JPH07303355A - Method for adjusting speed of induction motor - Google Patents

Abstract

PURPOSE:To provide a method for adjusting speed of an induction motor for low output and high rated voltage without changing the size of the stator of the motor by suppressing the temperature rise of the motor by eliminating the need of a winding for adjusting speed from the motor. CONSTITUTION:A power source 8 is connected to a main winding 1 and speed change-over switch 7 and the winding 1 is connected in series with an auxiliary winding 2. The auxiliary winding 2 is connected in parallel with two capacitors A3 and B4 which are connected in series with each other. The speed change-over switch 7 which is used for switching the operating speed of an induction motor is connected to a leader line for high-speed operation led out from the connection between the capacitors A3 and B4 and another leader line 6 for low-speed operation led out from the connection between the auxiliary winding 2 and capacitor A3 so that the switch 7 can switch one of the lines 5 and 6 to the other at the time of adjusting the speed of the induction motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed adjusting method for an induction motor.

[0002]

2. Description of the Related Art Conventionally, an induction motor speed adjusting method is shown in FIG.
The main winding 101 and the auxiliary winding 102 are connected in parallel, and the auxiliary winding 102 and the capacitor 103 are connected in series. When the speed adjustment operation is performed, a tap is pulled out from the middle of the auxiliary winding 102, the auxiliary winding 102 and the speed adjustment winding 104 are divided, and the main winding 101 and the speed adjustment winding 104 are connected to each other. A method is used, which includes a strong operation lead wire 105 and a speed change switch 107 for switching the connection between the auxiliary winding 102 and the weak operation lead wire 106 formed by tapping the speed adjustment winding 104. Especially for the induction motor used for overseas products with low output and high rated voltage, the main winding 1
01, the wire diameter of the auxiliary winding 102 becomes thin, which is likely to cause a disconnection accident. Therefore, as a countermeasure against this, the main winding 101 and the auxiliary winding 102 are connected in series as shown in FIG. The capacitor 103 is connected in parallel.
When performing the speed adjustment operation, a tap is pulled out from the middle of the main winding 101, and the main winding 101 and the speed adjustment winding 104
Divided into the main winding 101 and the speed adjustment winding 104, and the lead wire 105 for strong operation that is formed by tapping the speed adjustment winding 104, and the speed adjustment winding 1
The method constituted by the speed changeover switch 107 for changing over the connection with the lead line for weak operation 106 from the winding end portion of 04 was used.

[0003]

When adjusting the speed of an induction motor having such a small output and a high rated voltage, the speed adjustment divided from the main winding 101 is necessary in order to widen the range of the speed adjustment. It is necessary to increase the number of turns of the winding 104. However, if the number of windings of the speed adjusting winding 104 that is not used during the heavy duty operation is increased, the number of turns of the main winding 101 is correspondingly reduced, so that the current flowing through the main winding increases and the temperature of the induction motor rises during the heavy duty operation. Becomes higher. That is, as compared with the case where the rated voltage is low at the same output, the speed adjustment winding 104 that is not used during strong operation is required, so the amount of copper in the conductor is increased or the volume of the stator is increased as a measure against temperature rise. However, there is a problem that the cost becomes high.

Further, in the case of designing the winding, if the characteristic at the time of heavy operation is designed as a reference first, the number of windings of the speed adjusting winding becomes too large to fit in the target of weak operation, so that it cannot be accommodated in the slot. There is also a problem that it takes time to redesign the winding.

The present invention solves the above-mentioned problems, and at all speeds of an induction motor, since there is no unused conductor in the windings inserted in the slots of the stator, the same output and rated voltage are used. Since the temperature rise is equal to or higher than that in the case where the temperature is low, the first object is to propose a method of adjusting the speed of the induction motor without increasing the amount of copper in the conductor and without changing the volume of the stator.

A second object is to provide a method for reducing the design time for adjusting the speed of an induction motor.

[0007]

SUMMARY OF THE INVENTION In order to achieve the first object of the method of adjusting the speed of an induction motor of the present invention, the first means is separately inserted into a plurality of slots of the stator of the induction motor. A main winding, an auxiliary winding connected in series to the main winding, and a plurality of series-connected capacitors connected in parallel to the auxiliary winding. The connection between the outgoing line and the outgoing line extending from the connection part of each capacitor is switched.

In order to achieve the second object, the second
This means is provided with a switch for switching a plurality of capacitors connected in parallel to the auxiliary winding between series connection and parallel connection.

[0009]

According to the present invention, since the output of the first means is small and the conductor which is not used at all speeds of the induction motor used for the overseas products having a high rated voltage is not required, the temperature rise can be reduced. Also, the amount of copper used for the conductor can be reduced, and there is no need to change the volume of the stator.

In addition, since the configuration of the second means makes it possible to calculate and adjust the combined capacitance when the capacitors are connected in series and in parallel, the speed adjustment can be easily designed.

[0011]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. As shown in the figure, when operating strongly or weakly, the power supply 8 is connected to the main winding 1 and the speed changeover switch 7, and the main winding 1 and the auxiliary winding 2 are connected in series. Is connected in parallel with two capacitors A3 and B4 connected in series. The speed changeover switch 7 is the capacitor A3.
Is connected so as to be switched to a strong operation lead wire 5 extending from a connection portion of the capacitor B4 and the auxiliary winding 2 and a weak operation lead wire 6 extending from a connection portion of the capacitor A3.

In the above-mentioned structure, when the speed changeover switch 7 is connected to the strong operation lead wire 5, the result is as shown in FIG. 2, and the induction motor is in strong operation. The characteristic of the induction motor in this strong operation is the capacitor B4.
When the capacitance is constant, increasing the capacitance of the capacitor A3 as shown in FIG. 4 increases the torque, and decreasing the capacitance tends to decrease the torque. Further, as shown in FIG. 5, when the electrostatic capacity of the capacitor A3 is constant and the electrostatic capacity of the capacitor B4 is increased at the same torque, the input value of the induction motor decreases, and when the electrostatic capacity of the induction motor exceeds a certain fixed value, the input value is input. It has the characteristic that the value does not decrease. Further, when the speed changeover switch 7 is connected to the weak operation lead wire 6, the result is as shown in FIG. 3, and the induction motor is in a weak operation. The characteristic of the induction motor in this weak operation is determined by the combined capacitance of the capacitors A3 and B4 connected in series, which is determined by the strong operation characteristic. It is possible to change the speed. If the electrostatic capacity of the capacitor A3 is left unchanged and the electrostatic capacity of the capacitor B4 is increased, the speed can be increased, and if the electrostatic capacity is decreased, the speed can be decreased.

As described above, when the speed adjusting method for an induction motor of the present invention is used, conductors that are not used at all speeds are eliminated, the temperature rise of the induction motor can be reduced, and the amount of copper in the conductor is small. I'm sorry.

In the present embodiment, the speed of the capacitor is adjusted in two stages with two kinds of capacitances. However, the number of capacitors connected in series is increased, and a lead wire is taken out from the connection portion of each capacitor to switch. If so, the speed adjustment can be adjusted in multiple stages.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG. The same parts as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted. As shown in the figure, the capacitor C9 is connected to the contact G13 and the switch E11, and the capacitor D10 is connected to the contact I.
15 and a switch F12, the switch E11 is switched to a contact I15 and a contact H14, and the switch F12 is connected to be switched to a contact G13 and a contact H14.

In the configuration as described above, the switch E1
When 1 is connected to the contact I15 and the switch F12 is connected to the contact G13, the induction motor has a combined electrostatic capacitance when the capacitors C9 and D10 are connected in parallel, and the induction motor is operated strongly. Further, the switch E11 is connected to the contact H14, and the switch F is
When 12 is connected to the contact H14, the induction motor has a combined electrostatic capacitance when the capacitors C9 and D10 are connected in series, and the operation is weak.

As described above, when the speed adjusting method of the induction motor of the present invention is used, the speed of the induction motor can be adjusted by the combined capacitance of the series connection and the parallel connection of the two types of capacitors, which facilitates the design. Become.

[0018]

As is apparent from the above description of the embodiments, according to the present invention, since there is no conductor which is not used at all speeds of an induction motor having a small output and a high rated voltage, it is possible to reduce the temperature rise. Therefore, the amount of copper used for the conductor can be reduced, and a low-cost speed adjusting method can be provided.

Further, by the constitution of the second means, it is possible to calculate and adjust the combined electrostatic capacitance when the capacitors are connected in series and in parallel, so that a method capable of shortening the design time for speed adjustment is provided. it can.

[Brief description of drawings]

FIG. 1 is a connection diagram of a speed adjusting method according to an embodiment of an induction motor of a first embodiment of the present invention.

FIG. 2 is a connection diagram at the time of heavy operation according to an embodiment of the induction motor.

FIG. 3 is a connection diagram during weak operation according to an embodiment of the same induction motor.

FIG. 4 is a rotational speed-torque characteristic diagram during strong operation according to an embodiment of the same induction motor.

FIG. 5 is a capacitance-input characteristic diagram during weak operation according to an embodiment of the induction motor.

FIG. 6 is a connection diagram of a speed adjusting method according to an embodiment of the induction motor of the second embodiment.

FIG. 7 is a wiring diagram of a conventional speed adjustment method for an induction motor.

FIG. 8 is a wiring diagram of a method for adjusting the speed of the induction motor of the same low output and high rated voltage.

[Explanation of symbols]

 1 Main winding 2 Auxiliary winding 3 Capacitor A 4 Capacitor B

Claims (2)

[Claims] 1. A main winding inserted into a plurality of slots of a stator of an induction motor, an auxiliary winding connected in series with the main winding, and connected in parallel to the auxiliary winding. Speed of an induction motor, which is composed of a plurality of capacitors connected in series, and whose speed is adjusted by switching the connection between the lead wire extending from the connecting portion of the auxiliary winding and the capacitor and the lead wire extending from the connecting portion of each capacitor. Adjustment method. 2. The speed adjusting method for an induction motor according to claim 1, further comprising a switch for switching a plurality of capacitors connected in parallel to the auxiliary winding between a series connection and a parallel connection.