JPH04299083A - Motor start control circuit - Google Patents

Abstract

PURPOSE:To enhance reliability in start control of motor and to realize downsizing and noise suppression. CONSTITUTION:Upon turn ON of power, AC current is fed to the main winding (L1) of a motor (10). The AC current is rectified through a bridge rectifying circuit (BG) and a thyristor (SCR) is turned ON according to the rectified output and thereby a triac (TR) is turned ON to feed an AC current to an auxiliary winding (L2). At the same time, a capacitor (Cc) in a time constant circuit (TC) is charged according to the rectified output from the bridge rectifying circuit (BG). When the potential of the capacitor (Cc) reaches a predetermined level, a transistor (Q1) is turned ON and thereby the thyristor (SCR) is turned OFF while the triac (TR) is turned OFF. Consequently, current flowing through the auxiliary winding (L2) is interrupted thus finishing the starting operation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor starting control circuit for controlling the current flowing through an auxiliary winding or a starting capacitor when starting, for example, a single-phase motor.

0002

2. Description of the Related Art FIG. 3 shows a conventional split-phase starting type motor starting control circuit, and FIG. 4 shows a capacitor starting type motor starting control circuit. That is, Figure 3
In the split-phase starting type shown in FIG. In the capacitor starting type shown in , a series circuit of an auxiliary winding L2, a centrifugal force switch SW, and a starting capacitor C is connected in parallel to a main winding L1 of a single-phase motor M having a squirrel cage rotor RT. As is well known, the centrifugal force switch SW has switch contacts that are opened and closed according to the rotational speed of a single-phase motor. That is, when the rotational speed of the motor is, for example, 70% or less of the synchronous speed, the contact remains closed, and when the rotational speed of the motor exceeds 70%, the switch contact is opened due to centrifugal force.

0003

[Problems to be Solved by the Invention] However, the startup control circuit using the conventional centrifugal force switch SW described above is not operated due to wear of the switch contacts or foreign matter getting into the mechanical part that opens and closes the switch contacts by centrifugal force. A defect may occur and the motor may fail to start. Since this startup failure can lead to serious accidents such as motor winding burnout, it is desired to improve the reliability of the startup control circuit. In addition, the conventional startup control circuit is
Since a mechanical centrifugal force switch SW is used, there is a limit to miniaturization, and there is also a problem in that noise is generated when the switch contacts open and close.

[0004] This invention was made to solve the above-mentioned problems, and its purpose is to provide a motor that can improve the reliability of starting control, is small and can prevent the generation of noise. The present invention attempts to provide a start-up control circuit.

[0005]

[Means for solving the problem] That is, this invention
In order to solve the above problem, a first switch element is connected between a main winding and an auxiliary winding of a motor, and supplies an alternating current to the auxiliary winding when power is turned on; a rectifier circuit that is provided between one end of the passage and the control signal input terminal and that rectifies the alternating current; a second switch element that is turned on in response to the rectified output of the rectifier circuit; a time constant circuit that is charged by the time constant circuit; and a third circuit that is made conductive when the charging potential of the time constant circuit reaches a predetermined value, and that makes the second switch element non-conductive and the first switch element non-conductive. A switch element is provided. The first switch element is constituted by a triac. The second switch element is constituted by a thyristor.

[0006]

According to the present invention, when the power is turned on, alternating current is supplied to the main winding, and at the same time, the first switch element is turned on and alternating current is supplied to the auxiliary winding. At the same time, the alternating current is rectified by the rectifier circuit, and the second switch element is made conductive in accordance with the rectified output. The time constant circuit is charged according to the rectified output, and when this charging potential reaches a predetermined value, the third switching element is turned on. In response to the conduction of the third switch element, the second switch element becomes non-conductive, the current flowing through the rectifier circuit decreases, the first switch element becomes non-conductive, the auxiliary winding is disconnected, and the startup is started. is completed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a single-phase motor 10 includes a squirrel cage rotor RT, a main winding L1, an auxiliary winding L2, and a connecting terminal 1.
1 to 14 are provided. Both ends of the main winding L1 are connected to connection terminals 11 and 12, and both ends of the auxiliary winding L2 are connected to connection terminals 11 and 13. In addition, connection terminal 1
1 and 12 are connected to a power source via a power switch (not shown), and connection terminals 12 and 14 are directly connected.

[0009] The connection terminals 14 and 13 are connected to a first switching element, for example, T1 and T2 terminals of a triac TR, and a resistor Rs constituting a snubber circuit.
, a series circuit of capacitors Cs is connected. A resistor R1 is provided between the T1 terminal of the triac TR and the gate G to prevent malfunction of the triac TR.
A capacitor C1 is connected in parallel.

[0010] The T2 terminal and gate G of the triac TR are each connected to the input end of a bridge rectifier circuit BG. The output terminals of this bridge rectifier circuit BG are respectively connected to the anode A and cathode K of a second switch element, for example a thyristor SCR. A capacitor C2 is connected between the gate G and cathode K of this thyristor SCR, as well as the collector and emitter of a third switching element, such as a transistor Q1. This transistor Q1 is a thyristor SCR
The collector is connected to the anode A of the thyristor SCR via a resistor R2. Further, a resistor Rc and a capacitor Cc are connected in series between the anode A and the cathode K of the thyristor SCR. These resistor Rc and capacitor Cc are the thyristor S
A time constant circuit TC is configured to set the timing of extinguishing the arc of CR, and a connection point between the resistor Rc and the capacitor Cc is connected to the base of the transistor Q1. The time constant of the time constant circuit TC is set to the time required for the rotational speed of the motor 10 to reach, for example, 70% of the synchronous speed. Further, the capacitor Cc includes a resistor R3.
are connected in parallel. In the above configuration, the operation will be explained.

When a power switch (not shown) is turned on, AC voltage is supplied to the main winding L1 via the connection terminals 11 and 12 of the motor 10. Further, the AC voltage supplied from the connection terminals 11 and 12 is supplied to the bridge rectifier circuit BG via the auxiliary winding L2 and the resistor R1. The rectified output of this bridge rectifier circuit BG is supplied to the gate G of thyristor SCR via resistor R2, and this thyristor SCR is turned on. Along with this, bridge rectifier circuit BG
A current flows from the gate G to the gate G of the triac TR, and the triac TR is turned on. Therefore, as shown in FIG. 2, AC voltage is supplied to the auxiliary winding L2, and the squirrel cage rotor RT is rotated.

On the other hand, the rectified output of the bridge rectifier circuit BG is charged to a capacitor Cc via a resistor Rc. The potential across capacitor Cc rises according to the above-described time constant, and when it reaches a predetermined potential, transistor Q1 becomes conductive. Therefore, the potentials of the collector and emitter of transistor Q1 become lower than the gate trigger voltage of thyristor SCR, and thyristor SCR is turned off. As a result, the current flowing through the bridge rectifier circuit BG decreases, and the gate voltage of the triac TR connected to the input terminal of the bridge rectifier circuit BG decreases. Therefore, the triac TR is turned off, and as shown in FIG. 2, the current in the auxiliary winding L2 is cut off, and the startup is completed.

According to the above embodiment, the same function as a conventional centrifugal force switch is realized by the triac TR and the control circuit of this triac TR. Therefore, since it does not have mechanical parts unlike conventional models, it is possible to improve operational reliability, make it more compact, and prevent the generation of noise during operation. be.

[0014] In the above embodiment, a split-phase start type motor start control circuit has been described, but the present invention is not limited to this. It is also possible to apply

Further, in the above embodiment, a triac was used as the first switching element, a thyristor was used as the second switching element, and a transistor was used as the third switching element, but the present invention is not limited to this. It is also possible to use other switching elements. It goes without saying that various other modifications can be made without departing from the gist of the invention.

[0016]

[Effects of the Invention] As detailed above, according to the present invention,
It is possible to provide a motor start control circuit that can improve the reliability of start control, is compact, and can prevent noise generation.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing currents in a main winding L1 and an auxiliary winding L2 shown in FIG. 1.

FIG. 3 is a configuration diagram showing a conventional motor starting control circuit.

FIG. 4 is a configuration diagram showing a conventional motor starting control circuit.

[Explanation of symbols]

10...Motor, L1...Main winding, L2...Auxiliary winding, TR...
Triac, SCR...thyristor, BG...bridge rectifier circuit, Q1...transistor, TC...time constant circuit.

Claims (3)

[Claims] 1. A first switch element connected between a main winding and an auxiliary winding of a motor and supplying an alternating current to the auxiliary winding when power is turned on; and a current path of the first switch element. a rectifier circuit that is provided between one end and a control signal input terminal and that rectifies the alternating current; a second switch element that is made conductive according to the rectified output of the rectifier circuit; a time constant circuit, and a third switch element that becomes conductive when the charging potential of the time constant circuit reaches a predetermined value, makes the second switch element non-conductive, and makes the first switch element non-conductive. A motor starting control circuit comprising: 2. The motor starting control circuit according to claim 1, wherein the first switch element is a triac. 3. A starting control circuit for a single-phase motor, wherein the second switch element is a thyristor.