JP2578817Y2 - Motor start circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor starting circuit for a single-phase AC induction motor or a phase-separating motor.

[0002]

2. Description of the Related Art As is well known, a drive circuit for a single-phase AC induction motor or a phase-separated motor is provided with a main coil for performing a steady rotation of the motor and a starting coil that operates only when the motor is started. When the motor is started, the starting coil is driven by the motor starting circuit to rotate the motor, and the starting coil is disconnected from the input circuit when the rotation speed of the motor reaches a steady rotation.

By the way, power is supplied to the motor starting circuit even during steady rotation of the motor. Particularly, in a motor such as a refrigerator which operates continuously for a long time, the power loss due to the power supplied to the starting circuit is reduced. It is necessary to make it smaller. For this reason, a triac is used in a recent motor starting circuit, and a device for minimizing power loss has been devised.

A motor starting circuit using a triac is known from Japanese Patent Application Laid-Open No. 61-39874. As shown in FIG. 5, the motor starting circuit disclosed in this publication uses a first AC power supply.
The starting coil 3, the capacitor 4, and the triac 5 are connected in series between the input terminal 1 and the second input terminal 2, and the bias resistor 8 is connected between the second terminal 6 and the gate terminal 7 of the triac 5, Between the gate terminal 7 of the triac 5 and the input terminal of the starting coil 3 (the input terminal 1 side), a switch circuit 10 for controlling on / off of the gate of the triac 5 is provided.

In this circuit, when the motor is started, the gate of the triac 5 is opened by the operation of the switch circuit 10 to energize the starting coil 3 to start the rotation of the motor, and a predetermined time has elapsed from the start of the rotation of the motor. When the rotation of the motor reaches the steady rotation, the gate of the triac 5 is closed to stop the operation of the starting coil 3, and the steady rotation of the motor is continued by driving the main coil (not shown).

[0006]

However, the switch circuit 10 of the conventional motor starting circuit has a very small number of components because various circuit elements such as a bridge circuit of a diode, a capacitor and an SCR are complicatedly combined. In addition to the high number of parts, the circuit cost is high, and a problem arises in the reliability of the circuit operation due to the large number of parts. In particular, since motors such as refrigerators are used under severe conditions continuously for 100,000 hours or more, reliability is given particular importance,
As described above, the greater the number of parts, the more the problem of reliability arises. Therefore, the development of a highly reliable motor starting circuit with a small number of parts is desired.

[0007] The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to reduce power loss,
It is another object of the present invention to provide a highly reliable motor starting circuit having a small number of components.

[0008]

The present invention is configured as follows to achieve the above object. That is, the present invention provides a motor including an AC power supply for a motor, a starting coil connected to a first input terminal of the AC power supply and operating only when the motor is started, and a main coil for performing a steady rotation drive of the motor. In a motor starting circuit incorporated in a driving circuit, the motor starting circuit includes a triac, a bias resistor, and a positive temperature coefficient thermistor, and a first terminal of the triac is connected to an output end of a starting coil and a second terminal of the triac. The terminals are connected to the second input terminal side of the AC power supply, respectively. A bias resistor is interposed between the gate of the triac and the second terminal, and is connected between the gate of the triac and the input end of the starting coil. Is provided with a positive temperature coefficient thermistor, which flows during rotation driving of the motor
Heating resistor that generates heat by current
This heating resistor is connected to the PTC thermistor.
Connected in parallel with a series connection with a bias resistor
It is configured as a feature .

[0009]

In the present invention having the above structure, when the motor is started, the positive temperature coefficient thermistor is in a normal temperature state and has a small resistance, so that a large current flows through the positive temperature coefficient thermistor and the current is applied to the bias resistor. As a result, the voltage between both ends of the bias resistor, that is, the gate voltage of the triac is increased to the operating voltage or more, and the gate of the triac is opened. Then, power is supplied to the starting coil, and rotation of the motor is started by the operation of the starting coil. A short time after the start of rotation of the motor, the rotation speed of the motor is increased and the motor enters a steady rotation state. Increase rapidly. Due to this increase in the resistance, the current applied to the bias resistor through the positive temperature coefficient thermistor becomes very small, and the gate voltage of the triac becomes lower than the operating voltage. As a result, the gate of the triac is closed, the operation of the starting coil is stopped, the motor driving coil is switched from the starting coil to the main coil, and the motor rotates steadily. this
During the steady rotation of the motor, the PTC thermistor is a heating resistor
Is heated by the heat of
Are kept closed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same circuit parts as those in the conventional example are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 1 shows a first embodiment of a motor starting circuit according to the present invention in a motor driving circuit. The input terminal of the starting coil 3 is connected to the first input terminal 1 of the AC power supply 11, Are connected to the first terminal 9 side of the triac 5. In the figure, reference numeral 11 denotes an AC power supply of a motor having an effective value of 100 V, 12 denotes a switch for starting and stopping the motor, and 13 denotes a main coil of the motor. Note that the capacitor 4 may be omitted in some cases.

The present embodiment is different from the conventional example in that the switch circuit 10 of the conventional example is replaced with a positive temperature coefficient thermistor 14 and a low heat generation for heating the positive temperature coefficient thermistor 14.
An antibody 15 is provided, and the other configuration is the same as that of the conventional example. The positive temperature coefficient thermistor 14 is interposed between the gate terminal 7 of the triac 5 and the input terminal of the starting coil 3 and has a resistance of several hundred Ω at normal temperature, 800 Ω in this embodiment, and a temperature of approximately 90 ° C. In this embodiment, the resistance value is 103 times the initial resistance value in the normal temperature state, and is 800 KΩ or more. Also, Triac 5
Are formed to turn on the gate when the voltage applied to the gate is 1 to 10 V.

[0012] Next will be described the dynamic <br/> operation by the thermistor 14. When the switch 12 is closed, the AC power supply 11
Is applied to the positive temperature coefficient thermistor 14. Since this positive temperature coefficient thermistor 14 is initially at room temperature,
As shown in the figure, since the resistance is as low as 800 Ω,
As a result of the flow of a large current (for example, 125 mA), the voltage across the bias resistor 8, that is, the gate voltage of the triac 5, is raised to the operating voltage range, and the triac 5
Gate is opened.

Then, the current from the AC power supply 11 is supplied to the starting coil 3, and the operation of the starting coil 3 starts the rotation of the motor.

Since a large amount of current is applied to the positive temperature coefficient thermistor 14, the temperature rises sharply approximately 1.0 to 1.5 seconds after the start of energization, as shown in FIG.
Converges to a temperature of 90 ° C. Due to the rapid temperature rise of the positive temperature coefficient thermistor 14, the resistance value of the positive temperature coefficient thermistor 14 is reduced as shown in FIG.
As shown in the figure, when approximately 1.5 seconds have passed since the motor started,
It reaches 800 KΩ and converges. After 1.5 seconds from the start of the motor, the rotation speed of the motor has reached a steady rotation speed, and the value of the current passing through the positive temperature coefficient thermistor 14 is very small due to the rapid increase in the resistance value of the positive temperature coefficient thermistor 14. As a result, the gate voltage of the triac 5 becomes lower than the operating voltage, for example, 0.2 V or less, the gate of the triac 5 is closed, and the current supply to the starting coil 3 is cut off. At this time, the rotation of the motor has shifted to the steady rotation state, and the steady rotation of the motor is continuously and stably performed by the rotation drive of the main coil 13. During the normal rotation operation of the motor, since a small current continues to flow through the positive temperature coefficient thermistor 14, the temperature of the positive temperature coefficient thermistor 14 is maintained at approximately 90 ° C., the resistance value of 800 KΩ is maintained, and the triac 5 is maintained.
The gate closing operation state is maintained stably.

In this embodiment, the power loss of the positive temperature coefficient thermistor 14 during the steady operation of the motor is very small, and the power loss of the motor starting circuit can be made sufficiently small.

The present inventor omitted the triac 5, and instead of the triac 5, a positive characteristic thermistor 14 was connected in series to the starting coil 3 to form a motor starting circuit. The loss in the positive characteristic thermistor was 3W. It was a pretty big loss. On the other hand, by combining the triac 5 and the positive characteristic thermistor 14 as in this embodiment,
The loss of the motor starting circuit can be made extremely small,
In particular, it is suitable as a motor starting circuit for a refrigerator or the like that performs long-term continuous operation.

The characteristic feature in this embodiment is a this with a positive temperature coefficient thermistor 14 and the thermal heating resistors 15 coalescing provided. In this embodiment, the positive temperature coefficient thermistor 14 is formed using ceramics, and the heating resistor 15 is formed by forming a resistance pattern on the surface of the ceramics by using appropriate means such as printing or vapor deposition. 15 and the positive temperature coefficient thermistor 14 are thermally united. One end of the heating resistor 15 is connected to a connection between the positive temperature coefficient thermistor 14 and the starting coil 3, and the other end of the heating resistor 15 is connected to the second terminal 6 of the triac 5 and the bias resistor 8. Connected to the unit. In other words, the low fever antibody 15 is a positive temperature coefficient thermistor.
14 and bias low antibody 8 connected in series
Have been.

In this embodiment, the rotation start operation is performed at the time of starting the motor by operating as described above. However, when the motor is in a steady operation state, the small current flowing through the positive characteristic thermistor 14 causes the positive characteristic thermistor 14 to operate. Heat generation is continued, but at this time, the current flowing through the heating resistor 15 causes the heating resistor 15 to generate heat, and the heat of the heating resistor 15 is transmitted to the PTC thermistor 14, and the temperature of the PTC thermistor 14 decreases. Is prevented.

The positive temperature coefficient thermistor using the heating resistor 15
At the time of keeping the temperature of 14, the current flows through the heating resistor 15 to cause power loss in the heating resistor.However, due to the heat retention effect, the current flowing to the PTC thermistor 14 having a very large resistance value is reduced. since it is able to power loss generated in the PTC thermistor 14 smaller, as a result, low heat generation to the positive characteristic thermistor 14
The total power loss of the motor starting circuit provided with the antibody 15 can be reduced by using the positive temperature coefficient thermistor 14 without the heat-generating low antibody 15.
It can be made smaller than a circuit provided with only
When the power loss in the circuit of this embodiment provided with the heat generating low antibody 15 was measured, the power loss of the positive temperature coefficient thermistor 14 was 0.3 mW, the power loss of the heat generating resistor 15 was 0.2 W, and the power loss was very small. Thus, it was proved that the motor starting circuit could be operated.

[0020] The present invention is not limited to the above you施例, and may have aspects of various embodiments. For example, it has been described with a single-phase AC induction motor or phase separation motor Target is above you施例, motor starting circuit of the present invention is,
It is applied as a motor starting circuit for various other motors.

[0021]

[Effects of the Invention] The present invention is designed to control the closing operation of the triac simply by providing a positive temperature coefficient thermistor between the gate of the triac and the input end of the starting coil. The score can be significantly reduced, whereby the reliability of the circuit operation can be increased and the circuit cost can be significantly reduced.

Further, the power loss is very small, and it is particularly suitable as a motor starting circuit for a refrigerator or the like that performs long-term continuous operation.

Further, as described above, the present invention has a very small number of parts even when it is necessary to completely seal the motor starting circuit or perform resin casting depending on the use environment. Since circuit components such as capacitors, which are likely to hinder the operation, are not included, it is possible to seal the circuit and perform resin casting without any trouble.

Furthermore, since the heating resistor was thermally coalesced in PTC thermistor arrangement, it is possible to kept a PTC thermistor by the heating resistor, thereby, Mo
Ri Do and that can reduce the electric current of the positive characteristic thermistor during steady operation over data, moreover, the low heat generation
Connect antibodies in series with positive thermistors and low bias antibodies
By connecting to the body in parallel,
Power loss can be further reduced .

[Brief description of the drawings]

1 is a circuit diagram of a motor drive circuit including a circuit for real施例the motor starting circuit according to the present invention.

FIG. 2 is a characteristic diagram of a resistance value change of a positive temperature coefficient thermistor constituting the embodiment.

FIG. 3 is a characteristic diagram of a temperature change of the positive temperature coefficient thermistor.

FIG. 4 shows a conventional motor starting circuit using a triac .
FIG .

[Explanation of symbols]

 3 Starting coil 5 Triac 8 Bias resistor 11 AC power supply 13 Main coil 14 Positive thermistor 15 Heating resistor

Claims (1)

(57) [Scope of request for utility model registration] 1. A motor drive comprising: an AC power supply for a motor; a starting coil connected to a first input terminal of the AC power supply and operating only when the motor is started; and a main coil for performing a steady rotation drive of the motor. In a motor starting circuit incorporated in a circuit, the motor starting circuit includes a triac, a bias resistor, and a positive temperature coefficient thermistor, and a first terminal of the triac is connected to an output end of a starting coil and a second terminal of the triac. Is connected to the second input terminal side of the AC power supply, respectively, a bias resistor is interposed between the gate of the triac and the second terminal, and is connected between the gate of the triac and the input terminal side of the starting coil. PTC thermistor provided we are, the PTC thermistor during rotation of the motor
The heating resistors that generate heat due to the flowing current are thermally united.
The heating resistor is provided with
Connected in parallel with the series connection of the
Motor starting circuit, characterized in that is.