Single-phase motor starting device with protection function

Abstract

The utility model discloses a single-phase motor starting device with a protection function, and relates to the technical field of one-way motor starting. Comprising a control circuit used for controlling a main circuit switch of the single-phase motor, and further comprises an auxiliary contactor, a time relay and an auxiliary capacitor, and a group of normally open contacts of the auxiliary contactor are connected with a control coil of the time relay in series and then are parallel to the control circuit; the auxiliary capacitors are connected in series with the other group of normally open contacts of the auxiliary contactor and then are connected in parallel with the operation capacitor of the single-phase motor, and multiple groups of auxiliary capacitors are connected in parallel; a control coil of the auxiliary contactor is connected in series with a centrifugal switch of the single-phase motor; and a normally closed contact of the time relay is connected in series with the control circuit. According to the utility model, the problem that the winding coil is destroyed and cannot be started due to overlarge load or long-time starting when the motor is started can be solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of unidirectional motor starting, in particular to a single-phase motor starting device with a protection function. Background Art

[0002] If a motor with a centrifugal switch cannot be started in a short time, the winding coil is easily destroyed, mainly because the winding is overheated or the insulation performance is reduced. The overheating of the winding is often caused by excessive current flowing through the winding. Therefore, there are two main types of motor protection: current and temperature detection.

[0003] The existing protection for single-phase motor starting devices mainly focuses on temperature detection. A single overheat protection cannot solve the problem of not being able to respond to sudden changes in motor load in a timely manner when the motor load suddenly increases, which can easily cause the motor to start unsteadily or even fail to restart.

[0004] Therefore, a single-phase motor starting device with a protection function is needed to solve the above problems. Utility Model Content

[0005] The utility model aims to provide a single-phase motor starting device with a protection function, which is used to solve the problem that the winding coil is destroyed and cannot be started due to excessive load when the motor is started, and enables the motor to be restarted when the starting fails, thereby improving the flexibility of the motor starting device.

[0006] The specific technical solutions are as follows:

[0007] A single-phase motor starting device with a protection function comprises a control circuit for controlling a main line switch of the single-phase motor, and further comprises an auxiliary contactor, a time relay and an auxiliary capacitor. A group of normally open contacts of the auxiliary contactor are connected in series with a control coil of the time relay and in parallel with the control circuit; the auxiliary capacitor is connected in series with another group of normally open contacts of the auxiliary contactor and in parallel with a running capacitor of the single-phase motor, and a plurality of groups of the auxiliary capacitors are connected in parallel; the control coil of the auxiliary contactor is connected in series with a centrifugal switch of the single-phase motor; and the normally closed contacts of the time relay are connected in series with the control circuit.

[0008] Preferably, the control circuit is connected in series with a fuse.

[0009] Preferably, it also includes a thermal relay, the thermal element of which is arranged on the main circuit of the single-phase motor, the normally closed contact of the thermal relay is connected in series with the control circuit and in parallel with the control coil of the time relay.

[0010] Preferably, the control circuit includes a first normally closed switch, a second normally open switch and a main contactor. The second normally open switch is connected in parallel with a group of contacts of the main contactor and in series with the first normally closed switch and the control coil of the main contactor; the remaining contacts of the main contactor are connected in series with the main circuit of the single-phase motor.

[0011] Preferably, fuses are respectively provided on the main circuits of the single-phase motors.

[0012] Preferably, the control circuit, auxiliary contactor, time relay and auxiliary capacitor are all arranged in an electrical box and connected to the single-phase motor connector through wires.

[0013] Compared with the existing technology, the beneficial effects of the utility model are:

[0014] The single-phase motor starting device with protection function described in the utility model adds an auxiliary contactor and a plurality of auxiliary capacitors in parallel to the running capacitor, so that the motor can be restarted when the starting fails, thereby improving the flexibility of the motor starting device. By setting a thermal relay, the protection of the winding coil is further enhanced, and the smoothness and safety rate of the motor starting are improved. By setting a time relay, the centrifugal switch is forced to stop when it does not stop working after the set time, thereby avoiding the situation of long-term starting. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a circuit diagram in an embodiment of the utility model;

[0016] Figure 2 It is a flow chart of the utility model.

[0017] In the accompanying drawings, 10, 11-normally open contacts of auxiliary contactors, 20, 21-normally open contacts of main contactors, 30-auxiliary capacitor, 40-operating capacitor, 50-centrifugal switch, 60-normally closed contact of thermal relay. DETAILED DESCRIPTION

[0018] The following is a further detailed description of the embodiments of the invention in conjunction with the accompanying drawings to make the objectives, technical solutions and technical effects of the invention more clearly presented.

[0019] like Figure 1As shown, a single-phase motor starting device with a protection function is disclosed, which specifically includes a control circuit for controlling the main line switch of the single-phase motor, and also includes an auxiliary contactor, a time relay and an auxiliary capacitor 30. A group of normally open contacts of the auxiliary contactor are connected in series with the control coil of the time relay and in parallel with the control circuit; the auxiliary capacitor 30 is connected in series with another group of normally open contacts of the auxiliary contactor and in parallel with the running capacitor 40 of the single-phase motor, and the auxiliary capacitor 30 is connected in parallel in multiple groups; the control coil of the auxiliary contactor is connected in series with the centrifugal switch 50 of the single-phase motor; the normally closed contacts of the time relay are connected in series with the control circuit.

[0020] Here, the main circuit is a power supply circuit for starting a single-phase motor, including a live wire L and a neutral wire N. The single-phase motor is provided with a centrifugal switch 50 connected in parallel with the main coil, and a running capacitor 40 connected in series with the auxiliary coil and in parallel with the main winding of the single-phase motor.

[0021] Here, the normally open contacts 10 and 11 of the auxiliary contactor are the normally open contacts of the auxiliary contactor, and the contactor can usually have 4 groups of contacts. Similarly, the normally open contacts 20 and 21 of the main contactor are the normally open contacts of the main contactor.

[0022] In this embodiment, the control circuit, auxiliary contactor, time relay and auxiliary capacitor 30 are all arranged in the electrical box and connected to the single-phase motor connector through a wire. The control circuit includes a first normally closed switch Sb1, a second normally open switch Sb2 and a main contactor. The second normally open switch Sb2 is parallel to a group of contacts of the main contactor and is connected in series with the first normally closed switch and the control coil of the main contactor; the remaining contacts of the main contactor are connected in series with the main circuit of the single-phase motor. The control circuit is connected in series with a fuse FU. The first normally closed switch Sb1 is a closing switch, and the second normally open switch Sb2 is a starting switch.

[0023] The main circuit of the single-phase motor is provided with a fuse FU, a control circuit, a main contactor contact, and a thermal element of a thermal relay in sequence. Here, the thermal element of the thermal relay is arranged on the main circuit of the single-phase motor, and the normally closed contact 60 of the thermal relay is connected in series with the control circuit and in parallel with the control coil of the time relay.

[0024] The auxiliary capacitor 30 is of model CD60, and three groups are arranged in parallel.

[0025] like Figure 2 As shown, the working principle of the utility model is: start the power button, that is, press the second normally open switch Sb2, then the control circuit forms a path, the control coil of the main contactor starts to work, the contacts of the main contactor corresponding to the main circuit are closed, the main coil and the auxiliary coil are energized, and the motor starts to start.

[0026] When the thermal element of the thermal relay senses that the main circuit temperature is too high, that is, overheating due to large current, the normally closed contact 60 of the thermal relay starts / opens, thereby controlling the circuit to be disconnected, the control coil of the main contactor stops working, the main contactor contacts open, and the main circuit is disconnected.

[0027] When the time relay is still working when the set time is reached, that is, the auxiliary contactor contacts are in a closed state, that is, the control coil of the auxiliary contactor connected in series with the centrifugal switch 50 is energized, that is, the centrifugal switch 50 is in the circuit, which means that the actual closing of the centrifugal switch 50 exceeds the actual setting for the time relay. In order to protect the time relay, the normally closed contacts of the time relay disconnect the control circuit, and then the main circuit of the motor is disconnected.

[0028] Compared with the prior art, the utility model adds an auxiliary contactor for controlling the increase and decrease of the auxiliary capacitor 30 and a time relay for controlling the working time of the centrifugal switch 50, so as to provide double protection for the motor startup while protecting the normal startup of the motor. First, it protects the running capacitor 40 from burning out or starting slowly when the load is too large; second, when the centrifugal switch 50 exceeds the working time, that is, the motor has not reached the predetermined speed, proving that the load is too large or the starting failure occurs, the time relay controls the circuit break to ensure the normal operation of the motor; the starting torque of the motor is increased by the auxiliary capacitor 30, the protection of the motor winding is enhanced, and the economic loss is reduced; at the same time, it still has the ability to restart in the event of a startup failure, thereby improving the flexibility of the motor starting device.

[0029] The above description is only the preferred feasible embodiment of the utility model and is not intended to limit the scope of the patent application of the utility model. All equivalent changes, equivalent substitutions or modified changes within the technical spirit and principles suggested by the utility model should be included in the scope of patent protection covered by the utility model.

Claims

1. A single-phase motor starting device with a protective function, comprising a control circuit for controlling a main circuit switch of a single-phase motor, characterized in that: It also includes an auxiliary contactor, a time relay and an auxiliary capacitor. A group of normally open contacts of the auxiliary contactor are connected in series with the control coil of the time relay and in parallel with the control circuit; the auxiliary capacitor is connected in series with another group of normally open contacts of the auxiliary contactor and in parallel with the running capacitor of the single-phase motor, and the auxiliary capacitor is connected in parallel in multiple groups; the control coil of the auxiliary contactor is connected in series with the centrifugal switch of the single-phase motor; and the normally closed contacts of the time relay are connected in series with the control circuit.

2. A single-phase motor starting device with protection function according to claim 1, characterized in that: The control circuit is connected in series with a fuse.

3. The single-phase motor starting device with protection function according to claim 1 is characterized in that: It also includes a thermal relay, a thermal element of which is arranged on the main circuit of the single-phase motor, and a normally closed contact of the thermal relay is connected in series with the control circuit and in parallel with the control coil of the time relay.

4. The single-phase motor starting device with protection function according to claim 1 is characterized in that: The control circuit includes a first normally closed switch, a second normally open switch and a main contactor. The second normally open switch is connected in parallel with a group of contacts of the main contactor and in series with the first normally closed switch and the control coil of the main contactor. The remaining contacts of the main contactor are connected in series with the main circuit of the single-phase motor.

5. The single-phase motor starting device with protection function according to claim 1 is characterized in that: Fuses are respectively arranged on the main circuits of the single-phase motors.

6. A single-phase motor starting device with protection function according to any one of claims 1 to 5, characterized in that: The control circuit, auxiliary contactor, time relay and auxiliary capacitor are all arranged in the electrical box and connected with the single-phase motor connector through a wire.

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