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Wang Zhinan 1 Zhao Bo 2
[align=center](1. Liaoning Branch of China Ryukyu Engineering Company, Fushun, Liaoning 113006, China)
(2. Ankerui Electric Co., Ltd., Shanghai 201801) [/align] [p] Summary
Introduce the commonly used anti-sweeping electricity measures, and focus on the use of motor protection to achieve anti-sweeping electricity.
Key words
ARD; Motor Protector; Anti-Shock; JB/T 10736
[b]0 Introduction
[/b] "Xiangdian" refers to the grid voltage short-term voltage loss caused by lightning, short-circuit to the ground, reclosing, equipment start, power plant failure and other reasons, the short-term grid voltage fluctuations, short-term fault Electric power quality events such as seconds. Chemical companies have high requirements on the reliability of power supply to the system. Once the power supply system is shaken, it will cause protection device undervoltage protection and unexpected shutdown of the production equipment, which will cause the production line to collapse and accidents to expand, resulting in very large economic losses and even operations. The security of personnel poses a threat.
1 commonly used anti-shock measures
1.1 UPS anti-swing system
The operating power of the DCS, PLC and other control systems is accessed by the UPS power supply to achieve anti-sweep power. The working principle of the online UPS is shown in Fig. 1. When the power grid works normally, it supplies power to the load and charges the energy storage battery. When the utility power is under voltage or suddenly loses power, the UPS power supply starts to work, and the energy storage battery supplies power to the load. . [/p]
[p] When the system shakes, the coil of the contactor works normally by UPS power supply to keep the main contacts and prevent the motor from shutting down. When the bus loses power for more than a certain period of time, it is set according to the secondary control. The output is disconnected for a fixed time to avoid accidents after voltage recovery. The control wiring diagram is shown in Figure 2. [/p]
[p]1.2 DC-BANK Anti-Swing System
Inverter anti-swing power has the following methods:
(1) Cancel the inverter low-voltage protection setting and set quick restart. The disadvantage of this method is that the stopping and restarting of the key motor will affect the continuity of production and increase the number of defective products. In addition, the low voltage will often show the overcurrent protection of the inverter, and canceling the overcurrent protection will increase the risk of damage to the inverter itself. This method is rarely used by petrochemical companies that require higher levels of continuous production.
(2) DC-BANK system, mainly used in variable frequency motor and PLC/DCS power supply system. When the power grid is normal, the frequency converter is powered by the AC bus and the DC-BANK system is in a hot standby state. When the power grid is switched off or is switched from standby to automatic, the grid voltage is reduced and converted into DC bus power from the DC-BANK to the inverter. The inverter maintains normal work. Its operating mode is shown in Figure 3. A single control logic diagram is shown in Figure 4. [/p]
[p]1.3 Anti-Shocking Measures for Motors
AC contactors are widely used in low-voltage motor control systems. The common motor control circuit is shown in Figure 5, and the contactor is disconnected after the flashing occurs, causing the motor to stop rotating. [/p]
Motor anti-sway electrical contactor anti-sway electrical, anti-sway electrical contactor method:
(1) Using an anti-slopping electrical contactor (with a delay release/contactor that avoids the bouncing zone), the contactor does not immediately release when the shaky charge occurs, nor does it work in the critical jump zone. The installation wiring is shown in Figure 6. .
(2) Add a delay module to the original AC contactor. The control circuit is shown in Figure 7.
(3) Install the restart controller and start the control circuit as shown in Figure 8.
[p] (4) Use a motor protector with anti-swing function. The motor protector has protection functions such as overload, phase failure, unbalance, locked rotor, blocking, start-up timeout, over-voltage, under-voltage, grounding, leakage, etc.; it has current measurement, voltage measurement, frequency measurement, power measurement and other measurement functions; Start control, anti-sweep power function, loss of pressure and other control functions; with 4-20mA DC transmission output, MODBUS, PROFIBUS communication. The Acry ARD series motor protector anti-swing control circuit (protection mode) is shown in Figure 9. [/p]
The working principle is as follows: 95-96 contacts are used as protective contacts. After the protector is powered on, it is normally closed. When a fault occurs or auxiliary power is turned off, it becomes normally open. 7-8 contacts are connected in parallel with the start button SB2. After the 7-8 pull-in control circuit is maintained in the starting state, the voltage can be executed immediately after the restart function.
The principle of anti-slopping power control using direct start method is shown in Figure 10. The 95-96 contact function is the same as Figure 9, and the 7-8 contact is the start control relay. After the protector receives SB1, it sends the jog start signal, and the 7-8 suction Combined self-holding, the contactor KM coil is electrically connected to the motor main circuit; after the protector receives SB2 sends a jog stop signal, the 7-8 output is disconnected, the contactor KM coil is de-energized, and the motor main circuit is disconnected; After power, the coil KM loses power, the motor main circuit is cut off, and the protector automatically selects “immediate restart”, “delayed delay self-start” or “disable start” according to the length of the shakiness.
[p] The function description of the motor protector industry standard (JB/T 10736) against jitter (reduced voltage reset) function: "The protector with undervoltage (voltage loss) restart protection function, due to the main circuit undervoltage fault In case of a loss of pressure, if the voltage is restored to normal (allowing a restart setting above) during the “immediate restart time”, the protector can immediately return the motor to the operating state before the motor is stopped (without the start delay, Step-down and other processes); If the "immediate restart voltage loss time" is exceeded and the voltage is restored to the undervoltage (loss of voltage) restart setting value within the "delay restart delay time" setting time, the motor Delay start by "delay delay time of restart" (same process as normal start), the allowable error of delay time is ±10%; if the voltage recovers after "delay delay restart delay time", the motor will not Automatic restart, the error of recovery voltage value is no more than ±10%."
[b]2 Anti-Shock Operation of Motor Protector and Setting of Related Parameters
[/b] Take the Ankerui ARD series motor protection as an example. In order to achieve the anti-swing function, the motor protector must be equipped with an anti-swing module. Connect the AC input to the input of the anti-slopping module and the output of the anti-slosh module to the auxiliary input of the motor protector. Motor protection The voltage measurement signal of the device is taken from the upper level of the contactor to prevent the contactor from being disconnected when the power is shaken, and the recovery voltage cannot be measured. When the line is normally powered, the internal energy storage device of the anti-sweeping electrical module is in an energy storage state, and the electrical energy storage device of the anti-slopping electrical module supplies power to the motor protector during the electrical shaking to maintain the normal operation of the motor protector. After the system voltage recovers to the "restart voltage", the motor protector judges the duration of the flashing, and the time is less than "immediately restart the power-off time" and immediately pulls "the output relay 7-8 starter motor; the power swing time is longer than “Immediately restart the power-off time”, but less than the “allowed power-off time”, execute the delayed restart. The power-on time is longer than the “allowed power-off time” and no start is performed.
The motor protector can realize the immediate restart of Akira Electric, the restart of the voltage loss delay, and the long delay of the loss of pressure and the full protection function of overload, phase failure, blocking, blocking, overvoltage, and underpower. To ensure smooth operation of the motor and reduce system investment, it is of practical significance to use in the chemical industry. The settings of the relevant parameters are shown in Table 1. [/p]
[p]3 Conclusion
Several common methods of electrical shakiness treatment are introduced, and the method of anti-shudging of the motor protector is highlighted.
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Article Source: "Automation Application" 2014 No. 6

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