JPS6114755B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a starting circuit for a single-phase induction motor using a starter by connecting a positive temperature coefficient thermistor in series with the starting coil, and in particular to controlling two-phase operation time to reduce power consumption during starting. The purpose is to minimize losses.

Conventionally, the starting circuit for a single-phase induction motor (hereinafter simply referred to as a motor) using a positive temperature coefficient thermistor as a starter consists of a starting switch A such as a thermostat, a motor B, and a starting coil of the motor B connected in series, as shown in Figure 1. Connected positive characteristic thermistor C and starting capacitor D (omitted for split-phase starting motors)
I was confused. In this configuration, when the motor circuit is closed by the start switch A, the positive characteristic thermistor (Fig. 4A)
point) due to self-heating due to energization, the resistance value increases to 10 ⁵
When the resistance reaches ~10 ⁶ Ω (point D in Figure 4), the starting coil becomes disconnected from the power supply circuit. In other words, current flows to the starting coil for only a few seconds when the positive temperature coefficient thermistor C becomes high in resistance due to self-heating (two-phase operation).
This contributes to starting the motor, and after that, current flows only to the main coil B', and high-efficiency operation begins. However, the heat-up time of the positive temperature coefficient thermistor that determines the two-phase operation time of this motor depends on the room temperature resistance value of the positive coefficient thermistor C, element size, Kiuri point, withstand voltage, durability, motor starting current, and motor restartability. In particular, in capacitor-started motors where the starting coil current at startup is small, the heat-up time of a positive temperature coefficient thermistor is longer (the amount of heat generated by a positive coefficient thermistor is proportional to the square of the current). ), it is considerably longer than the two-phase operation time required to start the motor, and the unnecessary two-phase operation time is longer than a mechanical relay that detects current changes in the main coil and opens the starting coil side circuit. However, it has the disadvantage of high power consumption.

The present invention focuses on this drawback and aims to optimize the two-phase operation time of the motor by controlling the heat-up time of the positive temperature coefficient thermistor, thereby minimizing the increase in power consumption during startup. .

An embodiment of the present invention will be described below with reference to the drawings. In the figure, 1 is a power source, 2 is a starting switch such as a thermostat, 3 is a motor (single-phase induction motor), 3a is a main coil, and 3b is a starting coil. 4 is a positive characteristic thermistor, 5 is the main coil 3
A starting capacitor 6 provides a phase difference between the starting coil 3b and the starting coil 3b to facilitate starting, and 6 is a delay timer connected in series to the main coil circuit. It is now energized (see the time chart in Figure 3).

In this starting circuit, by energizing only the circuit on the starting coil 3b side without energizing the main coil 3a through which most of the starting current flows for a certain period of time T _O (Fig. 3) after turning on the starting switch 1, The positive temperature coefficient thermistor 4 is preheated to bring the temperature of the positive coefficient thermistor close to the Curie point (point C in Figure 4), generally around 120°C (Figure 4 A→B).
Thereafter, by energizing the main coil 3a, the heat-up time of the PTC thermistor 4 can be shortened, and as a result, the heat-up time can be adjusted to the two-phase operation time required for the motor. It is possible to significantly reduce power consumption during startup, which was associated with the conventional method. Note that the delay time T _O by the delay timer 6 is a value determined from the characteristics of the positive characteristic thermistor (basic resistance value, element size, Curie point) and the characteristics of the motor (starting coil current, required two-phase operation time). .

As is clear from the above description, the present invention has a positive temperature coefficient thermistor connected in series to a starting coil, and the positive temperature coefficient thermistor is connected to the motor before voltage is applied to the motor by the operation of a controller such as a thermostat. Since it is equipped with a control device that flows a predetermined current for a predetermined time only in the starting coil side circuit of the exercise machine, by controlling the heat-up time of the positive temperature coefficient thermistor, the two-phase operation time of the motor is reduced. It can be optimized to suit the time and minimize the high input two-phase operation time. As a result, the activation method using a positive temperature coefficient thermistor is essentially superior to the conventional current detection type mechanical relay. The power loss during startup can be eliminated, and the benefits of the positive temperature coefficient thermistor startup system, such as no contact, light weight, and standardization, can be fully utilized, which has a great effect.

[Brief explanation of the drawing]

Fig. 1 is a starting circuit diagram of a single-phase induction motor using a conventional positive characteristic thermistor, Fig. 2 is a starting circuit diagram of a single-phase induction motor showing an embodiment of the present invention, and Fig. 3 is the circuit of Fig. 2. FIG. 4 is a resistance temperature curve (RT curve) of a positive temperature coefficient thermistor. 3...Motor, 3a...Main coil, 3b...Starting coil, 4...Positive characteristic thermistor, 6...Delay timer (control device).

Claims (1)

[Claims] 1. In a device that has a positive temperature coefficient thermistor connected in series with the starting coil, before applying voltage to the motor by operating a controller such as a thermostat,
A starting circuit for a single-phase induction motor, comprising a control device that causes a predetermined current to flow for a predetermined time only in a starting coil side circuit of the motor that includes the positive temperature coefficient thermistor.