JP3361952B2 - Motor starter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starting device for smoothly starting an electric motor by controlling the phase of a voltage applied to the electric motor from an AC power source at the time of starting the electric motor. The present invention relates to a device suitable as a starting device for a child motor.

[0002]

2. Description of the Related Art Commutator motors for both alternating and direct use are used in electric tools. An inrush current flows through the commutator motor when it is started. In particular, the power consumption exceeding 1 kW has a large inrush current, and this inrush current causes a large voltage drop in another load connected to the same power supply system as the power tool.

Therefore, conventionally, for example, a circuit shown in FIG. 3 has been proposed as a circuit for preventing the influence of the inrush current. In this case, when the switch 60 is turned on,
The alternating current supplied from the alternating-current power supply 61 to the load 62 is bypassed to the electric path 63 through the resistor R20, and this bypassed bypass current is rectified by the diode bridge D6. Then, the rectified current charges the electrolytic capacitor C20, and the electrolytic capacitor C2 is charged.
When the charging of 0 is completed, the bypass current stops flowing,
The AC current supplied from the AC power supply 61 to the load 62 passes through the resistors R20 and R21 to charge the capacitor C10.

When the voltage across the capacitor C10 reaches the switching voltage of the trigger diode D5,
The trigger diode D5 is turned on, the triac Q6 is turned on, and a voltage is applied to the load 62. After that, the switching phase of the trigger diode D5 settles to a value determined by the charging time constants of the resistors R20, R21 and the capacitor C10, and the load 62 is driven steadily.

[0005]

By the way, in a commutator motor used for an electric power tool consuming a large amount of power, in order to solve the above-mentioned problems, a so-called smooth transition from startup to a steady operation state is required over several seconds. A soft start is required. In addition, since electric power tools are often started and stopped during use, even in such a case, it is meaningless unless soft start is possible. Therefore, considering the case where the above-mentioned conventional one is used as a starter device for a commutator motor of an electric tool, the time when the bypass current is bypassed is the electrolytic capacitor C20.
Since it is determined by the charging time, the electrolytic capacitor C20 has a capacitance (for example, 3
3 μF) must be selected.

However, when the electrolytic capacitor C20 has not finished discharging, the charging current of the capacitor C10 cannot be bypassed. Therefore, when the switch 60 is turned off and then turned on again, a soft start is performed. It is necessary to discharge the electrolytic capacitor C20 between the time when is turned off and the time when it is turned on again. In order to shorten the discharge time, it is necessary to reduce the resistance value of the resistor R23 (for example, 200 KΩ).
When the resistance value of 23 is reduced, the bypass current flows even in the steady operation state, so that the voltage applied to the commutator motor decreases, and the rotation speed of the commutator motor decreases. In other words, in a short cycle, open the switch
However, if the soft start can be performed even if it is turned on again, there is a problem that the commutator motor cannot generate the rated speed. Further, since the capacitor having a large capacitance has a large outer shape, there is a problem that the mounting space for the starting device becomes large.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and is a case where the electric motor can generate a rated speed and the electric motor is repeatedly started and stopped in a short cycle. Also aims to realize an electric motor starter capable of performing a soft start.

[0008]

In order to achieve the above object, the present invention provides a phase control means for controlling the phase of a voltage applied to an electric motor from an AC power source, and the phase control means according to the first aspect of the invention. In an electric motor starter provided with phase delay means for delaying the phase controlled by the phase control means by bypassing the current input to the control means, the phase control means includes the AC power supply from the AC power supply. While rectifying the current supplied to the electric motor, a semiconductor control element that conducts by inputting a trigger current to the gate,
A trigger element that outputs the trigger current to the semiconductor control element and a first capacitor that controls the output timing of the trigger current output from the trigger element are provided, and the phase delay means includes the first delay element. The bypass electric circuit which bypasses the charging current to the capacitor of No. 1 and the bypass electric current bypassed by this bypass electric circuit are inputted.
It turns on and the input bypass power
A transistor for outputting the flow, out of the said transistor
Bei a second capacitor is charged by the base current to be force, and a discharge circuit for discharging the second capacitor
And the transistor is the second capacitor
As the charging progresses, the base current decreases and turns off,
The technical means that the bypass current stops flowing in the bypass circuit is adopted.

Further, in the invention described in claim 2, in the starting device for the electric motor according to the first aspect, the discharge circuit is provided with the second electric current when the electric current is supplied from the AC power supply to the electric motor. The technical means of prohibiting the discharge of the capacitor and discharging the second capacitor when the supply of the current is stopped is adopted.

[0010]

In the invention described in claim 1 or 2, the charging current to the first capacitor is bypassed by the bypass circuit, and the bypass current bypassed is
It is input to the transistor . Thus, the base current of the transistor <br/> flows, the transistor is turned ON, the tiger
The bypass current is output from the transistor . Also, the base current starts charging the second capacitor. That is, since the second capacitor is charged by the base current output from the transistor, the charging time can be lengthened even if the capacitance is small.

When the charging of the second capacitor proceeds, the base current decreases and the transistor turns off. As a result, the bypass current does not flow in the bypass circuit, the charging time of the first capacitor is shortened, and the phase of the voltage applied to the electric motor is controlled by the time constant set by the first capacitor or the like. Is in steady operation. Further, the second capacitor is discharged by the discharging circuit. In this case, since the second capacitor has a small electrostatic capacity, the discharge time can be shortened.
That is, the soft start can be performed even when the start and stop of the electric motor are repeated in a short cycle. Further, since the outer shape of the second capacitor is small, the mounting space for the starter can be reduced. .

In particular, according to the second aspect of the invention, since the discharge circuit inhibits the discharge of the second capacitor when the electric current is supplied from the AC power source to the electric motor, the electric motor is in steady operation. It is possible to prevent the generation of the bypass current due to the discharge resistance of the second capacitor, eliminate the loss of the voltage applied to the electric motor, and efficiently operate the electric motor. Moreover, since the discharge circuit discharges the second capacitor when the supply of current is stopped, when the start switch of the electric motor is turned off, the second capacitor can be discharged to perform a soft start again. it can.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a motor starting device (hereinafter, simply referred to as a starting device) according to the present invention will be described below with reference to FIG. FIG. 1 is a circuit diagram showing the main configuration of the activation device according to the first embodiment. In each of the following embodiments, a starter for an AC commutator motor (hereinafter abbreviated as a motor) used for an electric power tool will be described as a representative.

First, the main structure of the starting device will be described. The starting device 10 includes a switch 14 for starting and stopping the motor 12, and a triac Q1 which is a semiconductor control element for controlling the AC voltage supplied from the AC power supply 13.
A trigger circuit 20 that outputs a trigger current to the gate of the triac Q1, a bypass circuit 30 that bypasses the charging current to the capacitor C3 provided in the trigger circuit 20, and a bypass circuit 30 that bypasses the current. Delay circuit 40 for controlling the time in which
And a discharge circuit 50 that discharges the electrolytic capacitor C1 provided at 0.

Next, the operation of the starting device 10 will be described. When the person using the electric power tool turns on the switch 14, most of the alternating current supplied from the alternating current power source 13 is bypassed by the bypass circuit 31 through the resistor R1.
A part charges the capacitor C3, which is the first capacitor, through the resistor R2. The bypassed bypass current is rectified by the diode bridge D1, and the rectified current is input to the emitter of the transistor Q2. As a result, the base current of the transistor Q2 flows, and this base current charges the electrolytic capacitor C1, which is the second capacitor, through the resistors R4, R5 and the diode D3. Further, the transistor Q2 is turned on due to the flow of the base current, and the DC current input to the emitter is amplified, output from the collector, and then flows to the resistor R6.

On the other hand, when the voltage across the capacitor C3 reaches the operating voltage of the trigger diode D2, which is the trigger element, due to the charging of the capacitor C3, the trigger diode D
A trigger current is output from 2 to the gate of the triac Q1, and the triac Q1 is turned on. This triac Q
When 1 is turned on, a voltage is applied to the motor 12 and the motor 12 starts rotating. In this case, since the charging current flowing through the capacitor C3 is small, the charging time of the capacitor C3 is long, and the firing angle of the trigger diode D2 is small. Therefore, the average voltage of the voltage applied from the triac Q1 to the motor 12 is small, and the motor 12 rotates slowly.

As the charging of the electrolytic capacitor C1 progresses, the base current of the transistor Q2 decreases and the bypass current decreases, so that the current charging the capacitor C3 through the resistor R2 increases. As a result, the charging time of the capacitor C3 is shortened and the firing angle of the trigger diode D2 is increased, so that the average voltage of the voltage applied from the triac Q1 to the motor 12 is increased and the rotation speed of the motor 12 is increased.

When the base current of the transistor Q2 becomes small, the transistor Q2 is turned off, the bypass current does not flow in the bypass circuit 31, and the alternating current passing through the resistor R1 charges the capacitor C3 through the resistor R2. As a result, the firing angle of the trigger diode D2 settles to a value determined by the charging time constants of the resistors R1, R2, and C3, and the motor 12 operates steadily. Further, since the base current flows through the transistor Q4 through the resistor R10 and the transistor Q4 is turned on, the cathode potential of the diode D4 becomes higher than the base potential of the transistor Q3. As a result, the transistor Q3 is turned off and the discharge of the electrolytic capacitor C1 is blocked. Therefore, it is possible to prevent the generation of the bypass current due to the discharge resistance of the electrolytic capacitor C1 during the steady operation of the motor 12 and to operate the motor 12 efficiently.

Next, when the switch 14 is turned off, the electrolytic capacitor C2 is discharged through the transistor Q4, the resistor R8 and the resistor R10. As a result, the base current of the transistor Q4 decreases, and the transistor Q4 becomes OF
Therefore, the cathode potential of the diode D4 decreases,
The discharge current of the electrolytic capacitor C1 flows through the transistor Q3, the diode D4 and the resistor R8. Then, the transistor Q3 is turned on, and the electrolytic capacitor C1 is discharged through the transistor Q3 and the resistor R7. That is,
By turning off the switch 14, the electrolytic capacitor C1 can be discharged.

In the first embodiment, the capacitance of the electrolytic capacitor C1 is 3.3 μF, which is one order smaller than that of the conventional electrolytic capacitor C20 (33 μF). Is discharged. That is, even when the OFF and ON cycles of the switch 14 are short, the electrolytic capacitor C1 is placed between the OFF and ON cycles.
Of the capacitor C
Since the charging current to 3 can be bypassed to the bypass circuit 31, the soft start can be performed again.

In the first embodiment, the electrolytic capacitor C2 has a capacitance of 1 μF, and the capacitor C3 has a capacitance of 0.1 μF. Further, the resistance values of the resistors R1 to R10 are 56 KΩ and 18 K, respectively.
Ω, 470KΩ, 10KΩ, 220KΩ, 1KΩ, 47
KΩ, 2.2 MΩ, 470 KΩ and 2.2 MΩ, and the transistors Q2 to Q4 are 2SA10.
15 (manufactured by Toshiba). Then, according to the experiments by the present inventors, the starting device 10 using the element having the above value is used as the input voltage 2
When used for the motor 12 of 30 V and power consumption of 2 KW, the time from the start of the motor 12 to the transition to the steady operation state, that is, the time required for the soft start was about 3 seconds. Further, even when the switch 14 was turned off and turned on again during the steady operation, the soft start could be performed again for about 3 seconds.

As described above, according to the starting device 10 of the first embodiment, as the charging current of the electrolytic capacitor C1,
Since the base current of the transistor Q2 is used, soft start can be performed in a long time even if the capacitance of the electrolytic capacitor C1 is small. Moreover, even when the switch 14 is repeatedly turned on and off in a short cycle, the capacitance of the electrolytic capacitor C1 is small and can be discharged between OFF and ON. Can also do a soft start. further,
Since the outer shape of the electrolytic capacitor C1 can be reduced, the mounting space for the starting device 10 can be reduced.

Next, a starting device according to the second embodiment of the present invention will be described with reference to FIG. 2 showing the main circuit configuration thereof. The activation device of the second embodiment is characterized in that the configuration of the delay circuit 40 and the discharge circuit 50 in the activation device of the first embodiment can be simplified and the manufacturing cost of the activation device 10 can be reduced. Since the trigger circuit 20 and the bypass circuit 30 have the same configurations as those in the first embodiment, the description thereof will be omitted.

As shown in FIG. 2, the delay circuit 70 has a diode D7 whose anode is connected to the base of a transistor Q2 provided in the bypass circuit 30. A resistor R14 is connected to the cathode of the diode D7, and the positive electrode of the electrolytic capacitor C4 is connected to the resistor R14. That is, the delay circuit 70 has a simpler configuration than the delay circuit 40 of the first embodiment, without using the two resistors R3 and R4.

The discharge circuit 80 also has a transistor Q3 whose emitter is connected between the resistor R14 and the positive pole of the electrolytic capacitor C4. The anode of the diode D8 is connected to the base of the transistor Q3, and the resistor R15 is connected to the collector. Further, the discharging circuit 80 has an electrolytic capacitor C5 charged by a bypass current, and a resistor R16 is connected in parallel to the electrolytic capacitor C5. That is, the discharge circuit 80 has a higher power consumption than the discharge circuit 50 of the first embodiment.
It has a simple configuration without using the transistor Q4 and the resistors R8 and R10.

Next, the operation of the starting device 10 will be described. When the switch 14 is turned on, most of the alternating current supplied from the alternating-current power supply 13 is bypassed by the bypass circuit 31 through the resistor R11, and a part thereof charges the capacitor C6 through the resistor R12. The bypassed bypass current is rectified by the diode bridge D1, and the rectified current is input to the emitter of the transistor Q2. This causes the base current of the transistor Q2 to flow, which charges the electrolytic capacitor C4 through the diode D7 and the resistor R14.
In addition, since the base current flows, the transistor Q2
Is turned on, the current input to the emitter is amplified, output from the collector, and then flows to the resistor R13.

On the other hand, when the voltage across the capacitor C6 reaches the operating voltage of the trigger diode D2 due to the charging of the capacitor C6, a trigger current is output from the trigger diode D2 to the gate of the triac Q1 and the triac Q1 is turned on. When the triac Q1 is turned on, a voltage is applied to the motor 12 and the motor 12 starts rotating. In this case, since the charging time of the capacitor C6 is long, the firing angle of the trigger diode D2 is small. Therefore, the average voltage of the voltage applied from the triac Q1 to the motor 12 is small, and the motor 12 rotates slowly.

Then, as the charging of the electrolytic capacitor C4 progresses, the base current of the transistor Q2 decreases and the bypass current decreases, so that the current charging the capacitor C6 through the resistor R12 increases. As a result, the charging time of the capacitor C6 is shortened, and the trigger diode D2
Since the firing angle of is increased, the average voltage of the voltage applied from the triac Q1 to the motor 12 is increased, and the rotation speed of the motor 12 is increased.

When the base current of the transistor Q2 becomes small, the transistor Q2 is turned off, the bypass current does not flow in the bypass circuit 31, and the alternating current passing through the resistor R11 passes through the resistor R12 and the capacitor C6.
To charge. As a result, the firing angle of the trigger diode D2 settles to a value determined by the charging time constants of the resistors R11, R12, and the capacitor C6, and the motor 12 operates steadily. Further, the electrolytic capacitor C5 is charged by the current rectified by the diode bridge D1, and the potential across the electrolytic capacitor C5 (for example, 34 V).
Is the emitter potential of the transistor Q3 (for example, 33
V), the transistor Q3 remains off and the electrolytic capacitor C4 is prevented from discharging. Therefore, it is possible to prevent the generation of the bypass current due to the discharge resistance of the electrolytic capacitor C4 during the steady operation of the motor 12 and operate the motor 12 efficiently.

Next, when the switch 14 is turned off, the electrolytic capacitor C5 is discharged through the resistor R16. As a result, the potential across the electrolytic capacitor C5 becomes smaller than the emitter potential of the transistor Q3, so that the transistor Q3 is turned on, the discharge current of the electrolytic capacitor C4 flows from the emitter of the transistor Q3 to the resistor R15, and the electrolytic capacitor C4 rapidly. Is discharged. As a result, even if the OFF and ON cycles of the switch 14 are short, the charging current to the capacitor C6 can be bypassed to the bypass circuit 31, so that the soft start can be performed again.

In the second embodiment, the electrostatic capacitances of the electrolytic capacitors C4 and C5 are each 0.33 μm.
F, 0.1 μF, and the capacitance of the capacitor C6 is
It is 0.1 μF. Also, the resistors R11 to R16
Resistance values are 56KΩ, 39KΩ and 2.7KΩ, respectively.
Ω, 2.7 KΩ, 1 KΩ, 470 KΩ. And
The inventors of the present invention conducted an experiment on the starting device 10 of the second embodiment under the same conditions as the first embodiment, and found that the motor 12
It took about 3 seconds from the start-up to the steady-state operation, that is, the time required for the soft start. Further, even when the switch 14 was turned off and turned on again during the steady operation, the soft start could be performed again for about 3 seconds.

As described above, according to the activation device 10 of the second embodiment, as in the first embodiment, soft start can be performed for a long time, and ON / OFF is repeated in a short cycle. Even in this case, the soft start can be performed again. Moreover, since the number of elements forming the circuit is smaller than that of the starting device 10 of the first embodiment, the reliability of the starting device 10 can be improved, and the manufacturing time can be shortened and the manufacturing cost can be reduced. be able to. Furthermore, since the outer shape of the electrolytic capacitor C 4 can be reduced, the mounting space for the starting device 10 can be reduced.

In each of the above embodiments, the time required for the soft start is the electrolytic capacitor C1 or
The capacitance value of the electrolytic capacitor C4 can be increased by increasing the capacitance value of the electrolytic capacitor C4 or decreasing the base current value of the transistor Q2. Conversely, the capacitance value of the electrolytic capacitor C1 or the electrolytic capacitor C4 can be increased. It can be shortened by reducing the value or increasing the base current value of the transistor Q2.

[0034]

As described above, according to the starting device of the present invention, the electric motor can generate the rated speed, and the soft start can be performed even when the electric motor is repeatedly started and stopped in a short cycle. It is possible to realize an electric motor starter that can be operated.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a main configuration of a starting device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a main configuration of a starting device according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram for preventing a conventional inrush current.

[Explanation of symbols]

10 Starter 20 Trigger circuit 30 Bypass circuit 40,70 delay circuit 50,80 discharge circuit C1, C4 electrolytic capacitors D2 trigger diode Q1 TRIAC Q2 transistor

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 1/42 H02P 7/622 H02P 7/635

Claims (2)

(57) [Claims] 1. A phase control means for controlling a phase of a voltage applied to an electric motor from an AC power source, and a phase controlled by the phase control means is delayed by bypassing a current input to the phase control means. In the starting device of the electric motor provided with a phase delaying unit, the phase control unit rectifies a current supplied from the AC power supply to the electric motor, and inputs a trigger current to a gate to conduct a semiconductor control. An element, a trigger element that outputs the trigger current to the semiconductor control element, and a first capacitor that controls the output timing of the trigger current output from the trigger element are provided, and the phase delay means is provided. A bypass circuit for bypassing the charging current to the first capacitor, and a bypass bypassed by this bypass circuit. As well as ON by inputting the flow, bar was the input
A transistor that outputs an bypass current, a second capacitor that is charged by a base current that is output from the transistor, and a discharge circuit that discharges the second capacitor are provided.
And the transistor is charging the second capacitor.
Then, the base current decreases and turns off, and
A starting device for an electric motor , wherein the bypass current does not flow in the electric circuit . 2. The discharging circuit inhibits discharging of the second capacitor when current is supplied from the AC power supply to the electric motor, and
The starting device for the electric motor according to claim 1, wherein the second capacitor is discharged when the supply of the current is stopped.