KR100598825B1 - Starting switch for electric motor - Google Patents

Abstract

The present invention relates to a start switch for an electric motor. The start switch for an electric motor according to the present invention includes a rectifier circuit for rectifying an input AC power source to a pulse current source, a silicon controlled rectifier element having an anode connected to a positive output terminal of the rectifier circuit, and a cathode connected to a negative output terminal of the rectifier circuit. A thermistor whose one end is connected to the anode of the silicon controlled rectifier and whose resistance increases with increasing ambient temperature, and at least one voltage drop element connected in series between the other end of the thermistor and the gate of the silicon controlled rectifier; do. The present invention uses thermistors having a smaller heat capacity than PTC as thermal resistance elements for electric motors, thereby reducing standby power consumption after operation and reducing power consumption reduced to tens of minutes due to amplification of transistors.

Description

Starting switch for electric motor {STARTING SWITCH FOR ELECTRIC MOTOR}

1 is a configuration diagram schematically showing the configuration of a conventional electric motor and a start switch.

2 is a view schematically showing a configuration of a start switch for an electric motor according to a first embodiment of the present invention.

3 is a waveform diagram showing an AC power supply waveform and a pulse wave waveform;

4 is a view schematically showing the configuration of a start switch for an electric motor according to a second embodiment of the present invention;

<Description of main parts of reference numerals>

10, 20: start switch

11: silicon controlled rectifier (SCR)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a start switch for an electric motor, and more particularly, to a start switch used for initially driving an electric motor employed in a refrigerator or the like.

1 is a configuration diagram schematically showing the configuration of a conventional electric motor and a start switch.

Referring to FIG. 1, the electric motor 2 has a main winding M and an auxiliary winding S therein, and each end of the main winding M and the auxiliary winding S has a node T1. Are connected in parallel, and the auxiliary winding S is connected in series with the PTC element 3. The power generated by the AC power supply 1 is supplied to the motor and the PTC element 3 through the terminals T1 and T3.

The PTC element 3 is a device having low resistance at ordinary times or at room temperature, but self-heating when a current flows, and the self-resistance value rapidly increases due to a temperature rise. Therefore, since the resistance value is low at the start-up, when a voltage is applied from the AC power supply 1, a large amount of current flows to the start-up winding S to start the electric motor 2. When a large amount of current flows to the starter winding S and the electric motor 2 starts to rotate, and the rotation rate of the electric motor is increased, the current flowing to the starter winding S becomes unnecessary. After the electric motor 2 is started, the PTC element 3 is heated by the current flowing through the starting winding S to increase the resistance value. As a result, the current flowing to the starting winding gradually decreases to a low level, whereby a constant current begins to flow to the main winding M. FIG.

However, in the case of the conventional starter switch, although the level of the current is reduced due to the characteristics of the PTC element 3, even though it is a low level, unnecessary current continues to flow and power of several watts (W) is continuously consumed. In addition, since the PTC element generates heat continuously while current flows, it is disadvantageous that the electric motor cannot be restarted until the power is turned off and cooled to a predetermined temperature or less.

The present invention has been proposed to solve the above-mentioned problems of the prior art, and an object thereof is to provide a start switch for an electric motor which can significantly reduce unnecessary power consumption after starting.

In addition, another object of the present invention is to provide a start switch for an electric motor that can shorten the restartable time of the electric motor.

Other objects and advantages in addition to the above objects and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

The start switch for an electric motor according to the first aspect of the present invention includes a rectifier circuit for rectifying an input AC power source to a pulse current source, a silicon controlled rectifier having an anode connected to a positive output terminal of the rectifier circuit and a cathode connected to a negative output terminal of the rectifier circuit. At least one voltage connected in series between a device, an anode of the silicon-controlled rectifier, and a thermistor having a self-resistance value increasing as the ambient temperature increases, and at least one voltage connected in series between the other end of the thermistor and a gate of the silicon-controlled rectifier. It includes a dropping element.

In a preferred embodiment according to the above feature, when the silicon controlled rectifier is turned on, the voltage applied to the gate of the silicon controlled rectifier is lower than the gate turn on voltage.

In addition, in another preferred embodiment according to the above features, the starter switch for the electric motor further includes a resistance element having one end connected to the gate of the silicon controlled rectifier and the other end connected to the negative output terminal of the rectifier circuit. .

In addition, in another preferred embodiment according to the above feature, the start switch for the electric motor further includes a capacitor having one end connected to the gate of the silicon controlled rectifier and the other end connected to the negative output terminal of the rectifier circuit.

Further, in another preferred embodiment according to the above feature, the silicon controlled rectifier is turned off as the resistance value of the thermistor increases above a predetermined value.

The start switch for an electric motor according to the second aspect of the present invention includes a rectifier circuit for rectifying an input AC power source to a pulse current source, and a silicon controlled rectifier having an anode connected to a positive output terminal and a cathode connected to a negative output terminal. A thermistor whose one end is connected to the anode side of the silicon controlled rectifier and whose resistance increases with increasing ambient temperature, at least one voltage drop element connected to the other end of the thermistor, from the voltage drop element And an amplifier configured to amplify the input voltage and output the amplified voltage to the gate of the silicon controlled rectifier.

In a preferred embodiment according to the above feature, when the silicon controlled rectifier is turned on, the voltage input to the amplifier is lower than the turn-on voltage of the amplifier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

2 is a view schematically showing the configuration of a start switch for an electric motor according to a first embodiment of the present invention. The starter switch 10 for the electric motor is connected to the terminals T2 and T3 in place of the PTC element 3 shown in FIG. 1, and the illustration of the motor and the AC power is omitted in this drawing.

Referring to FIG. 2, the starter switch 10 for the electric motor includes a rectifier circuit connected to power input terminals T2 and T3, that is, a bridge diode including first to fourth diodes D1, D2, D3, and D4. A silicon control rectifier (SCR) 11 having an anode connected to the positive output terminal of the bridge diode and a cathode connected to the negative output terminal, and a thermistor TH having one end connected to the anode of the SCR. ), A first resistor (R1), a fifth diode (D5), and a sixth diode (D6) sequentially connected to the other end of the thermistor, one end of which is at the cathode of the D6 and the other end of the bridge diode. A first capacitor C1 and a second resistor R2 are respectively connected to the negative output terminal of and the cathode of D6 is connected to the gate of the SCR 11.

The PTC element employed in the conventional starter switch is a kind of heater that self-heats due to the conduction current, while the thermistor TH employed in the present embodiment absorbs heat generated from adjacent elements (eg, SCR, resistance, etc.). By increasing the internal resistance, the component is smaller in size and lower in calorie value than the PTC element, so that the holding current and the holding heat are low, and the cooling rate is also high.

Here, the first resistor (R1) and the second resistor (R2) is for passing a current for stably controlling the ON / OFF of the SCR (11), the resistance value is preferably adopted to a large value Do. In addition, the D5 and D6 is a kind of voltage drop device for dropping a predetermined level of voltage (for example, by 0.65V) by an internal potential barrier.

The operation of the start switch for an electric motor having the above-described configuration is as follows.

First, the AC power input through the terminals T2 and T3 is rectified as a pulse current power by a bridge diode composed of the D1 to D4 and input to the anode and thermistor TH of the SCR 11. The graph of (a) of FIG. 3 shows the waveform of the AC power source input to the terminals T2 and T3, and (b) the graph shows the pulse wave waveform rectified by the bridge diode comprised of said D1-D4.

The voltage input to the thermistor TH is applied to the gate of the SCR 11 via the first resistor R1 and D5 and D6 to turn on the SCR 11. In this way, power is supplied to a starting coil (not shown) of the motor through the terminals T2 and T3 to operate the motor.

Strictly speaking, since an AC power supply (for example, 60 Hz) is applied to the SCR 11, the SCR 11 is turned off every time the voltage drops to '0 V' (120 times per second). Therefore, the SCR 11 supplies power to the starting coil of the motor while repeating the on / off cycle.

In addition, once the SCR 11 is turned on, the voltage between the anode and the cathode is lowered to about 1V, while the voltage dropped at D5 and D6 becomes 1.3V, and the voltage applied to the gate becomes 0.0V or less. Since this is lower than the gate turn-on voltage (0.65V) of the SCR 11, no current flows to the gate. This makes it possible to cut off the meaningless gate current while the SCR 11 is turned on.

The values of R1, C1, and R2 and the drop voltages of D5 and D6 shown in FIG. 2 are such that the voltage applied to the gate of the SCR 11 while the SCR 11 is turned on is lower than the gate turn on voltage. It is enough if designed.

When the SCR 11 is turned on and operated, the thermistor TH absorbs heat generated in an adjacent element (ie, SCR, resistor, diode, etc.), thereby increasing its own resistance due to the temperature rise. As a result, the voltage dropping in the thermistor TH is increased so that the voltage applied to the gate of the SCR 11 is decreased. After a predetermined period (approximately 0.3 to 0.8 seconds), the gate of the SCR 11 is increased. The voltage drops below the threshold voltage (0.65V). Thereafter, the SCR 11 is turned on at the timing when the voltage supplied to the anode falls to the 0V level.

Even when the SCR 11 is turned off, since the small current continues to flow through the second resistor R2 connected to the cathode of the D6, the thermistor TH receives the increased resistance due to its own micro heating. Keep constant As a result, the gate voltage of the SCR 11 is continuously maintained at a value below the threshold voltage so that the SCR 11 is kept in the off state.

Here, the time from the initial drive until the SCR 11 is completely turned off is the start time, that is, the time when power is supplied to the start winding of the electric motor.

Capacitor C1, which is an unexplained element, is employed to implement soft starting. That is, it is to prevent the shock from being applied to the electric motor by suddenly applying a high voltage during the initial driving. In initial driving, the voltage of the cathode of D6 is gradually increased while C1 is being charged, thereby supplying the electric motor with gradually increasing power.

According to this embodiment, once the SCR is turned on, the gate current of the SCR is automatically cut off due to the voltage drop in D5 and D6, thereby reducing the meaningless power consumption.

4 is a diagram schematically showing the configuration of a start switch for an electric motor according to a second embodiment of the present invention.

Referring to FIG. 4, the start switch 20 for the electric motor is a modified embodiment of the switch of FIG. 2, and its basic configuration and operation principle are similar.

Looking at a specific configuration, the start switch 20 has a bridge diode consisting of D1 to D4, an SCR 11 connected between both output terminals of the bridge diode, and an end of the anode of the SCR 11. The first resistor R1 connected to the other end, the thermistor TH, the fifth diode D5 and the third resistor R3 connected in series to the other end of the R1, and a base connected to the third resistor And the collector is connected to the npn bipolar transistor Q connected to the first resistor R1, the emitter of the transistor Q is connected to one end, and the other end to the negative output terminal of the bridge diode. One end is connected to the connected fourth resistor R4, one end of the cathode of D5 and the other end of the capacitor C1 connected to the negative output terminal of the bridge diode, and one end of the transistor Q. A second resistor R having the other end connected to the negative output terminal of the bridge diode; It includes 2).

The operating principle of the starter switch 20 for an electric motor will be described below with a focus on the differences from the first embodiment.

First, the pulse current voltage rectified and applied through the bridge diode is dropped at R1, thermistor TH, D5, and R3 and applied to the base of the transistor Q. As a result, the emitter and the collector of the transistor Q are turned on, and an amplified voltage is applied to the gate of the SCR 11 connected to the emitter terminal to turn on the SCR 11. Accordingly, power is supplied to a starting coil (not shown) of the motor through the terminals T2 and T3 to operate the motor.

As in the first embodiment, since the AC power (for example, 60 Hz) is applied to the SCR 11, whenever the voltage drops to '0 V' (120 times per second), the SCR 11 is turned off. do. Therefore, the SCR 11 supplies power to the starting coil of the motor while repeating the on / off cycle.

In addition, once the SCR 11 is turned on, the voltage between the anode and the cathode is lowered to about 1V, while the voltage applied to the base of the transistor Q due to the voltage drop caused by R1, D5, and R3 turns on the transistor. It becomes below voltage (for example, 0.65V). As a result, the transistor Q is turned off, so that the gate voltage of the SCR 11 is also lower than the turn on voltage (0.65V) so that no current flows through the gate. This makes it possible to cut off the meaningless gate current while the SCR 11 is turned on.

The values of R1, C1, R2 and R3 and the drop voltage of D5 shown in FIG. 4 are designed such that the voltage applied to the base of the transistor Q is lower than the transistor turn-on voltage when the SCR 11 is turned on. If enough.

When the SCR 11 is turned on and operated, the thermistor TH increases its own resistance due to heat generation of adjacent elements SCR, resistors, diodes, and the like, thereby being applied to the base of the transistor Q. The voltage is lowered and eventually the transistor Q is turned off. As a result, the gate voltage of the SCR drops below the threshold voltage (0.65V). Thereafter, the SCR 11 is turned on at the timing when the voltage supplied to the anode falls to the 0V level.

After the SCR 11 is turned off, the minute current continues to flow through the second resistor R2 and the microheating is thereby continued, so that the thermistor TH keeps the increased resistance value constant. Therefore, the base voltage of the transistor Q is continuously maintained below the threshold voltage so that both the transistor Q and the SCR 11 remain in the off state.

The capacitor C1 is responsible for implementing soft starting as in the first embodiment.

According to the present embodiment, since the transistor which is an amplifying element is adopted, precise control by fine current is possible, and when the SCR 11 is turned off, the current flowing through R2 is reduced than in the first embodiment, which is unnecessary. The power consumption can be further reduced.

According to the present invention, after the silicon control rectifying element (SCR) is turned on and operated when the electric motor is started, the gate current of the SCR is cut off after a predetermined time to prevent unnecessary power consumption.

In addition, since the voltage applied to the gate is lower than the gate turn on voltage once the SCR is turned on, it is possible to block the flow of meaningless gate current. This not only reduces power consumption, but also enables the adoption of an SCR having a lower rated specification by reducing the amount of conduction current.

In addition, according to the present invention, since the thermistor absorbs heat generated in an element such as an SCR or a resistor, and the self-resistance value increases above a certain level, the SCR is automatically turned off, so that an element including an SCR is overheated. It can prevent damage by

In addition, the thermistor employed in the present invention has a smaller component size and a smaller amount of self-heating than the conventional PTC device, resulting in a high cooling rate, thereby shortening the time required for restarting the electric motor.

In addition, by employing the transistor, it is possible to fine-tune the voltage applied to the gate of the SCR, in which case the power consumption can be further reduced.
In addition, the present invention uses a thermistor whose heat capacity is smaller than that of PTC as a heat resistance element for an electric motor, thereby reducing standby power consumption after operation and reducing power consumption reduced by tens of minutes due to the amplification of transistors. .

As mentioned above, although the present invention has been described with reference to the preferred embodiments, those skilled in the art will understand that changes may be made without departing from the spirit and scope of the invention. In other words, the present invention may be modified within the scope of the appended claims and should not be considered as being limited to the above-described exemplary embodiments.

Claims (13)

A rectifier circuit for rectifying the input AC power with a pulse current power supply, A silicon controlled rectifier having an anode connected to the positive output terminal of the rectifier circuit and a cathode connected to the negative output terminal of the rectifier circuit; A thermistor whose one end is connected to the anode of the silicon controlled rectifier and whose resistance increases with increasing ambient temperature; At least one voltage drop element connected in series between the other end of the thermistor and the gate of the silicon controlled rectifier; Starting switch for an electric motor comprising a. The method of claim 1, And when the silicon controlled rectifier is turned on, the voltage applied to the gate of the silicon controlled rectifier is lower than the gate turn on voltage. The method of claim 1, And a resistance element having one end connected to the gate of the silicon controlled rectifier and the other end connected to the negative output terminal of the rectifier circuit. The method of claim 3, And a capacitor having one end connected to the gate of the silicon controlled rectifier and the other end connected to the negative output terminal of the rectifier circuit. The method according to any one of claims 1 to 4, And the silicon controlled rectifier is turned off at a time when the AC input voltage is zero after the resistance value of the thermistor reaches a predetermined reference value. The method of claim 5, The voltage drop element is a starter switch for an electric motor, characterized in that the diode. The method of claim 6, The rectifier circuit is a starter switch for an electric motor, characterized in that the bridge diode. A rectifier circuit for rectifying the input AC power with a pulse current power supply, A silicon controlled rectifier having an anode connected to the positive output terminal of the rectifier circuit and a cathode connected to the negative output terminal of the rectifier circuit; A thermistor whose one end is connected to the anode side of the silicon controlled rectifier, and whose resistance increases with increasing ambient temperature; At least one voltage drop element connected to the other end of the thermistor; An amplifier for amplifying a voltage input from the voltage drop element and outputting the voltage to a gate of the silicon controlled rectifier element Starting switch for an electric motor comprising a. The method of claim 8, And when the silicon controlled rectifier is turned on, the voltage input to the amplifier is lower than the turn on voltage of the amplifier. The method of claim 8, One end is connected to the input terminal of the amplifier and the start switch for an electric motor, characterized in that it further comprises a resistor connected to the other end of the (-) output terminal of the rectifier circuit. The method of claim 10, One end is connected to the input terminal of the amplifier and the start switch for the electric motor further comprises a capacitor connected to the other end of the (-) output terminal of the rectifier circuit. The method according to any one of claims 8 to 11,  And the silicon controlled rectifier is turned off at a time when the AC input voltage is zero after the resistance value of the thermistor reaches a predetermined reference value. The method of claim 12, The amplification unit is a starter switch for an electric motor, characterized in that the transistor.

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