CN100483884C - High power motor over-voltage protection device - Google Patents

Abstract

A high-power motor overvoltage protection device, which includes three zinc oxide arresters, the negative poles of the three zinc oxide arresters are connected in parallel and connected to the ground terminal, and the positive electrodes of the three zinc oxide arresters are respectively connected to the three-phase power supply. Connected terminal connection, which is characterized by: there are also three sets of RC resistors connected in series with capacitors, one end of the three RC resistors is connected to the ground terminal, and the other end is connected to the three-phase electrical connection through a fuse. When in use, connect the ground terminal to the ground, and the three terminals used to connect with the three-phase electricity are respectively connected to the three connection lines between the vacuum switch and the motor or transformer. This high-power motor overvoltage protection device can effectively prevent overvoltage, the zinc oxide arrester will not operate frequently, and the damage rate of the high-power motor and transformer is reduced to 2%. The RC resistor and the zinc oxide arrester cooperate with each other to effectively protect the motor ,transformer.

Description

High-power motor overvoltage protection device

technical field

The invention relates to a high-power motor overvoltage protection device.

Background technique

With the development of the metallurgical industry, especially the development of iron and steel enterprises, the power of air compressors and electric furnaces is increasing, and the capacity of the corresponding motors and transformers that supply power to electric arc furnaces is increasing, generally reaching more than 6000kVA. Air compressors The motor of the electric arc furnace is frequently interrupted. The transformer that supplies power to the electric arc furnace is cut off 18-36 times a day without load. No-load current is easy to generate current-carrying overvoltage, which has been accumulated for many years. During the operation, the voltage affects the insulation of the motor and transformer, resulting in damage to the motor and electric arc furnace transformer. For example, the applicant had 6 electric arc furnace transformers in 1987. Due to the voltage The overvoltage electric arc furnace transformer was damaged 20 times, of which the winding and porcelain bottle were damaged 11 times, and the overvoltage damage rate reached 55%. Due to overvoltage, the cable connecting the transformer and the electric arc furnace also exploded many times. Eight motors were also damaged due to voltage overvoltage. In order to prevent the vacuum switch from cutting off the no-load current to generate overvoltage, a zinc oxide arrester is connected in parallel between the three-phase vacuum switch and the transformer as an overvoltage protection device for the electric arc furnace voltage. The zinc oxide arrester is a nonlinear element. Its resistance is very large, but when overvoltage occurs, the resistance value presented is very small. Although the current is released from the ground when the vacuum switch cuts off the no-load current to generate overvoltage, the power grid releases energy to the ground to protect the vacuum switch and the motor. 1. The transformer avoids overvoltage damage, but due to the frequent opening and closing of the vacuum switch, the zinc oxide arrester was frequently switched on and off before the modification. For a 4000kW electric arc furnace power supply equipment, the zinc oxide arrester was switched on and off 20 times a year, and the zinc oxide arrester was quickly fatigued. Damage, loss of protection for vacuum switches, motors and transformers, the damage rate of motors and transformers reaches 50%.

Contents of the invention

In order to overcome the above-mentioned shortcomings of the existing high-power motor voltage overvoltage protection device, the present invention provides a reliable high-power motor overvoltage protection device.

The high-power motor overvoltage protection device includes three zinc oxide arresters, the negative poles of the three zinc oxide arresters are connected in parallel and connected to the grounding terminal, and the positive electrodes of the three zinc oxide arresters are respectively connected to the terminal for three-phase electrical connection. Connection, which is characterized in that: there are also three sets of R-C resistance capacitors connected in series with resistors and capacitors, one end of the three R-C resistance capacitors is connected to the ground terminal, the other end is respectively connected to a fuse, and the three fuses are connected to each other. The other ends of the wires are respectively connected to the terminals used to connect with the three-phase electricity, and can also be connected to the positive poles of the three zinc oxide arresters. When in use, the grounding terminal of the high-power motor overvoltage protection device is grounded, and the three terminals used to connect with the three-phase electricity are respectively connected to the three connection lines of the vacuum switch and the motor or transformer.

The resistance value of the three R-C resistance capacitors of this high-power motor overvoltage protection device and the capacitance of the capacitor are different from the rated voltage of the input terminal. The relationship between the technical parameters of the resistor and capacitor and the rated voltage of the input terminal is shown in Table 1. :

Table 1

Rated voltage KV Rated capacitance μF±10% Rated resistance value Ω±10% 1min power frequency withstand voltage KV phase to phase and to ground 1.1Un/√3 Tanδ% 7.2 0.10 100 30 ≦10pcs ≦0.04 12 0.10 100 42 ≦10pcs ≦0.04 40.5 0.05 100 95 ≦10pcs ≦0.04

Model TYPE System rated voltage (effective value) kV Surge arrester rated voltage (effective value) kV Continuous operating voltage (effective value) kV DC 1mA reference voltage kV is not less than Nominal discharge current kV Steep slope impact residual pressure (peak value) 1/5us≤A 2ms square wave flow capacity is not less than A HY5WZ-17/45 10 17 13.6 twenty four 5 51.8 150 HY5WZ-10/27 6 10 8 14.4 5 31 150 HY5W-51/134 35 51 40.8 73.0 5 154 400

Table 2

See Table 2 for the relationship between the technical parameters of the arrester and the rated voltage at the input end.

The present invention is based on the principle of R-C resistance-capacitance absorption (using the AC impedance of the capacitor and the resistor in series to divide the voltage to obtain the required voltage), and using the grid parameters (impedance, current, voltage) to reasonably select the resistance value of the resistor R and the capacitor The capacitance of C, and calculate the overvoltage multiple value of the motor of the air compressor and the electric furnace transformer, the calculation result is an overvoltage of 1.66 times, and the electrical equipment considered for the insulation wiring voltage of 1.732 is within its insulation tolerance range. The R-C resistance-capacitance absorption device and the zinc oxide arrester both protect the motor and the transformer, but the working principles of the two are different. The R-C resistance-capacity protection is to change the circuit parameters (mainly impedance) to suppress the overvoltage or damage the overvoltage. voltage conditions. Zinc oxide surge arrester is a non-linear component. Its resistance value is large under normal voltage, but when overvoltage occurs, the resistance value is small, so that the power grid releases energy to the ground to protect electrical equipment from overvoltage damage. The present invention can effectively prevent overvoltage by selecting appropriate R—C resistance capacitor parameters, and the zinc oxide arrester will not operate frequently. With the refitted power supply equipment, the damage rate of high-power motors and transformers due to overvoltage is reduced to 2 %, R-C resistance capacitors and zinc oxide arresters cooperate with each other to effectively protect motors and transformers.

Description of drawings

Fig. 1 is a circuit diagram of the present invention.

Fig. 2 is a front view of the entity corresponding to Fig. 1 . -

FIG. 3 is a left side view corresponding to FIG. 2 .

Fig. 4 is a circuit diagram of the high-power motor overvoltage protection device, air switch and electric arc furnace transformer of the present invention.

FIG. 5 is a physical diagram corresponding to FIG. 4 .

Fig. 6 is a circuit diagram of the high-power motor overvoltage protection device, air switch and motor of the present invention.

FIG. 7 is a physical diagram corresponding to FIG. 6 .

In the above figure:

1. Conductor 2. Conductor 3. Mounting plate 4. Mounting plate 5. Conductor

6. Frame base 7. Wire 8. Wire 9. Wire

10. High-power motor overvoltage protection device 11. Wire 12. Wire 13. Wire

X1, X2, X3, XF1, XF2, XF3, XFR1, XFR2, XFR3, XF terminals

XQ3, XT3 terminal blocks FU1, FU2, FU3 fuses

R1, R2, R3 Resistor E Common Ground C1, C2, C3 Capacitor F1,

F2, F3 zinc oxide arrester Q1 air switch T three-phase transformer M motor

Detailed ways

The specific implementation of the high-power motor overvoltage protection device will be described in detail below in conjunction with the embodiments and accompanying drawings, but the specific implementation of the high-power motor overvoltage protection device is not limited to the following embodiments.

Embodiment one

The high-power motor overvoltage protection devices described in Fig. 1, Fig. 2 and Fig. 3 include zinc oxide arrester F1, zinc oxide arrester F2 and zinc oxide arrester F3. The negative poles of the three zinc oxide arresters are connected to the terminal XE for grounding. The zinc oxide arrester F1, the zinc oxide arrester F2, and the zinc oxide arrester F3 are connected with the terminal X1, the terminal X2, and the terminal X3 with wires such as the wire 9 for the positive electrode, and the feature is that there are also three-phase electric corresponding Three groups of resistors and capacitors in series R—C resistance capacitors, take R3—C3 resistance capacitors as an example to illustrate the connection of R—C resistance capacitors, the negative pole of capacitor C3 is connected to terminal XE, the positive pole of capacitor C3 is connected to the terminal XE of resistor R3 One end is connected, the other end of the resistor R3 is connected to one end of the fuse FU3 through the terminal XFR3, and the other end of the fuse FU3 is connected to the terminal X3 through the terminal XF3.

The rated voltage of the power supply in this embodiment is 7.2KV, the rated capacitances of capacitor C1, capacitor C2 and capacitor C3 are all 0.10μF±10%, and the rated resistance values of resistor R1, resistor R2 and resistor R3 are all 100Ω± 10%, the technical parameters of zinc oxide arrester F1, zinc oxide arrester F2, and zinc oxide arrester F3 are all in the third row in Table 2 (the system rated voltage is 6KV).

This embodiment is the configuration equipment for the power supply transformer T of the high-power electric arc furnace. The connection with the transformer T and the air switch Q1 is shown in Fig. 4 and Fig. 5 . Terminal X3 is respectively connected with the three output terminals of the air switch, for example, terminal X3 is connected with the output terminal XQ3 of the air switch Q1, and terminal X1, terminal X2, and terminal X3 are respectively connected with the three input terminals of the transformer T Connection, such as connection between terminal X3 and input terminal XT3 of transformer T. The rated capacity of the air switch is 800--2000A, and the rated capacity of the transformer T is 3000--6000KVA.

This embodiment can also be used as a configuration device for a high-power motor. The connection with the motor M and the air switch Q1 is shown in FIGS. Connect with the three output terminals of the air switch respectively, such as the terminal X3 and the output terminal XQ3 of the air switch Q1, and the terminal X1, the terminal X2, and the terminal X3 are respectively connected with the three input terminals of the motor M, For example, the terminal X3 is connected to the input end of the motor M. The rated capacity of the air switch is 800--2000A, and the rated capacity of the motor M is 2000--5000KW.

Embodiment two

The circuit diagram of this embodiment and the connection entity diagram of the corresponding electrical components are shown in Fig. 1 and Fig. 2. The rated voltage of power supply in this embodiment is 12KV, and the rated capacitance of capacitor C1, capacitor C2 and capacitor C3 are all 0.10μF±10%. , the rated resistance values of resistor R1, resistor R2 and resistor R3 are all 100Ω±10%, and the technical parameters of zinc oxide arrester F1, zinc oxide arrester F2, and zinc oxide arrester F3 are the second row in Table 2 ( System rated voltage is 10KV).

This embodiment can be used as a configuration device for a high-power electric arc furnace power supply transformer. The connection with the transformer T and the air switch Q1 is shown in Figure 4 and Figure 5. The rated capacity of the air switch is 800-1250A, and the rated capacity of the transformer T is 5500-6000KVA .

Present embodiment also can be used as the configuration equipment of high-power electric motor, sees Fig. 6 and Fig. 7 with the connection of electric motor M and air switch Q1, and the rated capacity of air switch is 800-1250A, and the rated capacity of electric motor M is 3000-5000KW.

Embodiment Three

The circuit diagram of this embodiment and the connection entity diagram of the corresponding electrical components are shown in Fig. 1 and Fig. 2. The rated voltage of the power supply in this embodiment is 40.5KV. The rated capacitance of capacitor C1, capacitor C2 and capacitor C3 is 0.05μF±10%. , the rated resistance values of resistor R1, resistor R2 and resistor R3 are all 100Ω±10%, and the technical parameters of zinc oxide arrester F1, zinc oxide arrester F2, and zinc oxide arrester F3 are the fourth line in Table 2 ( The rated voltage of the system is 35KV).

This embodiment can be used as a configuration device for a high-power electric arc furnace power supply transformer. The connection with the transformer T and the air switch Q1 is shown in Figure 4 and Figure 5. The rated capacity of the air switch is 1000-4000A, and the rated capacity of the transformer T is 40-150MVA . Present embodiment also can be used as the disposition equipment of high-power electric motor, sees Fig. 6 and Fig. 7 with the connection of electric motor M and air switch Q1, and the rated capacity of air switch is 300-800A, and the rated capacity of electric motor M is 3000-5000KW.

See Table 1 for other parameters of the above three embodiments.

Claims (1)

1. A high-power motor overvoltage protection device, which includes three zinc oxide arresters, the negative poles of the three zinc oxide arresters are connected in parallel and connected to the grounding terminal, and the positive electrodes of the three zinc oxide arresters are connected to the three The terminal connection of phase electrical connection is characterized in that: there are also three sets of R-C resistance capacitors connected in series with resistors and capacitors, one end of the three R-C resistance capacitors is connected to the ground terminal, and the other end is respectively connected to a fuse The other ends of the three fuses are respectively connected to the terminals used to connect with the three-phase electricity; when in use, the ground terminal is grounded, and the three terminals used to connect with the three-phase electricity are respectively connected to the vacuum switch and the motor or The three connection lines of the transformer; the relationship between the resistance value of the three R-C resistors, the capacitance of the capacitor and the rated voltage of the input terminal is when the rated voltage is 7.2KV or 12KV, the rated capacitance of the capacitor is 0.10μF±10% , the rated resistance of the resistor is 100Ω±10%; when the rated voltage is 40.5KV, the rated capacitance of the capacitor is 0.05μF±10%, and the rated resistance of the resistor is 100Ω±10%.

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