to two parallel connections, namely the normally open contact of the original second relay and the normally open contact of the delay relay KY1. Under the action of the delay relay (the normally open contact will not disconnect until 1 second after the relay loses power), when the two control power supplies of the coal feeder are in the switching process (the switching time is 100ms, which is much shorter than the time it takes for the delay relay to disconnect after 1 second after power failure), the normally open contacts of all energized relays in the coal feeder control circuit will quickly close within 100ms after the power switching process is disconnected, so as not to cause the coal feeder to trip.

[0022] The power of the third relay coil is changed to the normally closed contact of the self-holding second relay. The power of the normally closed contact of the second relay is directly taken from the outlet of the quick-cut device. The three pairs of normally open contacts of the third relay K3 that are respectively sent to the frequency converter, the calculator, and the low voltage ride-through are changed to normally closed contacts. When the coal feeder is running, the third relay K3 is de-energized. The third relay contact that sends signals to the frequency converter, the calculator, and the low voltage ride-through device is changed to a normally closed contact. During the power switching process of the coal feeder, the second relay will not lose power, and the normally closed contact of the second relay will always be in a normally open state. Therefore, the signals sent by the frequency converter, the calculator, and the low voltage ride-through device are not affected.

Claims

1. A coal feeder local control circuit, which comprises a manual start circuit and a DCS start circuit, wherein the manual start circuit and the DCS start circuit are connected in parallel, and is characterized in that: The main circuit of the manual start circuit and the DCS start circuit connected in parallel is connected in series to a branch circuit formed by the coil of the second relay and the coil of the time delay relay connected in parallel; The DCS start circuit includes a DCS start normally open switch and a DCS stop normally closed switch connected in series, and the normally open contact of the second relay and the normally open contact of the delay relay are connected in parallel at both ends of the DCS start normally open switch as self-holding contacts; The electricity of the third relay coil is connected to the normally closed contact of the second relay, and the electricity of the normally closed contact of the second relay is directly taken from the outlet of the quick-cut device.

2. The coal feeder local control circuit according to claim 1 is characterized in that: The operation feedback signal of the DCS is connected to the normally open contact of the time delay relay.

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