JPS6042706B2 - single phase induction motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to provide a small, lightweight, and inexpensive starting switch for a capacitor-started single-phase induction motor or a nine-phase-started induction motor.

Conventionally, the starting switch for single-phase induction motors has been a centrifugal force switch that uses centrifugal force, or a voltage relay or current relay that uses changes in voltage or current.
In the case of a centrifugal force switch, it is large and requires processing on the motor shaft to attach the rotating part of the centrifugal force switch, and the installation requires a lot of man-hours and has drawbacks such as being expensive.

Further, voltage and current relays have drawbacks such as being prone to malfunction due to changes in power supply voltage, being large in size, and being expensive. Note that Figure 1 shows a wiring diagram when a centrifugal force switch is used as the starting switch, and a centrifugal force switch 3 is connected in series to an auxiliary winding 2 that is connected in parallel to the main winding 1. .

Furthermore, as a starting switch for a special motor that improves the above-mentioned drawbacks, a starting switch using a positive temperature coefficient thermistor 4 as shown in FIG. 2 has been proposed, but in this case it has the following drawbacks. Ta.

(1) Since the positive temperature coefficient thermistor 4 is connected in series with the auxiliary winding 2, at the time of starting, all the starting current flowing through the auxiliary winding 2 flows through the positive temperature coefficient thermistor 4, so the allowable current will be reduced for high output devices. It needs to be bigger.

(2) At the time of starting, the starting current flowing through the PTC thermistor 4 causes a voltage drop, the voltage of the auxiliary winding 2 decreases, and the starting torque decreases.

(3) If the power is applied and the power is turned off after normal operation, and then the power is immediately reapplied, the positive temperature coefficient thermistor 4 has not cooled down enough and has a high resistance, causing the circuit of the auxiliary winding 2 to It becomes almost non-conductive, and since the circuit consists of only the main winding 1, it will not start and will be in a locked state.

The present invention has been made in view of the above-mentioned conventional drawbacks, and one embodiment of the present invention will be described below with reference to FIGS. 3 to 5.

In Fig. 3, 1 is a main winding, 2 is an auxiliary winding connected in parallel to the main winding 1, 5 is a start switch connected in series to the auxiliary winding 2, and a bimetal contact 6 is connected in series to this bimetal contact 6. An excitation coil 8 is connected in parallel to the connected relay contact 7 and the series circuit of the bimetal contact 6 and the relay contact 7.
It consists of: Note that the bimetal contact 6 is normally closed, and when a certain current flows through the bimetal contact 6, it is activated and opened after a certain period of time, and it is configured to automatically return after a certain period of time. ing. Furthermore, the excitation coil 8 has an extremely large impedance with respect to the impedance of the auxiliary winding 2 and the power supply voltage. Furthermore, the relay contact 7 is normally closed, and the exciting coil 8
The structure is such that it operates and opens when a voltage is applied to it. Next, the operation will be explained with reference to FIGS. 4 and 5.

When the power is turned on, since the relay contact 7 and the bimetal contact 6 are closed, current flows through the main winding 1 and the auxiliary winding 2, the torque becomes T1 in Fig. 5, and the rotation is at the intersection with the load curve L. It is operated by several A. When the time is set in advance,
The bimetal contact 6 is actuated by the current flowing through the auxiliary winding 2, and the bimetal contact 6 is opened. When the bimetal contact 6 opens, a voltage is applied to the excitation coil 8, and the relay contact 7 immediately opens. At this time, a current flows to the auxiliary winding 2 through the excitation coil 8, but since the impedance of the excitation coil 8 is set to be large, the current flowing to the auxiliary winding 2 is extremely small. Therefore, since virtually no current flows through the circuit of the auxiliary winding 2, the motor torque becomes T2 in FIG. 5, and the motor is operated at the rated rotation speed B. During this time, since the relay contact 7 remains open, current no longer flows through the bimetal contact 6, and returns after a certain period of time, and the bimetal contact 6 closes. Therefore, when the power is turned off and then turned on again, both the bimetal contact 6 and the relay contact 7 are closed, which is the same as the initial state, and the above operation is repeated until the rated rotation speed B is reached. be driven. As is clear from the above description, the present invention provides excellent effects such as being able to perform reliable starting with a simple configuration, and also being able to provide a small, lightweight, and inexpensive starting switch.

[Brief explanation of the drawing]

Figures 1 and 2 are wiring diagrams of a conventional electric motor equipped with a starting switch, Figure 3 is a wiring diagram of a single-phase induction motor according to an embodiment of the present invention, and Figure 4 is the operation of each part of the motor. An operation explanatory diagram showing the state, and FIG. 5 is a characteristic diagram showing the relationship between the rotation speed and torque of the same motor. 1... Main winding, 2... Auxiliary winding, 5... Starting switch, 6... Bimetal contact, 7... Relay contact,
8... Excitation coil.

Claims (1)

[Claims] 1 In a capacitor-start type or split-phase start type single-phase induction motor in which a starting switch is connected in series to an auxiliary winding connected in parallel to the main winding, the starting switch is a bimetallic motor operated by a current flowing through the auxiliary winding. A single-phase induction motor consisting of a series circuit in which normally closed relay contacts are connected in series to the contacts, and an excitation coil connected in parallel to the series circuit.