JPH08308272A - Single-phase induction motor for starting thyristor - Google Patents

Abstract

PURPOSE: To realize a starting circuit very simply by connecting a minute resistor end in a main winding circuit to the gate terminal of a reverse conducting thyristor in an auxiliary winding circuit provided with a capacitor. CONSTITUTION: In the case of a capacitor-start motor, a mechanical switch is replaced with a reverse conducting thyristor 3. A gate drive voltage for the thyristor 3 is a voltage generated in a minute resistor 4 inserted in the path of the main winding 1. Since the current of the main winding 1 decreases after a start, it becomes unable to turn the thyristor 3 on, and this performs the cut-off of a starting circuit. When a reverse conducting thyristor 3 having a conforming rating is not available, a substitute is made by adding double diodes to a thyristor or triac. In the case of a capacitor-start capacitor-run type, the rated voltage of the thyristor 3 is made higher. In the case of a split- phase-start motor, an auxiliary winding 2 is used as a winding in charge of a lagging magnetic field reversely to a usual case, and a mechanical switch is replaced with a triac for solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-phase induction motor.

[0002]

2. Description of the Related Art In a single-phase induction motor, a starting circuit (auxiliary winding, condenser, etc.) is disconnected by a centrifugal force switch or an electromagnetic relay after starting.

[0003]

A problem with centrifugal switches and electromagnetic relays is that they are difficult to maintain. It suffices to replace these with an AC semiconductor switching element, but for example, a triac distorts the current waveform and does not produce a starting torque.
Therefore, the semiconductor circuit for the induction machine becomes complicated and expensive. The challenge is to realize a very simple circuit.

[0004]

In a condenser starting motor, the mechanical switch is replaced by a reverse conducting thyristor. The gate drive voltage of the thyristor is a voltage of 0.7 V or more generated in the minute resistance inserted in the main winding path.
After starting, the main winding current diminishes and the thyristor cannot be turned on, which disconnects the starting circuit. If there is no compatible product of reverse conducting thyristor, build it by adding anti-parallel diode to thyristor or triac. Capacitor start In the capacitor run type, the voltage rating of the thyristor is increased.

In the split-phase starter motor, the auxiliary winding is replaced with a winding in charge of the delayed magnetic field, and the mechanical switch is replaced with a triac to solve the problem. Since the triac has the effect of delaying the AC phase, the auxiliary winding generates a lagging magnetic field to generate a starting torque. The gate of the triac is connected to the small resistor placed in the main winding as above.

Operation: The starting circuit turns on automatically when starting and turns off automatically after acceleration, and has the same function as a motor with a centrifugal force switch.

[0006]

Example 1 is shown in FIG. Replace the centrifugal switch of the 100V / 100W condenser starting motor with a triac with a diode (about 5A). Small resistance to be inserted in the main winding circuit is about 0.05Ω, thick two chrome wire 1c
m.

Example 2 100V / 100W type condenser The condenser of the starting motor is removed. Replace the centrifugal force switch with a triac (about 5A). The value of series resistance inserted in the main winding circuit is about 0.05Ω. It becomes a phase split starter motor whose rotation direction is opposite to that of the motor before modification.

[0007]

Since there is no mechanical operation or electrical contact, there is no failure, no operating noise, and no electric spark. The circuit is extremely simple and inexpensive. The motor volume is reduced by the amount of the centrifugal switch chamber.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a capacitor starting motor of the present invention.

[Explanation of symbols]

 1 Main winding 2 Auxiliary winding 3 Reverse conduction thyristor 4 Small resistance 5 Starting capacitor

Claims (2)

[Claims] 1. A starting circuit for a single-phase induction motor, which is formed by connecting a small resistance end in a main winding circuit and a gate terminal of a reverse conducting thyristor in an auxiliary winding circuit with a capacitor. 2. A starting circuit for a single-phase induction motor, which is formed by connecting a small resistance end in a main winding circuit and a gate terminal of a bidirectional thyristor in an auxiliary winding circuit.