JP2014185817A - Motor starter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an earth leakage breaker from malfunctioning.SOLUTION: A motor starter circuit 9 is used for starting a single-phase induction motor 3 that drives a refrigerator compressor 3 and that includes a starting coil 4 and a main coil 5. Furthermore, this motor starter circuit 9 includes a first relay 10 that can be connected to a commercial power supply 7 via an earth leakage breaker 8 and that connects or cuts off a power supply path from the commercial power supply 7 via the earth leakage breaker 8 to one end of the starting coil 4 and one end of the main coil 5. One end of a thermistor 12 is connected to the other end of the starting coil 4. The motor starter circuit 9 includes a second relay 11 connecting or cutting off a power supply path from the other end of the thermistor 12 and the other end of the main coil 5 to the commercial power supply 7 via the earth leakage breaker 8. In this case, if an internal temperature of a refrigerator decreases to a first temperature, the first relay 10 and the second relay 11 substantially simultaneously cut off the respective power supply paths.

Description

  The present invention relates to a motor starting circuit for starting a motor for driving a compressor.

  Conventionally, this type of motor starting circuit is used for starting a compressor provided in a refrigerator, for example, as described in Patent Document 1 below. Specifically, as shown in FIG. 5, the refrigerator 100 is connected to a commercial power source 104 via a leakage breaker 102. A thermistor 110 having a positive temperature characteristic is connected in series with a starting coil 112 for starting a single-phase induction motor 108 for driving the compressor 106 provided in the refrigerator 100. If the thermostat 116 is closed in a state where the thermistor 110 is cooled, the resistance value of the thermistor 110 is small, so that a current flows not only through the main coil 114 but also through the activation coil 112. Thereby, the compressor 106 starts.

  The thermistor 110 generates heat due to a current flowing through itself at the time of startup, and the resistance value of the thermistor 110 rapidly increases. As a result, energization to the starting coil 112 is cut off, and current flows only through the main coil 114. Thereafter, the single-phase induction motor 108 continues to rotate only by supplying current to the main coil 114.

Further, in the compressor 106, there may be a case where an electric leakage occurs due to, for example, an insulating deterioration of the coating of the main coil 114. ELCB 102, L a current value I _L of (live) terminal, the difference between the current value I _N flowing through the N (neutral) terminal | monitors the current difference | | [Delta] I [Delta] I | setting is predetermined When the value is greater than or equal to the value I _th (for example, 15 mA), the supply of electric power from the commercial power source 104 is cut off because leakage has occurred.

JP-A-54-79863

  However, in the conventional motor starting circuit, as shown in FIG. 6, when the thermostat 116 is opened due to a temperature drop and the compressor 106 is stopped, the counter electromotive force generated in the single-phase induction motor 108 causes a current to flow to the N terminal side. There is a problem that the earth leakage breaker 102 may malfunction.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a motor starting circuit that can prevent malfunction of an earth leakage circuit breaker.

  In order to achieve the above object, one aspect of the present invention is a motor for driving a refrigerator compressor, which is used at the time of starting a motor having a starting coil and a main coil, and is connected to a commercial power source via an earth leakage breaker. A connectable motor starting circuit, wherein the first switch means connects or cuts off an energization path from the commercial power source to one end of the starting coil and one end of the main coil via the leakage breaker And one end of a thermistor is connected to the other end of the starting coil, and an energization path from the other end of the thermistor and the other end of the main coil to the commercial power supply via the earth leakage breaker. Second switch means for connecting or disconnecting, and when the inside of the refrigerator is lowered to a predetermined first temperature, the first switch means and the second switch means Substantially simultaneously shut off the current path respectively.

  According to the above aspect, it is possible to prevent malfunction of the earth leakage breaker.

It is a figure which shows the structure of the circuit for motor starting which concerns on 1st embodiment. It is a figure which shows the structure of the circuit for motor starting which concerns on 2nd embodiment. It is a figure which shows the structure of the circuit for motor starting which concerns on 3rd embodiment. It is a figure which shows the structure of the circuit for motor starting which concerns on 4th embodiment. It is a figure which shows the structure of the conventional circuit for motor starting. It is a figure which shows the problem of the circuit for motor starting of FIG.

(Introduction)
The inventor of the present invention repeatedly investigated the reason why the leakage breaker 102 malfunctioned when the thermostat 116 was opened and the compressor 106 was stopped in the motor starting circuit of FIG. As a result of the experiment, the following (1) was found.

(1) As is well known, when the single-phase induction motor 108 is rotated, a current is generated in the motor 108 due to the counter electromotive force. When the compressor 106 is stopped (that is, when the thermostat 116 is opened), a voltage is transiently generated in the motor 108 due to the counter electromotive force. This transient voltage is added to the power supply voltage (AC 100 V). Moreover, since the thermostat 116 is open, since the current value I _L that flows through the L terminals is zero, their current difference | [Delta] I | is likely the set value I _th or more. As a result, the earth leakage breaker 102 is operated.

  Based on the above experimental results, the present inventors have come up with the motor starting circuit according to the first to fourth embodiments.

(First embodiment)
First, the motor starting circuit according to the first embodiment will be described in detail.

(Constitution)
In FIG. 1, a refrigerator 1 includes a compressor 2 that constitutes a refrigeration cycle. The compressor 2 includes a single phase induction motor 3. The single-phase induction motor 3 includes a starting coil 4 that is energized only when the motor 3 is started, and a main coil 5 that is energized while the motor 3 is starting.

  The refrigerator 1 is provided with a thermostat 6 for switching the operation / stop of the compressor 2. The thermostat 6 is closed while the refrigerator 1 is not cooled (that is, when the ambient temperature is not low), and connects the energization path. On the other hand, when the refrigerator 1 is sufficiently cooled (that is, when the ambient temperature is low), the refrigerator 1 is opened and the energization path is interrupted.

  A commercial power supply 7 is drawn into a space (typically a kitchen) where the refrigerator 1 is installed. The commercial power source 7 is provided with a leakage breaker 8. Here, the earth leakage breaker 8 may be a so-called breaker installed in the house, or may be a plug type earth leakage breaker that can be plugged into an outlet.

In addition, a motor starting circuit 9 is attached to the single-phase induction motor 3 and is electrically connected to the earth leakage breaker 8 and the motor 3. The motor starting circuit 9 includes a first terminal T _{1 to a} seventh terminal T ₇ .

The terminal T ₁ is connected to the L terminal of the commercial power source 7, and the terminal T ₂ is connected to the N terminal of the commercial power source 7 via the leakage breaker 8. The terminal T ₃ is electrically connected to one end of the activation coil 4 and one end of the main coil 5. The terminal T ₄ is electrically connected to the other end of the activation coil 4, and the terminal T ₅ is electrically connected to the other end of the main coil 5. The terminal T ₆ is electrically connected to one end of the thermostat 6 and the terminal T ₇ is electrically connected to the other end.

  The motor starting circuit 9 further includes a first relay 10 as an example of a first switch means, a second relay 11 as an example of a second switch means, a thermistor (PTC thermistor) 12 having a positive temperature characteristic, It has.

The relay 10 includes a switch (contact point) 10a and a coil 10b. One end of the switch 10a to the terminal T _1, the other end to the terminal T _3, are electrically connected. Coil 10b is provided between the terminals T ₁ and the terminal T _6. When a current is flowing through the coil 10b, the switch 10a is kept closed, and the energization path between the commercial power source 7 and one end of the starting coil 4 and one end of the main coil 5 is connected. To do. On the contrary, when the energization to the coil 10b is cut off, the switch 10a is opened to cut off this energization path.

The relay 11 includes a switch (contact point) 11a and a coil 11b. One end of the switch 11a is electrically connected to the respective other end and terminal T ₅ of the thermistor 12. The other end of the switch 11a is electrically connected to the terminal T _2. Coil 11b is provided between the terminal T ₂ and the terminal T _7. When a current is flowing through the coil 11b, the switch 11a is kept closed, and the current path between the other end of the thermistor 12 and the other end of the main coil 5 and the commercial power source 7 is connected. Conversely, when the energization to the coil 11b is cut off, the switch 11a is opened to cut off this energization path.

One end of the thermistor 12 is electrically connected to the terminal T _4, and the other end is electrically connected to one end of the switch 11 a, whereby the thermistor 12 is connected in series with the activation coil 4.

(Operation)
The motor starting circuit 9 configured as described above operates as follows. When the inside temperature of the refrigerator 1 is higher than the second temperature T _B, in order to lower the inside temperature, the thermostat 6 is closed. Here, before the thermostat 6 is closed, the switches 10a and 11a are both opened. When the thermostat 6 is closed, the current supplied from the commercial power source 7 flows to the coils 10b and 11b via the leakage breaker 8, so that the switches 10a and 11a are closed. Thereby, a current is also supplied to the compressor 106.

  Before the thermostat 6 is closed, the resistance value of the thermistor 12 is relatively small. Therefore, current flows through both the starting coil 4 and the main coil 5 of the compressor 106. As a result, the single-phase induction motor 3 starts to rotate and the compressor 106 starts.

  When a current flows through the thermistor 12, the thermistor 12 generates heat. As a result, since the resistance value of the thermistor 12 increases rapidly, the energization to the starting coil 4 is cut off, and a current flows only through the main coil 5. Thereafter, the single-phase induction motor 3 continues to rotate only by supplying current to the main coil 5.

When the compressor 2 is driven, the temperature inside the refrigerator 1 gradually decreases, and when the inside of the refrigerator 1 is sufficiently cooled and falls below the first temperature T _A (T _A <T _B ), the thermostat 6 is opened. Thereby, since electricity supply to coil 10b, 11b is interrupted | blocked, switch 10a, 11a opens simultaneously. As a result, energization of the single-phase induction motor 3 is also cut off, and the compressor 106 is stopped.

By the way, in the compressor 2, an electrical leakage may occur due to, for example, an insulating deterioration of the coating of the main coil 5 or the like. The earth leakage breaker 8 monitors the difference | ΔI | between the current value I _L at the _L terminal and the current value I _N flowing through the N terminal, and the current difference ΔI is equal to or greater than a predetermined set value I _th (for example, 15 mA). Then, the power supply from the commercial power source 7 is cut off.

(Action / Effect)
In the case of the conventional motor starting circuit (see FIG. 6), as described above, when the compressor 106 is stopped, the leakage breaker 102 may be operated due to the counter electromotive force.

On the other hand, according to the motor starting circuit 9 of FIG. 1, when the thermostat 6 is opened, the switches 10a and 11a are simultaneously opened. As a result, both the current value I _L and the current value I _N become zero, and the current difference | ΔI | can be prevented from exceeding the set value I _th . Therefore, malfunction of the earth leakage circuit breaker 8 resulting from back electromotive force can be prevented.

  Further, according to the motor starting circuit 9, a large current of several amperes is required for driving the single-phase induction motor 3, but only a small current (about several mA) flows through the thermostat 6. Therefore, a small thermostat 6 can be used for the motor starting circuit 9.

  Further, according to the motor starting circuit 9, the relays 10 and 11 and the thermistor 12 are accommodated in the same casing. This makes it possible to provide a motor starting circuit 9 that can be easily handled by a refrigerator manufacturer and is easy to use.

(Appendix)
The motor starting circuit 9 controls energization to the compressor 2 by the relays 10 and 11. However, the present invention is not limited to this, and the energization to the compressor 2 may be controlled by other switch means such as a transistor, a thyristor, or a triac. Further, on / off of the switch means may be controlled by a microcomputer. In this regard, the same applies to the second and subsequent embodiments.

  In the above description, the motor starting circuit 9 is described as including the first relay 10 as an example of the first switch means and the second relay 11 as an example of the second switch means. However, the present invention is not limited to this, and in the motor starting circuit 9, the two relays 10 and 11 may be replaced with one relay unit as described below. This relay unit includes a plurality of contact pairs as first switch means and second switch means, and at least one coil for driving these contact pairs.

(Second embodiment)
Next, the motor starting circuit according to the second embodiment will be described.

  In FIG. 2, the refrigerator 1 is different from that of FIG. 1 in that a thermostat 6 </ b> A is provided instead of the thermostat 6. In addition, the single-phase induction motor 3 in FIG. 2 is different in that a motor starting circuit 9A is attached instead of the motor starting circuit 9 in FIG. There is no difference other than the above. Therefore, in FIG. 2, the same reference numerals are given to the components corresponding to the configuration of FIG. Hereinafter, the differences will be described in detail.

One end of the thermostat 6 </ b> A is connected to the L terminal of the commercial power supply 7 via the leakage breaker 8. The other end of the thermostat 6A is connected to the terminal T ₁ of the motor starting circuit 9A.

The motor start-up circuit 9A, the earth leakage breaker 8, to a single-phase induction motor 3 is electrically connected, and a first terminal T ₁ to the fifth terminal T _5.

Terminal T ₁ is connected to the other end of the thermostat 6A. The other terminals T _{2 to} T ₅ are connected as described in the first embodiment.

  Similarly to the first embodiment, the motor starting circuit 9A has a first relay 10 as an example of the first switch means, a second relay 11 as an example of the second switch means, and a positive temperature characteristic. A thermistor (PTC thermistor) 12.

In the relay 10, one terminal of the switch 10a to the terminal T _1, the other end to the terminal T _3, are electrically connected. Further, one end of the coil 10b and the terminal T _1, the other end and one end of the coil 11b, are electrically connected. In such a relay 10, when a current flows through the coil 10 b, the switch 10 a maintains a closed state, and the commercial power supply 7, one end of the activation coil 4, and one end of the main coil 5 Connect the energization path between. On the contrary, when the energization to the coil 10b is cut off, the switch 10a is opened to cut off this energization path.

In the relay 11, one end of the switch 11a is electrically connected to the respective other end and terminal T ₅ of the thermistor 12. The other end of the switch 11a is electrically connected to the terminal T2. One end of the coil 11b and the other end of the coil 10b, the other end and the terminal T _2, are electrically connected. In such a relay 11, when a current flows through the coil 11 b, the switch 11 a is kept closed, and the other end of the thermistor 12 and the other end of the main coil 5, and the energization path of the commercial power supply 7. Connect. Conversely, when the energization to the coil 11b is cut off, the switch 11a is opened to cut off this energization path.

  The thermistor 12 is connected in series with the activation coil 4 as in the first embodiment.

(Operation)
In the motor starting circuit 9A configured as described above, the compressor 2 is started in the same procedure as in the first embodiment. When the compressor 2 is driven, the temperature in the refrigerator 1 gradually decreases, and when the refrigerator 1 is sufficiently cooled, the thermostat 6A is opened. Thereby, since electricity supply to coil 10b, 11b is interrupted | blocked, switch 10a, 11a opens simultaneously. As a result, energization of the single-phase induction motor 3 is also cut off, and the compressor 106 is stopped.

(Action / Effect)
As described above, also in the motor starting circuit 9A, when the thermostat 6A is opened, the switches 10a and 11a are simultaneously opened. As a result, both the current value I _L and the current value L _N become zero, and it is possible to prevent the current difference | ΔI | from exceeding the set value I _th . Therefore, malfunction of the earth leakage circuit breaker 8 resulting from back electromotive force can be prevented.

  The thermostat 6A itself has the same configuration as the thermostat 116 of the conventional motor starting circuit shown in FIG. Thus, according to the motor starting circuit 9, there is also an effect that the number of change points from the conventional one can be reduced.

In the above description, the motor starting circuit 9A is described as including the first relay 10 as an example of the first switch means. However, not limited thereto, the motor starting circuit 9A, and the terminal T ₁ and the terminal T ₃ by removing the first relay 10 is connected directly, electrically between one end of the coil 11b are terminals T _1, T ₃ May be connected to each other. In this case, an example of the first switch means is the thermostat 6 </ b> A, and an example of the second switch means is the second relay 11. Note that this point also applies to the following third embodiment.

(Third embodiment)
Next, the motor starting circuit according to the third embodiment will be described.

  The single-phase induction motor 3 in FIG. 3 is different in that a motor starting circuit 9B is attached instead of the motor starting circuit 9A in FIG. Further, the motor starting circuit 9B is generally different from the motor starting circuit 9A of FIG. 2 in that the thermistor 12 is not a component. There is no difference other than the above. Therefore, in FIG. 3, components corresponding to those in FIG. Further, since the operation, action, and effect of the motor starting circuit 9B are clear from the description of the second embodiment, the description thereof is omitted.

(Fourth embodiment)
Next, a motor starting circuit according to the fourth embodiment will be described.

(Constitution)
In FIG. 4, the refrigerator 1 includes a compressor 2 having a single-phase induction motor 3 as described in the first embodiment. The single-phase induction motor 3 includes the aforementioned start-up coil 4 and main coil 5. As described in the first embodiment, the thermistor 12 is connected to the activation coil 4 in series. In the installation space of the refrigerator 1, a commercial power source 7 to which a leakage breaker 8 is attached is provided.

The single-phase induction motor 3 is provided with a motor starting circuit 9C. The motor starting circuit 9C is electrically connected to the earth leakage breaker 8 and the motor 3. The motor starting circuit 9C includes a first terminal T _{1 to a} fourth terminal T ₄ .

The terminal T ₁ is connected to the L terminal of the commercial power source 7, and the terminal T ₂ is connected to the N terminal of the commercial power source 7 via the leakage breaker 8. The terminal T ₃ is electrically connected to one end of the activation coil 4 and one end of the main coil 5. Terminal T ₄ is electrically connected to each of the other end of the thermistor 12 and the other end of the main coil 5.

  The motor starting circuit 9C further includes a first thermostat 10C as an example of the first switch means and a second thermostat 11C as an example of the second switch means.

One end to the terminal T ₁ of the first thermostat 10C, the other end to the terminal T _3, are electrically connected. One end of the second thermostat 11C to the terminal T _2, the other end to the terminal T _4, are electrically connected. Both of these thermostats 10C, 11C is open at a first temperature T _A of the refrigerator of the refrigerator 1 can be regarded as sufficiently cooled, the commercial power source 7, and one end of the one end and the main coil 5 Starting coil 4 Are connected to each other, and the other end of the thermistor 12 and the other end of the main coil 5 are connected to the commercial power source 7. Moreover, when the inside of the refrigerator 1 becomes higher than the second temperature T _B (T _B > T _A ), the refrigerator 1 is closed, and these energization paths are interrupted.

(Operation)
The motor starting circuit 9C configured as described above operates as follows. When the inside temperature is higher than the second temperature T _B, the thermostat 10C, 11C are closed. As a result, the current supplied from the commercial power source 7 is supplied to the compressor 106 via the leakage breaker 8.

  Here, before both the thermostats 10C and 11C are closed, the resistance value of the thermistor 12 is relatively small, so that a current flows through both the starting coil 4 and the main coil 5. As a result, the single-phase induction motor 3 starts to rotate and the compressor 2 starts.

  When a current flows through the thermistor 12, the resistance value of the thermistor 12 suddenly increases due to self-heating, so that the current flows only through the main coil 5. Thereafter, the single-phase induction motor 3 continues to rotate only by supplying current to the main coil 5.

After driving the compressor 2, the inside temperature is less than the first temperature T _A, both the thermostat 10C, 11C is opened. Thereby, since the electricity supply to the single phase induction motor 3 is interrupted, the compressor 2 is stopped.

(Action / Effect)
Even the motor starting circuit 9C, the inside temperature falls below the first temperature T _A, both the thermostat 10C, 11C opens substantially simultaneously. As a result, both the current value I _L and the current value L _N become zero, and it is possible to prevent the current difference | ΔI | from exceeding the set value I _th . Therefore, malfunction of the earth leakage circuit breaker 8 resulting from back electromotive force can be prevented.

(Appendix)
In the fourth embodiment, it has been described that the thermistor 12 is not connected to the motor starting circuit 9C but simply connected in series to the starting coil 4. However, the present invention is not limited to this, and the thermistor 12 may have the configuration of the motor starting circuit 9C.

  The motor starting circuit according to the present invention can prevent malfunction and is suitable for starting a compressor of a refrigerator.

DESCRIPTION OF SYMBOLS 1 Refrigerator 2 Compressor 3 Single phase induction motor 4 Coil for starting 5 Main coil 6, 6A Thermostat 7 Commercial power supply 8 Earth leakage breaker 9, 9A-9C Motor starting circuit 10 First relay 10C First thermostat 11 Second relay 11C Second Two thermostats 12 thermistors

Claims (4)

A motor for driving a compressor for a refrigerator, which is used when starting a motor having a start coil and a main coil, and is a motor start circuit that can be connected to a commercial power source via a leakage breaker,
First switch means for connecting or interrupting the current path between the commercial power source and one end of the activation coil and one end of the main coil via the earth leakage breaker;
One end of a thermistor is connected to the other end of the starting coil, and an energization path between the other end of the thermistor and the other end of the main coil and the commercial power supply via the leakage breaker is provided. A second switch means for connecting or disconnecting,
When the inside of the refrigerator is lowered to a predetermined first temperature, the first switch means and the second switch means cut off the respective energization paths substantially simultaneously.   The motor starting circuit according to claim 1, wherein the thermistor is included therein. When the refrigerator reaches the first temperature, the refrigerator is provided with a thermostat that cuts off the energization path and connects the energization path that is higher than the first temperature.
3. The motor starting circuit according to claim 1, wherein when the thermostat interrupts the energization path, the first switch means and the second switch means interrupt the respective energization paths substantially simultaneously.   The first switch means and the second switch means are each a thermostat that cuts off an energization path when the first temperature is reached and connects an energization path that reaches a second temperature higher than the first temperature. Or the motor starting circuit according to 2;

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