Contactless starter for single-phase alternating current motor

Abstract

The utility model discloses a contactless starter for a single-phase alternating-current motor, and belongs to the technical field of single-phase alternating-current motor starters. Comprising a bidirectional silicon controlled rectifier T and a positive temperature coefficient thermistor Rt, a first pole T1 of the bidirectional silicon controlled rectifier T is connected with a leading-out end M of a motor main winding, a second pole T2 of the bidirectional silicon controlled rectifier T is connected with a leading-out end S of a motor secondary winding, and a trigger pole G of the bidirectional silicon controlled rectifier T is connected with one end of the positive temperature coefficient thermistor Rt. And the other end of the positive temperature coefficient thermistor Rt is connected with a combined leading-out end Z of the main and secondary windings of the motor. The utility model has the advantages that the starting of the high-power motor can be stably and reliably supported, the failure risk caused by contact adhesion is solved by a contactless implementation mode, and meanwhile, a positive temperature coefficient thermistor in a secondary winding starting circuit is canceled, so that the starting of the high-power motor can be stably and reliably supported; as a positive temperature coefficient thermistor in the secondary winding starting circuit is removed, the cost of the starter can be remarkably reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of single-phase AC motor starters, and relates to a contactless starter, which is mainly used for starting a single-phase compressor motor, and can also be used for starting an ordinary single-phase AC induction motor, which is hereinafter collectively referred to as a single-phase AC motor. Background Art

[0002] A single-phase AC motor usually consists of a rotor and a stator consisting of a main winding and a secondary winding. In addition to starting the motor, the secondary winding can also continue to work during normal operation of the motor, so the complete secondary winding circuit of a single-phase AC motor can usually be represented by a parallel secondary winding operation circuit and a secondary winding starting circuit. If the secondary winding does not work during normal operation, the motor does not have a secondary winding operation circuit; the secondary winding starting circuit only works when the motor starts and needs to be disconnected after the motor starts.

[0003] The auxiliary winding circuit mentioned above participates in the work during starting, and the function of disconnecting after starting is realized by a starter. There are currently three common technical means for the starter of this single-phase AC motor: the first one is a contact relay starter, such as Figure 1 As shown in the figure, the single-phase AC motor in the figure is shown with a starting capacitor Cs, but the situation without a starting capacitor Cs is the same. In the figure, K represents a contact relay that controls the auxiliary winding starting circuit; the second type is a contactless starter realized by a positive temperature coefficient thermistor, such as Figure 2 As shown in the figure, Rt represents a positive temperature coefficient thermistor, which can realize the conduction of the auxiliary winding starting circuit at the beginning of starting. After the positive temperature thermistor heats up and causes the resistance to increase rapidly, the auxiliary winding starting circuit is basically disconnected, thereby realizing the starting function; the third type is a contactless starter based on a bidirectional thyristor, such as Figure 3 As shown, this type of starter is based on the contactless starter realized by the positive temperature coefficient thermistor Rt. By adding a bidirectional thyristor T in series in the auxiliary winding starting circuit, the auxiliary winding starting circuit can be completely disconnected by disconnecting the bidirectional thyristor T when the motor starting is completed.

[0004] Traditional starters in the form of current relays and voltage relays belong to the first technical means. The relay is only closed at starting and disconnected after starting is completed. This type of starter has two main problems: matching trouble and contact adhesion. The action control of the current relay is sensitive to the motor parameters, so it needs to be adapted and optimized for almost every different motor, which makes matching troublesome. Although the action of the voltage relay is relatively insensitive to the motor parameters, the problem of contact adhesion cannot be solved. The technical solution disclosed in U.S. Patent Publication No. US20060202786A1 involves this type of voltage relay, and the technical solution disclosed in Chinese Patent Publication No. CN206481237U is this type of current relay.

[0005] The second type of contactless starter implemented by the positive temperature coefficient thermistor solves the two problems of the contact relay starter very well. The positive temperature coefficient thermistor is connected in series in the secondary winding starting circuit. Its normal temperature resistance value is small, which can realize the secondary winding starting circuit to be turned on at the beginning of starting. When the current passes through, it generates heat and the temperature rises, and the resistance value increases accordingly. Further, when the temperature reaches near the Curie point, the resistance value of the positive temperature coefficient thermistor will become much larger than the normal temperature resistance value, which can basically disconnect the secondary winding starting circuit, thereby realizing the starting of the motor. The starter implemented by the positive temperature coefficient thermistor is not sensitive to the motor parameters, and motors with power range differences that are not particularly close can usually share the same starter, so the matching is simple, and there is no contact, which perfectly solves the problems of the contact relay starter. However, this type of starter also has its new problems: when the motor is operating normally, the positive temperature coefficient thermistor needs to continue to pass a certain current to maintain its high resistance state and keep the secondary winding starting circuit basically disconnected. This causes this type of starter to generate some unnecessary heat and power consumption for motor operation. Due to the huge application volume of this type of motor, the additional power consumption has brought about a huge waste of energy. In addition, there is another problem with this type of starter, which is power limitation. Due to the material properties of the positive temperature coefficient thermistor, the rated current that can pass through it is relatively limited. It can usually only be used to start small and medium power motors, and cannot achieve the starting of single-phase AC motors with too much power / current. Chinese Patent Publication No. CN2664281 introduces this type of contactless starter.

[0006] The extra energy consumption of the contactless starter realized by the above-mentioned positive temperature coefficient thermistor has spawned a new generation of power-free and low-power starters, and a third type of contactless starter based on bidirectional thyristor has appeared in the industry. This type of starter no longer needs to maintain the high resistance state of the positive temperature coefficient thermistor in the secondary winding starting circuit, which solves the problem of heat power consumption of the above-mentioned positive temperature coefficient thermistor, thereby avoiding unnecessary heat power consumption. An electronic low-power starter disclosed in Chinese Patent Publication No. CN201435703Y and a mutual inductance contactless starter disclosed in Chinese Patent Publication No. CN1294694C both belong to this category. However, this type of starter still has a big drawback so far, that is, there must be a positive temperature coefficient thermistor in the secondary winding starting circuit, otherwise the starter cannot work stably and reliably. Therefore, this type of starter also has the same current size limitation problem as the contactless starter based on the positive temperature coefficient thermistor, and cannot support the starting of motors with a larger power range. At the same time, through actual tests, it is found that compared with the contact relay starter without series resistor in the auxiliary winding starting circuit, the positive temperature coefficient thermistor in the auxiliary winding starting circuit of the third type of starter also has a certain weakening effect on the starting performance of the motor. The power application range problem caused by the limitation of the current passing capacity of the positive temperature coefficient thermistor has not been solved. From the patents and literature that can be queried at present, the existing contactless starters based on bidirectional thyristors need to retain the positive temperature coefficient thermistor connected in series in the auxiliary winding starting circuit without exception to achieve stable and reliable operation of the starter.

[0007] In view of the above-mentioned prior art, it is necessary to improve the structure of the starter of the existing single-phase AC motor. To this end, the applicant has made a useful design, and the technical solution to be introduced below is produced in this context. Utility Model Content

[0008] The utility model aims to provide a contactless starter for a single-phase AC motor, which has stable working performance, is safe and reliable, consumes less power and can withstand large current.

[0009] The purpose of the utility model is to achieve a contactless starter for a single-phase AC motor, comprising a bidirectional thyristor T and a positive temperature coefficient thermistor Rt, wherein the first pole T1 of the bidirectional thyristor T is connected to the motor main winding lead-out terminal M, the second pole T2 of the bidirectional thyristor T is connected to the motor secondary winding lead-out terminal S, the trigger pole G of the bidirectional thyristor T is connected to one end of the positive temperature coefficient thermistor Rt, and the other end of the positive temperature coefficient thermistor Rt is connected to the motor main and secondary windings combined lead-out terminal Z.

[0010] In a specific embodiment of the present invention, an inductor L is further included, one end of the inductor L is connected to the first pole T1 of the bidirectional thyristor T, and the other end of the inductor L is connected to the lead-out terminal M of the main winding of the motor.

[0011] In another specific embodiment of the utility model, the single-phase AC motor is connected to a starting capacitor Cs, and the contactless starter includes a bidirectional thyristor T and a positive temperature coefficient thermistor Rt, the first pole T1 of the bidirectional thyristor T is connected to one end of the starting capacitor Cs, the other end of the starting capacitor Cs is connected to the motor main winding lead-out terminal M, the second pole T2 of the bidirectional thyristor T is connected to the motor secondary winding lead-out terminal S, the trigger pole G of the bidirectional thyristor T is connected to one end of the positive temperature coefficient thermistor Rt, and the other end of the positive temperature coefficient thermistor Rt is connected to the combined lead-out terminal Z of the motor main and secondary windings.

[0012] In another specific embodiment of the present invention, an inductor L is further included, one end of the inductor L is connected to the first pole T1 of the bidirectional thyristor T, and the other end of the inductor L is connected to one end of the starting capacitor Cs.

[0013] In another specific embodiment of the utility model, a resistor R is further included, one end of the resistor R is connected to the first pole T1 of the bidirectional thyristor T, and the other end of the resistor R is connected to the trigger pole G of the bidirectional thyristor T and one end of the positive temperature coefficient thermistor Rt.

[0014] In another specific embodiment of the utility model, a resistor R1 is further included, one end of the resistor R1 is connected to the other end of the positive temperature coefficient thermistor Rt, and the other end of the resistor R1 is connected to the main and auxiliary windings of the motor and the lead-out terminal Z.

[0015] Due to the adoption of the above structure, the utility model has the following technical effects compared with the prior art: first, it can stably and reliably support the starting of high-power motors, perfectly solving the problem of contact adhesion of contact relay starters in the prior art, and the problem that the contactless starter based on positive temperature coefficient thermistor cannot effectively support the starting of high-power motors due to the limitation of its rated current, and its starting performance is weakened by the positive temperature coefficient thermistor. The contactless implementation method solves the failure risk caused by contact adhesion, and at the same time cancels the positive temperature coefficient thermistor in the auxiliary winding starting circuit, so that the starting of high-power motors can be stably and reliably supported; second, it also has significant advantages for the starting of small and medium-power motors that can be well supported in the prior art solution, because the positive temperature coefficient thermistor in the auxiliary winding starting circuit is removed, and this part occupies a large proportion of the cost of the starter, so the cost of the starter can be significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the technical solution of the existing contact relay starter;

[0017] Figure 2 The electrical schematic diagram of the existing contactless starter based on positive temperature coefficient thermistor;

[0018] Figure 3 The electrical schematic diagram of the existing contactless starter based on bidirectional thyristor;

[0019] Figure 4 This is an electrical schematic diagram of an embodiment of the utility model;

[0020] Figure 5 This is an electrical schematic diagram of another embodiment of the utility model;

[0021] Figure 6 This is an electrical schematic diagram of yet another embodiment of the utility model;

[0022] Figure 7 This is an electrical schematic diagram of another embodiment of the present utility model. DETAILED DESCRIPTION

[0023] The specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings, but the description of the embodiments is not a limitation of the technical solution. Any changes in form rather than substance based on the concept of the present invention should be regarded as the protection scope of the present invention.

[0024] In the following description, all concepts related to directionality (or orientation) such as up, down, left, right, front and back are referring to the position state of the figure being described, and are intended to facilitate public understanding. Therefore, they should not be understood as special limitations on the technical solutions provided by the present utility model.

[0025] Embodiment 1: The utility model relates to a contactless starter for a single-phase AC motor. Figure 4 In the figure, connection points A and B are the power input terminals, M to Z and S to Z represent the main winding and auxiliary winding of the single-phase AC motor respectively, M is the main winding lead-out terminal of the motor, S is the auxiliary winding lead-out terminal of the motor, and Z is the combined lead-out terminal of the main and auxiliary windings of the motor. T is a bidirectional thyristor, T1, T2, and G are the first pole, the second pole, and the trigger pole of the bidirectional thyristor T respectively; Rt is a positive temperature coefficient thermistor.

[0026] The first pole T1 of the bidirectional thyristor T is connected to the lead-out terminal M of the motor main winding, the second pole T2 of the bidirectional thyristor T is connected to the lead-out terminal S of the motor secondary winding, the trigger pole G of the bidirectional thyristor T is connected to one end of the positive temperature coefficient thermistor Rt, and the other end of the positive temperature coefficient thermistor Rt is connected to the combined lead-out terminal Z of the motor main and secondary windings. The positive temperature coefficient thermistor Rt is connected in series in the trigger pole circuit of the bidirectional thyristor T to control the current of the trigger pole G. The circuit from the lead-out terminal M of the motor main winding through the bidirectional thyristor T to the lead-out terminal S of the motor secondary winding constitutes the secondary winding starting circuit of the motor. For a single-phase AC motor, the secondary winding starting circuit needs to be turned on when the motor starts and disconnected after the motor completes starting.

[0027] When the external power supply is turned on, the external power supply is applied to the electric circuit composed of the first pole T1 of the bidirectional thyristor T, the trigger pole G, and the positive temperature coefficient thermistor Rt through the access point A and the access point B. At the beginning of power-on, the positive temperature coefficient thermistor Rt has not yet heated up, and its resistance is the resistance value at room temperature, which is in a relatively low state. At this time, the current in the trigger pole G is in a relatively high state, and the current value is sufficient to trigger the conduction of the T1 pole and the T2 pole of the bidirectional thyristor T. Therefore, the secondary winding starting circuit from the motor main winding lead-out terminal M through the bidirectional thyristor T to the motor secondary winding lead-out terminal S is turned on, and the motor starts to start.

[0028] After working for a period of time, the current flowing through the positive temperature coefficient thermistor Rt causes the positive temperature coefficient thermistor Rt to heat up and its resistance value increases rapidly. Correspondingly, the trigger current in the trigger pole G of the bidirectional thyristor T decreases. Because the trigger current is a power frequency sinusoidal current, the decrease in the trigger current eventually causes the conduction angle of the bidirectional thyristor T to gradually decrease. As the temperature of the positive temperature coefficient thermistor Rt further increases, its resistance value continues to increase rapidly, causing the trigger current in the trigger pole G of the bidirectional thyristor T to further decrease. Ultimately, the bidirectional thyristor T cannot be turned on due to the small trigger current. At this time, the secondary winding starting circuit is disconnected and the motor start is completed.

[0029] Example 2: Please see Figure 5 This embodiment is based on the embodiment 1, and adds resistors R and R1. By adjusting the starting value of the trigger current and the current change during the starting process, the triggering conduction and disconnection performance of the bidirectional thyristor T is adjusted and optimized to achieve better starting control.

[0030] Specifically, one end of the resistor R is connected to the first pole T1 of the bidirectional thyristor T, and the other end of the resistor R is connected to the trigger pole G of the bidirectional thyristor T and one end of the positive temperature coefficient thermistor Rt. One end of the resistor R1 is connected to the other end of the positive temperature coefficient thermistor Rt, and the other end of the resistor R1 is connected to the combined lead-out terminal Z of the main and secondary windings of the motor.

[0031] In addition, an inductor L is added, one end of which is connected to the first pole T1 of the bidirectional thyristor T, and the other end of which is connected to the motor main winding lead-out terminal M. The inductor L limits the change rate of the bidirectional thyristor conduction current flowing through the first pole T1 and the second pole T2 of the bidirectional thyristor T, thereby better protecting the bidirectional thyristor T from working reliably.

[0032] The resistor R, resistor R1 and inductor L can be added separately to realize their respective adjustment functions. A more common implementation method is to combine two or three of them and increase them at the same time to comprehensively optimize the starter.

[0033] Example 3: Please refer to Figure 6 In this embodiment, the single-phase AC motor has a starting capacitor Cs. The first pole T1 of the bidirectional thyristor T is connected to one end of the starting capacitor Cs, the other end of the starting capacitor Cs is connected to the motor main winding lead-out terminal M, the second pole T2 of the bidirectional thyristor T is connected to the motor secondary winding lead-out terminal S, the trigger pole G of the bidirectional thyristor T is connected to one end of the positive temperature coefficient thermistor Rt, and the other end of the positive temperature coefficient thermistor Rt is connected to the motor main and secondary winding combined lead-out terminal Z. The working principle of this embodiment is exactly the same as that of embodiment 1.

[0034] See also Figure 7 Similarly, when a single-phase AC motor has a starting capacitor Cs, by adding resistor R, resistor R1 and inductor L individually or in combination, the starting performance of the starter can also be optimized and adjusted to achieve a more stable and reliable starting function.

Claims

1. A contactless starter for a single-phase AC motor, characterized in that: The invention comprises a bidirectional thyristor T and a positive temperature coefficient thermistor Rt, wherein the first pole T1 of the bidirectional thyristor T is connected to the lead-out terminal M of the main winding of the motor, the second pole T2 of the bidirectional thyristor T is connected to the lead-out terminal S of the secondary winding of the motor, the trigger pole G of the bidirectional thyristor T is connected to one end of the positive temperature coefficient thermistor Rt, and the other end of the positive temperature coefficient thermistor Rt is connected to the combined lead-out terminal Z of the main and secondary windings of the motor.

2. The contactless starter for a single-phase AC motor according to claim 1, characterized in that: It also includes an inductor L, one end of which is connected to the first pole T1 of the bidirectional thyristor T, and the other end of which is connected to the lead-out terminal M of the main winding of the motor.

3. The contactless starter for a single-phase AC motor according to claim 1, wherein the single-phase AC motor is connected to a starting capacitor Cs, and is characterized in that: The contactless starter includes a bidirectional thyristor T and a positive temperature coefficient thermistor Rt, wherein the first pole T1 of the bidirectional thyristor T is connected to one end of a starting capacitor Cs, the other end of the starting capacitor Cs is connected to a lead-out terminal M of a motor main winding, the second pole T2 of the bidirectional thyristor T is connected to a lead-out terminal S of a motor secondary winding, the trigger pole G of the bidirectional thyristor T is connected to one end of the positive temperature coefficient thermistor Rt, and the other end of the positive temperature coefficient thermistor Rt is connected to a combined lead-out terminal Z of the motor main and secondary windings.

4. The contactless starter for a single-phase AC motor according to claim 3, characterized in that: It also includes an inductor L, one end of which is connected to the first pole T1 of the bidirectional thyristor T, and the other end of which is connected to one end of the starting capacitor Cs.

5. The contactless starter for a single-phase AC motor according to claim 1 or 3, characterized in that: It also includes a resistor R, one end of which is connected to the first pole T1 of the bidirectional thyristor T, and the other end of which is connected to the trigger pole G of the bidirectional thyristor T and one end of a positive temperature coefficient thermistor Rt.

6. The contactless starter for a single-phase AC motor according to claim 1 or 3, characterized in that: It also includes a resistor R1, one end of which is connected to the other end of the positive temperature coefficient thermistor Rt, and the other end of the resistor R1 is connected to the main and auxiliary windings of the motor and the lead-out terminal Z.

Images