JPH0341020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a capacitor-starting single-phase induction motor starting circuit.

Prior Art A conventional starting device for starting a single-phase induction motor, as shown in Japanese Utility Model Publication No. 39-23789, uses a main coil and an auxiliary coil connected in parallel to an alternating current voltage, and a main coil and an auxiliary coil with opposite polarities. two silicon-controlled rectifiers connected in parallel and series to the auxiliary coil so that A starting circuit consisting of a device and a device is known.

In this starting circuit, for example, one silicon-controlled rectifying element is made conductive during the positive component in one cycle, and the other silicon-controlled rectifying element is made conductive during the negative component, thereby supplying a sine wave current to the auxiliary coil and causing rotation. Efforts are being made to improve torque.

However, for single-phase induction motors used in applications where the load fluctuates widely, the alternating current flowing through the main coil, and therefore the secondary voltage of the transformer, fluctuates greatly, and one cycle does not necessarily have a positive voltage or a negative voltage. The voltages do not match. For this reason, it is not possible to obtain a gate voltage sufficient to make both silicon-controlled rectifiers conductive in one cycle, resulting in cases where only one silicon-controlled rectifier becomes conductive. That is, in the conventional circuit configuration described above, the reference voltage that makes the silicon-controlled rectifying element conductive is not the full ignition, but rather causes the current to flow from a small phase angle. Therefore, the current whose phase angle is to be controlled appears in the auxiliary coil as heat generation. Furthermore, due to the small current, it takes a long time to reach a predetermined rotational speed. Furthermore, as each phase control progresses, iron loss due to high frequency causes an increase in motor heat generation. Furthermore, for example, one silicon-controlled rectifier is made conductive by the positive component voltage of a half cycle in one cycle, but the negative component voltage of the next half cycle does not reach the gate voltage, and even if it becomes conductive, it is due to phase control. Sufficient current is not obtained to obtain starting torque, and it takes time to reach a predetermined rotational speed.

The present invention was invented to solve the above-mentioned conventional drawbacks, and its purpose is to provide a bidirectional switching element when starting the motor and returning the motor to a predetermined rotation speed. You can ensure full ignition and increase the current value of the starting coil.
Start up the motor to the specified rotation speed in a short time,
An object of the present invention is to provide a starting circuit for a single-phase induction motor that can be turned back on.

Structure of the Invention Hereinafter, the present invention will be explained according to examples. Fig. 1 is a circuit diagram showing a single-phase induction motor starting circuit according to the invention, and Figs. 2 and 3 are schematic diagrams showing operating states. This is an explanatory diagram, and in the diagram, a pulse transformer 1 has one end of its primary coil connected to a single-phase AC power source AC via a power switch 2.
One end is connected to the terminal E1 to which the main coil L1 of the single-phase induction motor is connected, and the other end is connected to the terminal E2 to which the other end of the single-phase AC power supply AC is connected via the main coil L1 of the single-phase induction motor. A voltage corresponding to the current is generated on the secondary coil side.

The secondary coil side of the pulse transformer 1 is connected to the gate of a thyristor 6 via a rectifying diode 3, a smoothing capacitor 4, and a Zener diode 5 for setting a reference voltage, and the cathode of the thyristor 6 is connected to the terminal E1. They are connected in common and the anode is connected to the gate of the triac 7.

T2 of the triax 7 is commonly connected to the terminal E1, and T1 is commonly connected to the terminal E2 via a boost capacitor 8 and a single-phase induction motor starting coil L2.

The diode 9 has a cathode connected to the triax 7.
The boosting capacitor 8 is connected in common to the gates of the boosting capacitor 8 and the starting coil L2.

In the figure, R1 to R5 are current limiting resistors.

After connecting the single-phase AC power supply AC to the terminals E1 and E2, when the power switch 2 is turned on, as shown in Figure 2, when the terminal E1 is (-) and the terminal (+), the pulse transformer is turned on. A single-phase AC power supply AC is supplied to the main coil L1 through the primary side of the pulse transformer 1, and the pulse transformer 1 is operated as a current transformer to apply a voltage corresponding to the current passing through the main coil L1 to the secondary coil side. generate.

The secondary voltage is rectified by a rectifier diode 3 and a smoothing capacitor 4, and when the rectified voltage reaches the reference voltage set by the Zener diode 5 or higher, it is applied to the gate of the thyristor 6, and the voltage is applied to the gate of the thyristor 6. At the same time, a gate voltage is applied to the gate of the triax 7 to turn on the triax 7 and charge the boost capacitor 8, and at the same time, a single-phase AC power supply AC is supplied to the starting coil L2.

As shown in Figure 3, as time progresses, the terminal E1 changes to (+) and the terminal E2 changes to (-).
The charge charged in the boosting capacitor 8 is applied to the gate of the triax 7 via the diode 9, turning on the triax 7, and transmitting the single-phase AC power supply AC voltage and the voltage of the boosting capacitor 8 to the starting coil L2. A full-ignition type voltage consisting of is supplied to the main starting coil L2, and the starting coil L
A rotating magnetic field can be obtained by excitation of 2.

Therefore, in this embodiment, when the positive voltage of a half cycle in the rectified half-wave current is equal to or higher than a predetermined reference voltage, the thyristor 6 fires from the zero point of the next non-cycle to turn on the triac 7. AC power with a full ignition waveform is supplied to the starting coil L2, and the boost capacitor 8 is charged.
By turning on
It is possible to reliably ignite the starting coil L2 and increase the current supplied to the starting coil L2. As a result, a high starting torque can be obtained, and the motor can be started up to a predetermined rotation speed and returned to a predetermined rotation speed in a short time.

As shown in FIG. 4, the present invention includes a Zener diode 10 having a potential higher than the reference voltage of the Zener diode 5, a thyristor 11 that is turned on when the potential is higher than the reference voltage set by the Zener diode 10, Even better starting characteristics can be obtained by configuring the triac 12, diode 13, and capacitor 14 in the same manner as in this embodiment, and by connecting them in parallel to the circuit of this embodiment.

Effects of the Invention As explained above, the present invention includes a main coil connected to an AC power source, a starting coil connected in parallel with the main coil, a starting capacitor connected in series with the starting coil, and a starting coil and a starting capacitor. A bidirectional switching element connected in series, a diode whose anode is connected between the starting coil and the starting capacitor and whose cathode is connected to the gate of the bidirectional switching element, and a diode whose anode is connected to the gate of the bidirectional switching element. A unidirectional switching element connected to the gate and having its cathode connected to one side of the AC power supply, a current detection member connected in series to the main coil and generating an AC current according to the current flowing through the main coil, and a current detection member. A rectifier circuit that half-wave rectifies the alternating current of the member, and a reference voltage setting member that becomes conductive and applies a voltage to the gate of the unidirectional switching element when the half-wave rectified voltage is equal to or higher than a predetermined voltage, When the half-wave rectified positive component voltage exceeds a predetermined voltage, the conducting unidirectional switching element fires the bidirectional switching element to supply AC power to the starting coil and charging the starting capacitor. , when the half-wave rectified voltage has a negative component, the bidirectional switching element is fired by the charge of the starting capacitor applied through the diode, and when starting the motor and increasing the motor to a predetermined rotation speed. When returning the motor to the specified rotation speed, we have developed a starting circuit that can fully fire the bidirectional switching elements to increase the current value of the starting coil, and can quickly bring the motor up to and return to the specified rotation speed. can be provided.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a single-phase induction motor starting circuit according to the present invention, Figs. 2 and 3 are schematic explanatory diagrams showing operating states, and Fig. 4 shows a modified embodiment of the present invention. This is a circuit diagram, in which 1 is a pulse transformer as a current detector, 6 is a thyristor as a unidirectional element, 7 is a triax as a bidirectional element, 8 is a capacitor, L1 is a main coil, and L2 is a starting coil. , AC is single-phase alternating current power supply.

Claims (1)

[Claims] 1. A main coil L1 connected to an AC power supply, a starting coil L2 connected in parallel to the main coil, a starting capacitor 8 connected in series to the starting coil, and the starting coil L2 and starting capacitor 8. A bidirectional switching element 7 connected in series, and a diode 9 whose anode is connected between the starting coil L2 and the starting capacitor 8 and whose cathode is connected to the gate of the bidirectional switching element 7.
A unidirectional switching element 6 whose anode is connected to the gate of the bidirectional switching element 7 and whose cathode is connected to one side of the AC power supply is connected in series to the main coil L1, and the current flowing through the main coil L1 A pulse transformer 1 that generates a corresponding alternating current, a diode 3 and a smoothing capacitor 4 that half-wave rectify the alternating current generated on the secondary side of the pulse transformer 1, and resistors R2 and R3 connected in series. , a tweed diode 5 that becomes conductive and applies a gate voltage to the gate of the unidirectional switching element 6 when the half-wave rectified voltage is equal to or higher than a predetermined voltage set by the resistors R2 and R3; When the wave-rectified positive component voltage exceeds a predetermined voltage, the conductive unidirectional switching element 6 ignites the bidirectional switching element 7 and activates the starting coil L2.
When the half-wave rectified voltage has a negative component, the bidirectional switching element 7 is ignited by the charge of the starting capacitor 8 applied via the diode 9. A starting circuit characterized in that: