JPH0469075A - Start and driving circuit for single phase motor - Google Patents

Abstract

PURPOSE: To start and drive a motor inexpensively without causing any damage on the motor and without complicating the system by disposing a starting capacitor, a driving capacitor and a unit for switching the starting capacitor on/off in the same case which can be coupled with the motor. CONSTITUTION: A starting capacitor 1 is connected in parallel with a driving capacitor 2 and both capacitors 1, 2 are connected in series with the feeder line 3 for a motor 4. A unit 5 for switching the starting capacitor 1 on/off is connected directly with the feeder line 3 for the motor 4 and connected in series with the starting capacitor 1. Three components are disposed in a single case 6 coupled with the motor 4. Electrical connection among three components and electrical connection between these components and the motor 4 are made through only two lines and the operation thereof is ensured with the same voltage as the motor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to starting and driving circuits for single-phase electric motors.

[Prior Art] Single-phase motors used, for example, to drive household appliances, office equipment, small power tools, etc. utilize the effect of a rotating magnetic field. However, starting these motors under load requires additional equipment and auxiliary equipment.

All devices capable of self-starting a single-phase motor are basically powered by an auxiliary starting winding Ap, which has the property of producing a magnetic flux that is significantly phase-shifted with respect to the main flux when the motor is at rest. It operates by creating a rotating magnetic field.

The auxiliary starting winding Ap is set perpendicular to the main winding Aa and is disconnected after the motor has started.

The phase difference between the current in the auxiliary circuit and the current in the main circuit can be obtained by connecting a capacitor in the auxiliary circuit so that the phase of the current advances with respect to one voltage, as is generally done. I can do it. In addition to single-phase induction motors of the type described above, this class of motors includes all induction motors with two windings, one of the two windings here called the auxiliary winding. has a capacitor connected thereto, so that the main and auxiliary windings remain permanently connected not only during start-up but also during normal continuous operation. Nevertheless, these motors usually do not have a high starting torque.

This is because the capacitance that must be connected to the auxiliary winding to obtain high starting torque becomes high when the motor increases speed.

In order to combine the good starting characteristics of single-phase capacitive motors with good operating characteristics without changing their dimensions and separation class, for example, it is common practice to connect two capacitors to an auxiliary circuit. , one of which is disconnected when the motor starts.

[Problem to be Solved by the Invention] This type of motor therefore currently requires the adaptation of three different parts: a starting capacitor, a driving capacitor and an automatic starting switch. An automatic activation switch can be obtained in several different ways. In one method, it is keyed to a centrifugal force switch or drive shaft.

This switch opens as soon as the motor reaches the set speed, shutting off the starting capacitor.

Another method is to connect a time delay relay to the circuit and open the contacts of the starting circuit after a delay of several seconds.

The third method is not automatic, but is added to the auxiliary contact or the main switch. The user holds this contact closed for several seconds during the activation period. This method runs the risk of damaging the motor if it fails to open the contacts correctly.

The first two methods described above are only moderately efficient, require the adaptation of three different components, require additional wiring, complicate the system, and are time consuming to maintain.

The aim of the invention is to eliminate the drawbacks as mentioned above.

[Means for Solving the Invention] The present invention comprises two capacitors with different capacitances connected in parallel to each other, the first capacitor being for starting and the second capacitor being for driving the motor, The two capacitors are connected in series with the power supply of the motor, and are further provided with a device for switching on/off the starting capacitor, and the device for switching the starting capacitor on/off is directly connected to the power supply line of the capacitor and connected to the driving capacitor. This problem is solved by a starting and driving circuit for a single-phase motor that operates at the same voltage as the motor. Furthermore, the device for switching the starting capacitor on and off and both capacitors are installed in the same container which can be connected to the motor.

One of the advantages of this invention is that automatic starting and driving of a single-phase motor can be performed at low cost by installing only one component (cylindrical shape) whose two terminals are connected to the power supply line.

[Example] The present invention will be described with reference to the accompanying drawings. A starting and driving circuit for a single-phase motor according to an embodiment of the invention comprises a starting capacitor 1 connected in parallel with a driving capacitor 2 . The capacitors are connected in parallel with each other, and both are connected in series with the power supply line 3 of the motor 4.

A device 5 for switching the starting capacitor 1 on and off is connected directly to the power supply line 3 of the motor 4 and is itself connected in series with the starting capacitor. Device 5 is therefore operated at the same voltage as starting capacitor 1 and driving capacitor 2.

All three parts are placed in a single container 6, which is connected to the motor 4, as shown in FIG.

In this way an electrical connection between three components, namely two capacitors (starting capacitor and driving capacitor)
The electrical connection between 1 and 2 and the device 5 and these parts and the motor 4 is made by only two wires, and its operation is ensured by the same voltage as the motor 4.

As shown in FIG.
is connected to a power supply line 3, and its output is connected to a delay circuit or filter 8. The delay circuit 8 delays the opening of a converter 9, usually a relay, which by calculating its capacitance can disconnect the starting capacitor at the desired moment when the motor starts.

In order to be able to operate the device correctly, the opening of the relay contacts of the converter 9 is further delayed by connecting another suitable capacitor 12 in parallel with the relay, which capacitance is charged and the normal voltage of the motor 4 is It is maintained at that potential during operation.

If the motor stops due to overload or other external causes, capacitor 12 will discharge through the pick-up coil of relay 9, thus delaying its opening. In this way, the motor always comes to a complete stop and the drive capacitor 2 discharges directly into the windings of the motor 4, without affecting the contacts of the relay 9, which could hitherto cause damage.

As a further protection of the converter 9, a discharge resistor 11 is connected in parallel with the starting capacitor 1. Device 5 is starting capacitor 1
When opening the circuit, the latter initially remains charged and then immediately discharges through the resistor 11. In this way, resistor 11 prevents a direct discharge into either capacitor 1 or the relay contacts of converter 9.

The device described above ensures a long service life of the on/off switching device 5. This is because they prevent power from being transmitted to the converter 9.

Although the present invention has been described above in connection with specific embodiments thereof,
Many modifications may be made without departing from the scope of the invention. Furthermore, it is clear that all details can be replaced by technically equivalent parts.

[Brief explanation of the drawing]

1 and 2 are schematic circuit diagrams of one embodiment of the present invention. FIG. 3 is a schematic diagram showing a practical application of the circuit shown in FIGS. 1 and 2. FIG. ■, 2... Capacitor, 4 diodes, 5... Switching device.

Claims (5)

[Claims] (1) It has two capacitors with different capacitances, the first capacitor is for starting and the second capacitor is for motor drive, and these two capacitors are connected in parallel with each other, and both of them are used for motor drive. In a starting and driving circuit for a single-phase motor, the starting and driving circuit is connected in series with a power source of the starting capacitor and further includes a device for switching on and off the starting capacitor, wherein the device for switching the starting capacitor on and off is connected to the power source of the starting capacitor and the driving capacitor. The device is directly connected and operated at the same voltage as the drive capacitor, and the device for switching the start capacitor on and off, the start capacitor and the drive capacitor are installed in a single container installed near the motor. Starting and driving circuit for single-phase motors. 2. The circuit according to claim 1, wherein the device for switching on and off the starting capacitor is connected in series with only the starting capacitor. (3) The device for switching the starting capacitor on and off is equipped with a rectifier, the input of which is connected to the power source of the motor,
2. The circuit of claim 1, the output of which is connected to a delay circuit or filter, the output of which is connected to a converter connected along the power supply of the starting capacitor. (4) The circuit according to claim 1, wherein a resistor is connected in parallel with the starting capacitor. (5) The circuit according to claim 4, wherein a capacitor is connected in parallel with the converter.