Large-scale three-phase asynchronous motor starting control device

Abstract

The utility model relates to a large-scale three-phase asynchronous motor starting control device which comprises a coupling and an auxiliary motor. The large three-phase asynchronous motor is a double-output-shaft working motor, and a rear-end output shaft of the working motor is connected with a front-end output shaft of the auxiliary motor through a coupler; the coupler is a clutch type coupler; the working motor is connected to a working three-phase alternating current power supply sequentially through a thermal overload relay, a contactor, a first circuit breaker and an isolating switch which are connected in series; the auxiliary motor is connected to a three-phase alternating current power supply for starting through a soft start controller or a frequency converter and a second circuit breaker which are connected in series in sequence; starting and stopping of a working motor and an auxiliary motor are controlled through a control circuit, a starting button, a stopping button and a first intermediate relay in the control circuit are sequentially connected in series and then connected with a direct-current power source, and a second control switch, a normally-closed contact of a contactor and a second intermediate relay are sequentially connected in series and then connected with the direct-current power source. The normally open contact is connected in series with the third intermediate relay and then connected with the DC power supply.

Description

Technical Field

[0001] The utility model belongs to the technical field of three-phase asynchronous motor starting control, in particular to a large three-phase asynchronous motor starting control device. Background Art

[0002] The three-phase asynchronous motor is a device that converts electrical energy into mechanical energy and is widely used in industrial production. When the three-phase asynchronous motor is in normal operation, the slip rate S is very small, generally 0.01 to 0.05, and the equivalent resistance of the motor rotor to the stator side is Very large, thus limiting the current of the motor; at the moment of starting, the slip rate S of the three-phase asynchronous motor is 1, and the motor rotor is calculated to be the equivalent resistance of the stator side. The starting current of the motor is very large, far exceeding the rated current. For squirrel cage three-phase asynchronous motors, the national standard stipulates that the starting current is 4 to 7 times the rated current. Common starting methods include step-down starting and variable frequency starting.

[0003] For a large centrifugal air compressor, a high-voltage three-phase asynchronous motor is used to drive it, with a rated power of 1600 kilowatts and a rated voltage of 10 kilovolts. It starts with a light load and then loads when the motor reaches the rated speed. If direct starting is used, it will cause an impact on the power grid and even cause the upper switch to trip; if soft starting or frequency converter is used, the cost of high-voltage equipment is generally high. Therefore, it is necessary to design a control device that uses a small three-phase asynchronous motor to drive a large three-phase asynchronous motor to start, thereby limiting the starting current of the motor. Summary of the invention

[0004] The utility model provides a large three-phase asynchronous motor starting control device to solve the technical problems existing in the known technology, which can effectively reduce the cost of equipment starting and limit the motor starting current.

[0005] The utility model includes the following technical solutions: a large three-phase asynchronous motor starting control device, comprising a coupling and an auxiliary motor; the large three-phase asynchronous motor is a double-shaft working motor, the rear end shaft of the working motor and the front end shaft of the auxiliary motor are connected by a coupling; the coupling is a clutch coupling; the working motor is connected to a three-phase AC power supply for work through a series-connected thermal overload relay, a contactor, a first circuit breaker and an isolating switch in sequence; the auxiliary motor is connected to a starting three-phase AC power supply through a series-connected soft start controller or a frequency converter and a second circuit breaker in sequence; the start and stop of the working motor and the auxiliary motor are controlled by a control circuit, a start button, a stop button and a first intermediate relay in the control circuit are connected in series in sequence and then connected to a DC power supply, a second control switch, a normally closed contact of the contactor and the second intermediate relay are connected in series in sequence and then connected to a DC power supply, and a normally open contact is connected in series with a third intermediate relay and then connected to a DC power supply.

[0006] Furthermore, the auxiliary motor is a single-shaft motor.

[0007] Furthermore, the three-phase AC power supply for starting is a three-phase AC power with a rated voltage of 380V.

[0008] Furthermore, the DC power supply is 24V.

[0009] Furthermore, when the start button is pressed, the first intermediate relay is energized and self-locked, and at the same time the second control switch is closed, and then the second intermediate relay is energized and transmits the start signal of the auxiliary motor to the soft start controller or inverter, connecting the auxiliary motor to the three-phase AC power supply for starting.

[0010] Furthermore, the auxiliary motor is a three-phase asynchronous motor, and the rated speed of the auxiliary motor is less than or equal to the rated speed of the working motor.

[0011] Furthermore, when the speed of the working motor is greater than that of the auxiliary motor, the coupling is in a disengaged state, and its function is that the auxiliary motor can drive the working motor to rotate, while the working motor does not need to drive the auxiliary motor to rotate, that is, after the working motor drives the working equipment to operate, the auxiliary motor is in a stopped state.

[0012] Furthermore, when the soft start controller or frequency converter detects that the auxiliary motor speed reaches the rated value, the normally open contact closes, the third intermediate relay is energized and self-locked, and at the same time controls the contactor to close and connect the working motor to the working three-phase AC power supply.

[0013] Furthermore, after the contactor is energized, its normally closed contact is disconnected, causing the second intermediate relay to be de-energized and stop working, and at the same time, a stop signal is transmitted to the soft start controller or the frequency converter to disconnect the auxiliary motor from the three-phase AC power supply for starting.

[0014] Furthermore, a first control switch is connected in parallel at both ends of the start button, and a third control switch is connected in parallel at both ends of the normally open contact; the first control switch and the second control switch are both controlled by a first intermediate relay, and the third control switch is controlled by a third intermediate relay.

[0015] The utility model has the following advantages and positive effects:

[0016] 1. The utility model first uses a small motor to drive a large motor when the motor is in a no-load or light-load state. When the large motor reaches a certain speed or reaches the rated speed, the industrial frequency power supply of the large motor is connected. Since the slip rate is small at this time, the starting current of the motor can be effectively limited.

[0017] 2. If the working motor is a high-voltage asynchronous motor, the small motor used for auxiliary starting of the utility model only needs to use a low-voltage three-phase asynchronous motor with a rated voltage of 380 volts. Compared with high-voltage equipment, the cost of low-voltage equipment such as inverters and soft starters is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the motor installation of the utility model;

[0019] Figure 2 It is the main electrical wiring diagram of a large three-phase asynchronous motor;

[0020] Figure 3 This is the main electrical wiring diagram for assisting the starting of a three-phase asynchronous motor;

[0021] Figure 4 It is the electrical control principle diagram of the utility model;

[0022] In the figure, M1-working motor; M2-auxiliary motor; L-coupling; FR-thermal overload relay; KM-contactor; QF1-first circuit breaker; QF2-second circuit breaker; QS-isolating switch; VF-frequency converter;

[0023] AC1-three-phase AC power supply for working; AC2-three-phase AC power supply for starting; DC1-DC power supply; SB1-start button; SB2-stop button; SA1-first control switch; SA2-second control switch; SA3-third control switch; KA1-first intermediate relay; KA2-second intermediate relay; KA3-third intermediate relay; NO-normally open contact. DETAILED DESCRIPTION

[0024] In order to further disclose the content, features and effects of the invention of the utility model, the following examples are specifically cited and described in detail in conjunction with the accompanying drawings. In the description of the following embodiments, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing this patent and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this patent.

[0025] In the description of the following embodiments, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0026] Example: See attached Figure 1-4 A large three-phase asynchronous motor starting control device includes a coupling L and an auxiliary motor M2; the auxiliary motor M2 is a single-shaft motor. The large three-phase asynchronous motor is a double-shaft working motor M1, and the rear end shaft of the working motor M1 and the front end shaft of the auxiliary motor M2 are connected by a coupling L; the coupling L is a clutch coupling.

[0027] The working motor M1 is connected to the working three-phase AC power supply AC1 through the thermal overload relay FR, contactor KM, first circuit breaker QF1 and isolating switch QS in series; the auxiliary motor M2 is connected to the starting three-phase AC power supply AC2 through the soft start controller or frequency converter VF and the second circuit breaker QF2 in series; the starting three-phase AC power supply AC2 is a three-phase AC with a rated voltage of 380V.

[0028] The start and stop of the working motor M1 and the auxiliary motor M2 are controlled by the control circuit. The start button SB1, the stop button SB2 and the first intermediate relay KA1 in the control circuit are connected in series in sequence and connected to the DC power supply DC1. The second control switch SA2, the normally closed contact of the contactor KM and the second intermediate relay KA2 are connected in series in sequence and connected to the DC power supply DC1. The normally open contact NO is connected in series with the third intermediate relay KA3 and connected to the DC power supply DC1. The DC power supply DC1 is 24V. The first control switch SA1 is connected in parallel at both ends of the start button SB1. The first control switch SA1 and the second control switch SA2 are both controlled by the first intermediate relay KA1. The third control switch SA3 is connected in parallel at both ends of the normally open contact NO, and the third control switch SA3 is controlled by the third intermediate relay KA3.

[0029] When the start button SB1 is pressed, the first intermediate relay KA1 is powered on and self-locked, and the second control switch SA2 is closed, and then the second intermediate relay KA2 is powered on and transmits the start signal of the auxiliary motor M2 to the soft start controller or the frequency converter VF, and the auxiliary motor M2 is connected to the three-phase AC power supply for starting. The auxiliary motor M2 is a three-phase asynchronous motor, and the rated speed of the auxiliary motor M2 is less than or equal to the rated speed of the working motor M1.

[0030] When the speed of the working motor M1 is greater than that of the auxiliary motor M2, the coupling L is in a disengaged state, and its function is that the auxiliary motor M2 can drive the working motor M1 to rotate, while the working motor M1 does not need to drive the auxiliary motor M2 to rotate, that is, after the working motor M1 drives the working equipment to operate, the auxiliary motor M2 is in a stopped state.

[0031] When the soft start controller or the frequency converter VF detects that the speed of the auxiliary motor M2 reaches the rated value, the normally open contact NO is closed, the third intermediate relay KA3 is powered on and self-locked, and the contactor KM is controlled to be attracted to connect the working motor M1 to the working three-phase AC power supply AC1. After the contactor KM is attracted, its normally closed contact is disconnected to de-energize the second intermediate relay KA2 and stop working, and at the same time, the stop signal is transmitted to the soft start controller or the frequency converter VF to disconnect the auxiliary motor M2 from the starting three-phase AC power supply AC2.

[0032] Since a clutch coupling L is used between the working motor M1 and the auxiliary motor M2, when the auxiliary motor M2 is disconnected from the three-phase AC power supply AC2 for starting, it will not continue to rotate with the working motor M1, and the auxiliary motor M2 is in a stopped state during the normal operation of the entire system. When the working motor M1 is started normally, it is loaded according to the settings of the system program.

[0033] Working principle: When the working motor M1 is unloaded or lightly loaded, the auxiliary motor M2 is used to drive the working motor M1. When the working motor M1 reaches a certain speed or reaches the rated speed, the working three-phase AC power supply AC1 of the working motor M1 is connected. Since the slip rate is small at this time, the starting current of the motor can be effectively limited. If the working motor M1 is a high-voltage asynchronous motor, the auxiliary motor M2 only needs to use a low-voltage three-phase asynchronous motor with a rated voltage of 380 volts. Compared with high-voltage equipment, the cost of low-voltage equipment such as inverters and soft starters is lower.

[0034] Although the preferred embodiments of the utility model are described above, the utility model is not limited to the above specific embodiments, which are merely illustrative and not restrictive. Under the enlightenment of the utility model, ordinary technicians in this field can make many forms without departing from the purpose of the utility model and the scope of protection of the claims. All of these belong to the protection scope of the utility model.

Claims

1. A large three-phase asynchronous motor starting control device, characterized in that: It includes a coupling and an auxiliary motor; the large three-phase asynchronous motor is a double-shaft working motor, and the rear end shaft of the working motor and the front end shaft of the auxiliary motor are connected by a coupling; the coupling is a clutch coupling; the working motor is connected to a three-phase AC power supply for working through a thermal overload relay, a contactor, a first circuit breaker and an isolating switch connected in series in sequence; the auxiliary motor is connected to a three-phase AC power supply for starting through a soft start controller or a frequency converter and a second circuit breaker connected in series in sequence; the start and stop of the working motor and the auxiliary motor are controlled by a control circuit, and the start button, the stop button and the first intermediate relay in the control circuit are connected in series in sequence and then connected to a DC power supply, the second control switch, the normally closed contacts of the contactor are connected in series with the second intermediate relay in sequence and then connected to a DC power supply, and the normally open contacts are connected in series with the third intermediate relay and then connected to a DC power supply.

2. A large three-phase asynchronous motor starting control device according to claim 1, characterized in that: The auxiliary motor is a single-shaft motor.

3. A large three-phase asynchronous motor starting control device according to claim 1, characterized in that: The three-phase AC power supply for starting is a three-phase AC power with a rated voltage of 380V.

4. A large three-phase asynchronous motor starting control device according to claim 1, characterized in that: The DC power supply is 24V.

5. A large three-phase asynchronous motor starting control device according to claim 1, characterized in that: When the start button is pressed, the first intermediate relay is energized and self-locked, and the second control switch is closed at the same time. Then the second intermediate relay is energized and transmits the starting signal of the auxiliary motor to the soft start controller or inverter, connecting the auxiliary motor to the three-phase AC power supply for starting.

6. A large three-phase asynchronous motor starting control device according to claim 5, characterized in that: The auxiliary motor is a three-phase asynchronous motor, and the rated speed of the auxiliary motor is less than or equal to the rated speed of the working motor.

7. A large three-phase asynchronous motor starting control device according to claim 6, characterized in that: When the speed of the working motor is greater than that of the auxiliary motor, the coupling is in a disengaged state.

8. A large three-phase asynchronous motor starting control device according to claim 6, characterized in that: When the soft start controller or frequency converter detects that the auxiliary motor speed reaches the rated value, the normally open contact closes, the third intermediate relay is energized and self-locked, and at the same time controls the contactor to close and connect the working motor to the working three-phase AC power supply.

9. A large three-phase asynchronous motor starting control device according to claim 8, characterized in that: After the contactor is energized, its normally closed contact is disconnected, causing the second intermediate relay to be de-energized and stop working. At the same time, a stop signal is transmitted to the soft start controller or the frequency converter to disconnect the auxiliary motor from the three-phase AC power supply for starting.

10. A large three-phase asynchronous motor starting control device according to any one of claims 1 to 9, characterized in that: The first control switch is connected in parallel at both ends of the start button, and the third control switch is connected in parallel at both ends of the normally open contact; the first control switch and the second control switch are both controlled by the first intermediate relay, and the third control switch is controlled by the third intermediate relay.

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