JPS6227035Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an improvement of a non-contact starting switch for a single-phase induction motor using a semiconductor switch, and by adding a timer such as a CR timer circuit to the control circuit of the semiconductor switch. This protects the semiconductor switch.

As an example of this type of non-contact starting switch, the one shown in FIG. 1 has already been proposed.

In Figure 1, 1 is a single-phase power supply, 2 is a power switch, 3, 4, and 5 are the rotor, main winding, and starting winding of a single-phase induction motor, 6 is a diode, 7 is a smoothing capacitor, and 8 is a smoothing capacitor. Chener diode, 9
14 is a photocoupler, 14 is an amplifier, 15 is a charging capacitor, 17 is a variable resistor, 19 is a first semiconductor switch, 20 is a rectifier, 21 is a trigger element, 2
3 is a second semiconductor switch.

Next, the operation will be explained. A slit-shaped disk (not shown) is attached to the rotor 3, and the slit portion is configured to pass or block light reaching the phototransistor from the light emitting diode of the photointerrupter 9. At the same time when the rotor 3 starts rotating, a pulse voltage proportional to the rotation speed of the rotor is generated at the output terminal of the photocoupler 9, and the capacitor 15 is charged.

When the rotation of the rotor 3 increases and the charging voltage increases and exceeds the voltage divided by the variable resistor 17, the amplifier 14'
A voltage is generated on the output side of the first semiconductor switch 1.
9 becomes conductive and at the same time the second semiconductor switch 23 becomes non-conductive, the auxiliary winding current flows through the resistor 24 and the rectifier 2.
0. Since the auxiliary winding current passes through the first semiconductor switch 19 and is suppressed to several mA by the resistor 24, the auxiliary winding circuit becomes substantially equivalent to being disconnected from the power supply.

The process in which the auxiliary winding circuit is disconnected from the power supply has been described above, and next, the time when the motor is started will be described. After switch 2 is turned on, variable resistor 1
No voltage is applied between the base and emitter of the first semiconductor switch 19, and the first semiconductor switch is non-conductive until the rotational speed reaches such that the charged voltage of the capacitor 15 reaches a voltage equal to or higher than the divided voltage of the first semiconductor switch 19. Therefore, when a voltage is applied to the capacitor 22 and the charging voltage reaches the conduction voltage of the trigger element 21 or higher, the discharge current of the capacitor becomes the gate current of the second semiconductor switch, and the second semiconductor switch becomes conductive and the starting winding is turned on. Starting current flows through 5, and the motor starts.
To accelerate. The operation when the starting winding current is cut off after reaching a sufficient rotational speed is as described above.

In the single-phase induction motor starting device configured as described above, since the starting winding current flows through the second semiconductor switch 23, if the inertia of the motor load is greater than the allowable value and the starting time is too long, or If the rotor is restrained for some reason, current may flow to the second semiconductor switch 23 beyond the permissible energization time, causing a malfunction such as destruction of the element.
Assuming the above conditions, it is necessary to take measures such as increasing the current capacity of the switch 23, paying special consideration to the heat dissipation of the switch, or adding a protective device such as a thermal protector. It has disadvantages such as being large and expensive.

The present invention has been made to eliminate the drawbacks of the conventional device described above, and provides a simple and inexpensive protection device for the second semiconductor switch by simply adding a timer circuit to the control circuit of the first semiconductor switch 19. It is something to do.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2a is a circuit diagram of a protection device according to an embodiment of the present invention. FIG. 2b is an explanatory diagram illustrating the operation of the above circuit. Terminals 32, 33, 34 in Figure 2 a
are connected to 25, 26, and 27, respectively, in FIG. The voltage at the terminal 36 becomes a constant voltage determined by the voltage division ratio of the resistors 30 and 31, while the voltage at the terminal 35 attenuates over time and reaches the voltage shown in FIG. 2b, respectively.
_R and _Vc , the output of the amplifier 14' is zero from the time the switch 2 is turned on until time t, and reaches the voltage value due to the Chener diode 8 at the moment time t passes. Therefore, even when the motor is locked, the first semiconductor switch 19 becomes conductive even if the voltage of the capacitor 15 does not rise after time t, and the second
Since the current flowing through the second semiconductor switch 23 is cut off, the capacity of the second semiconductor switch can be rationally selected depending on the starting winding current value and the allowable locking time or allowable acceleration time. On the other hand, the time t can be arbitrarily determined by selecting the capacitances of the resistors 29 to 31 or the capacitor 28, so that it can be easily adapted to the characteristics of the motor, etc., so that it is a simple, inexpensive, and versatile compensation device.

Note that the terminal 34 in the figure is located at another location, for example, at 27'.
It is clear that the same effect can be obtained by connecting the It is also clear that the resistor or capacitor of FIG. 2a can be made variable to accommodate different models.

As explained above, the starting device for a single-phase induction motor according to this invention can protect the semiconductor switch of the starting circuit at a very low cost by adding a timer circuit, and the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional device, and FIGS. 2a and 2b are circuit diagrams and characteristics explanatory diagrams of an embodiment of the present invention. In the figures, the same symbols indicate the same or corresponding parts, 1 is the power supply, 2 is the switch, 3, 4, and 5 are the rotor, main winding, and starting winding of the motor, 6 is the diode,
8 is a Chener diode, 9 is a photocoupler, 1
4 is an amplifier, 15 is a capacitor, 17 is a variable resistor, 19 is a first semiconductor switch, 20 is a rectifier, 21 is a trigger element, and 23 is a second semiconductor switch.

Claims (1)

[Claims for Utility Model Registration] (1) A photocoupler having a starting winding and consisting of a light emitting element and a light receiving element, passing through a gap between the light emitting element and the light receiving element of this photocoupler, A rotating disk fixed to the rotating shaft of the single-phase induction motor, which has a slit that blocks and passes light to provide a light pulse proportional to the rotational speed of the single-phase induction motor, and an output electrical signal from the photocoupler. a control circuit having a function of converting the amount into an amount dependent on the rotational speed of the rotating disk, a first semiconductor switch and a rectifier operated by the output signal of this control circuit, and a signal from the first semiconductor switch. In the single-phase induction motor equipped with a second semiconductor switch that disconnects the starting winding, after a predetermined period of time has elapsed after power is applied to the single-phase induction motor, the first semiconductor switch is activated and the first semiconductor switch is activated. 1. A starting device for a single-phase induction motor, characterized by comprising a timer circuit that shuts off the semiconductor switch No. 2. (2) The starting device for a single-phase induction motor according to claim 1, wherein the photocoupler comprises a light-emitting element made of a light-emitting diode and a light-receiving element made of a phototransistor. (3) The starting device for a single-phase induction motor according to claim 1 or 2, wherein the timer circuit and the control circuit operate independently.