1. Common anti-sloshing measures and applications (1) UPS anti-sloshing system control systems such as DCS, PLC and other working power supplies are connected by the UPS power supply to achieve the purpose of anti-sloshing. The working principle block diagram of the online UPS is shown in Figure 1. When the grid voltage is working normally, the load is powered and the energy storage battery is charged. When the mains is under voltage or suddenly loses power, the UPS power supply starts to work, and the load is supplied by the energy storage battery.
figure 1
When power sloshing occurs in the system, the coil of the contactor works normally by the UPS power supply, keeping the main contacts attracted to avoid the motor shutdown caused by power sloshing. When the bus is de-energized for more than a certain time, the output is disconnected according to the time set in the secondary control section to avoid accidents after the voltage is restored. The control wiring diagram is shown in Figure 2.
figure 2
(2) The DC-BANK anti-sloshing system has the following methods to deal with the anti-sloshing of the inverter:
Method 1: Cancel the low-voltage protection setting of the inverter and set a quick restart. The disadvantage is that the stop and restart of the key motor will affect the continuity of production and cause the increase of defective products. In addition, the low voltage will often appear as the overcurrent protection of the inverter. Canceling the overcurrent protection will increase the hidden danger of the inverter itself. This method is rarely used in petrochemical enterprises with high continuous production requirements.
Method 2: DC-BANK system, DC-BANK system is mainly used in frequency conversion motor and PLC / DCS power supply system. When the grid is normal, the inverter is powered by the AC bus, and the DC-BANK system is in the hot standby state. When the power grid is shaken or switched from automatic switching, the voltage of the power grid drops and it is converted to DC-BANK to supply power to the DC bus of the inverter. The inverter maintains normal operation. Its working mode is shown in Figure 3, and the single control logic diagram is shown in Figure 4. Show.
image 3
Figure 4
(3) Anti-sloshing measures for motors AC contactors are widely used in low-voltage motor control systems. The common motor control circuit is shown in Figure 5. After the sloshing occurs, the contactor is disconnected and the motor stops.
Figure 5
. The anti-sloshing of the motor is mainly the anti-sloshing of the contactor. The anti-sloshing method of the AC contactor:
Method 1: Use anti-sloshing electrical contactors. Contactors with a delayed release / avoiding bouncing zone are called anti-sloshing electrical contactors. The contactors are not released immediately when sloshing occurs, nor do they work in the critical bouncing zone. Control wiring installation wiring is shown in Figure 6.
Image 6
Method 2: Add a delay module to the original AC contactor, and its specific control circuit is shown in Figure 7.
Picture 7
Method 3: Install the restart controller. The start control circuit of the self-start controller with the restart module is shown in Figure 8.
Picture 8
Method 4: Use a motor protector with anti-sloshing function. The motor protector has protection functions such as overload, phase failure, unbalance, locked rotor, blocking, starting overtime, overvoltage, undervoltage, grounding, and leakage; with current Measurement, voltage measurement, frequency measurement, power measurement and other measurement functions; with start control, anti-shock function, loss of voltage and other control functions; with DC 4-20mA transmission output, MODBUS, PROFIBUS communication function, can improve production automation Degree, reduce equipment investment, anti-shake control circuit of Ankerui ARD series motor protector is shown in Figure 9.
Picture 9
The working principle of Figure 9 is as follows: "95, 96" contacts are used as protection contacts. The protector is normally closed after power-on, and becomes normally open when a fault occurs or the auxiliary power supply is powered off. The "7, 8" contact is connected in parallel with the start button SB2. After the electric shock occurs, the "7, 8" pull-in keeps the control loop in the starting state, and the restart function can be performed after the voltage is instantaneous. Fig. 9 is an example of the wiring of the anti-shake function of the protector using the protection mode, and Fig. 10 is a schematic diagram of the anti-shock control using the direct start method.
The working reasons of Figure 10 are as follows: The "95, 96" contacts are the same as the functional description in Figure 9. The "7, 8" contact is the start control relay. The protector receives the "SB1" to send a jog start signal. The "7, 8" attracts and self-holds. The KM coil of the contactor is electrically connected to the main circuit of the motor. The protector receives the "SB2" to send 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 the occurrence of power sloshing, the main circuit of the coil KM power failure motor is cut off, and the protector automatically chooses to execute "immediate restart", "delayed self-starting in batches" or "start prohibition" according to the length of the power sloshing time.
Picture 10
The motor protector industry standard (JB / T 10736) describes the requirements for anti-shock (loss of voltage restart) function: "The protector with under voltage (loss of voltage) restart protection function, due to the main circuit under voltage failure or loss of voltage Stop, if the voltage returns to normal within the "immediate restart time" (allowed to restart above the set value), the protector can immediately restore the motor to the operating state before the motor stopped (without starting delay, voltage reduction, etc.) Process); if the "immediate restart voltage loss time" is exceeded and within the time set in the "delayed restart delay time", the voltage recovers to the value above the undervoltage (loss of voltage) restart value, the motor Time-restart delay time "delay start (same process as normal start), the allowable error of the delay time is ± 10%; if the voltage is restored after the" delay restart delay time ", the motor will not automatically restart Start. The error of the recovery voltage value is not more than ± 10%. "
2 The working principle of anti-sloshing of the motor protector and the setting of related parameters Taking the Ankerui ARD series motor protection as an example, the working principle of the anti-sloshing function of the motor protector is introduced with reference to FIG. 10. In order to realize the anti-sloshing function, the motor protector needs to have an anti-sloshing module. Connect the AC input to the input end of the anti-sloshing module. The output of the anti-sloshing module is connected to the auxiliary power input of the motor protector. The voltage measurement signal of the sensor 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-sloshing module is in an energy storage state. During the shaking, the anti-sloshing module energy storage device supplies power to the motor protector to maintain the normal operation of the motor protector. When the system voltage returns to the "restart voltage", the motor protector judges the duration of the sloshing time, the time is less than the "immediate restart power loss time" immediately pulls in the "output relay 7, 8" to start the motor; the sloshing time is longer than "Immediate restart power loss time", and less than "Allowed power loss time", execute delayed restart; Shake time is longer than "Allowed power loss time", do not perform start.
The use of motor protectors can realize immediate restart after power surge, delayed restart after loss of voltage, and over-locking start after too long loss of voltage. It also has comprehensive protection functions such as overload, phase failure, locked rotor, blocking, overvoltage, and underpower. It can ensure the smooth operation of the motor and reduce the system investment. It has practical significance in the chemical industry. The setting of related parameters is shown in Table 1.
Table 1
About the Author:
Yu Jing, female, undergraduate, engineer of Wuhan Ankerui Electric Co., Ltd., the main research direction is intelligent power monitoring and power management system
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