JP2007189847A - Brush mechanism for winding type induction motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brush mechanism for a winding type induction motor in which the current density flowing in a brush is optimized to optimally heat the brush even when a light load is applied, to form an oxidized film on a surface in slide-contact with the slip ring in the brush to prevent abnormal wear. <P>SOLUTION: When a rated load is applied, a brush B1 held by a brush holder BH1 and a brush B2 held by a brush holder BH2 are brought in slide-contact with a slip ring SR. When a light load is applied, the brush holder BH1 slides centering around a drive shaft S1 to separate the brush B1 from the slip ring SR, allowing current to flow only through the brush B2. Thus, the current density flowing in the brush B2 is made approximately equal to the value at the time of rating, and the oxidized film is properly formed on the brush B2 to enable stable operation even when underload is applied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a brush mechanism of a winding induction motor, and is devised so that an oxide film is appropriately generated on the surface of a brush even when a load fluctuates.

  In a winding induction motor, a rotor winding having the same number of poles as a stator winding is provided on the rotor core. The rotating shaft is provided with three slip rings individually connected to the windings of each phase of the rotor winding. Brushes are slidably contacted with the three slip rings, and resistors for starting and speed adjustment are connected via the brushes.

  In the operation of such a winding induction motor, the brush is an important element for feeding the secondary winding (rotor winding). Depending on the current density of the current flowing through the brush in operation, the brush material to be used, It is necessary to select an appropriate number of brushes.

More specifically, by setting the current density of the current flowing through the brush optimally, the brush is heated to an appropriate brush temperature by the contact resistance between the brush and the slip ring and the ohmic loss of the brush. An oxide film is formed on the surface of the film.
In this way, by forming an oxide film on the brush surface (the surface that is in sliding contact with the slip ring) with an appropriate brush temperature, it is possible to prevent abnormal wear of the brush and slip ring and to ensure good operation. .

  The material and the number of brushes are selected according to the current density of the current flowing through the brush. Generally, it is determined based on the rated current of the motor or the load current with the highest frequency of operation. That is, the brush material and the number of brushes are selected so that an oxide film is appropriately generated on the brush surface by heat generation due to the rated current (or load current with high operation frequency).

In practice, however, there are cases where the operation is lighter than the planned load. In this case, the current density is reduced and no oxide film is formed on the surface of the brush, resulting in abnormalities in the brush or slip ring. Wear may occur. Such abnormal wear may cause secondary winding burnout.
That is, in such a light load operation, the current density flowing through the brush is reduced, and therefore the heat generation temperature of the brush is low, the oxide film is not properly generated, and the brush and the slip ring may be abnormally worn. It is.

  In addition, there are many loads with a square-decreasing torque characteristic such as a blower and a pump in the use of a wound-type electric motor, and when performing speed control, it may become a very light load operation by decelerating. During such a light load operation, the current density flowing through the brush is reduced, which may cause the same problem.

  In view of the above-described prior art, the present invention adjusts the current density flowing through the brush to an optimum current density that can appropriately generate an oxide film on the brush surface even when the load fluctuates. An object of the present invention is to provide a brush mechanism.

The configuration of the present invention for solving the above problems is as follows.
In a wound induction motor in which a plurality of brushes individually held by a plurality of brush holders are in sliding contact with one slip ring,
A swing structure that supports at least one of the plurality of brush holders and swings the brush holder so that the brush held by the brush holder is in contact with and separated from the slip ring;
A current sensor for detecting a current flowing from the secondary winding of the induction motor to an external resistor;
A brush holder that compares the detected current value detected by the current sensor with a predetermined reference current value, and swings the swinging mechanism when the detected current value is equal to or greater than the reference current value. When the detected current value is less than the reference current value, the brush held by the brush is held in contact with the slip ring, and the brush held by the swinging brush holder is moved away from the slip ring. A controller for controlling the swinging by the swinging structure,
It is characterized by having.

The configuration of the present invention is as follows.
In the winding induction motor in which the brush held by the brush holder comes into sliding contact with the slip ring,
A heater provided in the brush holder for heating the brush;
A current sensor for detecting a current flowing from the secondary winding of the induction motor to an external resistor;
A current supply means for comparing a detected current value detected by the current sensor with a predetermined reference current value, and for supplying a current having a value inversely proportional to a deviation between the detected current value and the reference current value to the heater;
It is characterized by having.

  According to the present invention, when the total current value flowing through the secondary winding becomes small due to light load operation, the number of brushes slidably contacting the slip ring is reduced. The current density is substantially the same as that at the time of load, and an oxide film is appropriately generated on the brush surface by the heat generated by the brush slidingly contacting the slip ring. This oxide film can ensure good operation.

  Further, according to the present invention, when the total current value flowing through the secondary winding becomes small due to light load operation, the brush is heated by the heater to ensure the temperature of the brush and appropriately apply the oxide film on the brush surface. It is possible to ensure good operation with this oxide film.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on examples.

  FIG. 1 is a configuration diagram illustrating a main part of a brush mechanism of a winding induction motor according to a first embodiment of the present invention, and FIG. 2 is a configuration diagram illustrating a control system of the first embodiment.

  As shown in FIG. 1, the slip ring SR rotates together with the rotor of the wound induction motor. In FIG. 1, only one slip ring SR is shown, but in actuality, it is arranged corresponding to each phase, and there are a total of three slip rings.

  The brush B1 held by the first brush holder BH1 and the brush B2 held by the second brush holder BH2 are in sliding contact with one slip ring SR.

The first brush holder BH1 is swingably supported by an electric motor casing (not shown). By swinging, the brush B1 comes into contact with or separates from the slip ring SR.
The second brush holder BH2 is arranged in a fixed state in the motor casing, and the brush B2 held by the brush holder BH2 is always in sliding contact with the slip ring SR.

Here, the swinging structure of the first brush holder BH1 will be described.
The drive shaft S1 is rotatably supported by the motor casing. A gear G1 is fixed to the drive shaft S1, and a brush holder BH1 is fixed. A gear G2 meshes with the gear G1, and the gear G2 is rotated by a motor m.

When the gear G2 rotates in the forward or reverse direction by driving the motor m, the gear G1 rotates in the forward or reverse direction, and the brush holder BH1 swings in the forward or reverse direction about the drive shaft S1. Move. When the brush holder BH1 swings in the forward direction, the brush B1 held by the brush holder BH1 comes into sliding contact with the slip ring SR, and when the brush holder BH1 swings in the reverse direction, the brush holder BH1 The brush B1 held in the position separates from the slip ring SR.
The rotation direction and the rotation amount of the gear G1 are detected by limit switches LS1 and LS2. The contact / separation state of the brush B1 with respect to the slip ring SR can be determined from the rotation direction and the rotation amount of the gear G1.

  The structure shown in FIG. 1 is the same in the other two phases.

As shown in FIG. 2, three-phase AC power is supplied from the power supply unit 11 to the winding induction motor IM to which the first embodiment is applied, and the secondary side of the winding induction motor IM is connected via a connection line 13. The resistor 12 is connected. A current flowing from the secondary winding (rotor winding) of the winding induction motor IM to the resistor 12 through the slip ring and the brush flows through the connection line 13.
The connection line 13 is provided with a current sensor 14 such as a hall CT that detects a current flowing through the connection line 13.

  The detected current value a detected by the current sensor 14 is sent to the controller 15. The controller 15 controls the motor m that rotates the gear G2 forward and backward according to the detected current value a.

  Here, control by the controller 15 will be described. A reference current value b is set in the controller 15. The value of the reference current value b is such that when the current of this value (value b) flows through the two brushes B1 and B2, the two brushes B1 and B2 generate heat, and an oxide film is formed on the surfaces of the brushes B1 and B2. The value is generated.

  The controller 15 compares the detected current value a with the reference current value b. When the detected current value a is equal to or greater than the reference current value b, the controller 15 rotates the motor m in the forward direction, thereby moving the brush holder BH1 in the forward direction. And the brush B1 is brought into sliding contact with the slip ring SR. The swing amount of the brush holder BH1 is determined based on detection signals from the limit switches LS1 and LS2.

Because of such control, when a ≧ b, the two brushes B1 and B2 are in sliding contact with the slip ring SR. At this time, the current density flowing through each of the brushes B1 and B2 is an optimum current density that causes the brushes B1 and B2 to generate heat and an oxide film is generated on the brush surface.
Therefore, when the rated load or the load with a high operation frequency is applied, an oxide film is generated on the surfaces of the brushes B1 and B2 that are in sliding contact with the slip ring SR, and an excellent operation can be performed without causing abnormal wear.

  On the other hand, the controller 15 compares the detected current value a with the reference current value b, and when the detected current value a becomes less than the reference current value b, the controller 15 reverses the motor m, thereby reversing the brush holder BH1. The brush B1 is moved away from the slip ring SR by swinging in the direction. The swing amount of the brush holder BH1 is determined based on detection signals from the limit switches LS1 and LS2.

Because of such control, when a <b, only one brush B2 is in sliding contact with the slip ring SR. As described above, since the current flows only to one brush B2, even if the total current value decreases, the current density flowing to brush B2 causes the brush B2 to generate heat and generate an oxide film on the brush surface. It can be a density.
Therefore, even during light loads, an oxide film is generated on the surface of one brush B2 that is in sliding contact with the slip ring SR, and good operation can be performed without causing abnormal wear.

In the first embodiment, only one of the brush holders BH1 and BH2 is swung. However, both can be swung.
When both brush holders BH1 and BH2 are swung, the brush held by both brush holders is brought into sliding contact with the slip ring at rated load, and the brush held by one brush holder is separated from the slip ring at light load. Control to make it.
Of course, there are three or more brush holders, of which at least one brush holder is installed so as to be able to swing, and control is performed so that the brush held by the swinging brush holder is separated from the slip ring at light loads. May be.

  FIG. 3 is a configuration diagram showing a main part of a brush mechanism of a wound induction motor according to a second embodiment of the present invention, FIGS. 4 and 5 are perspective views showing a brush portion, and FIG. 6 is a second embodiment. It is a block diagram which shows this control system.

  As shown in FIG. 3, in the brush mechanism according to the second embodiment, the brush holder BH3 is fixedly arranged as in the prior art, holds the brush B3, and this brush B3 is slip ring (not shown in FIG. 3). (Not shown).

  Further, as shown in FIGS. 3 and 4, the brush B3 held by the brush holder BH3 is provided with a seat heater 20 so as to wrap around the brush B3.

As shown in FIG. 4, not only is the seat heater 20 provided around the brush B3, but the seat heater 20 is embedded in the brush B3 as shown in FIGS. 5 (a), 5 (b), and 5 (c). 20 may be attached to the peripheral surface of the brush B3, or the sheet heater 20 may be attached to the upper surface of the brush B3.
In any case, the sheet heater 20 is provided in the brush holder BH3, and when energized, it generates heat and heats the brush B3.

As shown in FIG. 6, three-phase AC power is supplied from the power supply unit 21 to the winding induction motor IM to which the second embodiment is applied, and the secondary side of the winding induction motor IM is connected via a connection line 23. The resistor 22 is connected. A current flowing from the secondary winding (rotor winding) of the winding induction motor IM to the resistor 22 through the slip ring and the brush flows through the connection line 23.
The connection line 23 is provided with a current sensor 24 such as a hall CT that detects a current flowing through the connection line 23.

  The detected current value d detected by the current sensor 24 is sent to the comparator 25. In this comparator 25, a reference current value e is set. The value of the reference current value e is set such that the current of this value (value of e) flows through the brush B3 so that the brush B3 generates heat and an oxide film is generated on the surface of the brush B3.

  The comparator 25 compares the detected current value d with the reference current value e and outputs a deviation signal f. The value of the deviation signal f decreases as the deviation (de) increases, and increases as the deviation (de) decreases. That is, the deviation signal f is a value obtained by inverting the deviation (d−e) (an inversely proportional value).

The amplifier 26 applies a voltage to the seat heater 20 with a voltage value corresponding to (amplified) the magnitude of the deviation signal f.
For this reason, when the rated load or the load with high operation frequency is used, the deviation signal f is small because the detected current value d is large, and no voltage is supplied from the amplifier 26 to the seat heater 20 (or only a small voltage is supplied). However, since the current density flowing through the brush B3 is high, an oxide film is generated on the brush surface, and good operation can be performed without causing abnormal wear.

On the other hand, when the load is light, since the detected current value d is small, the deviation signal f is increased, a voltage having a large voltage value is applied from the amplifier 26 to the seat heater 20, and current flows through the seat heater 20 to generate heat. Due to the heat generated by the seat heater 20, the temperature of the brush B <b> 3 rises, and an oxide film is generated on the brush surface, so that a good operation can be performed without causing abnormal wear.
That is, even when the current density flowing through the brush B3 is small, the heating of the brush B3 can be adjusted by adjusting the current flowing through the sheet heater 20, and the brush temperature can be made appropriate for the generation of the oxide film.

  In Example 2, the current flowing through the connection line is detected and the current flowing through the seat heater 20 is adjusted. However, the temperature of the brush B3 is detected, and this temperature becomes an appropriate temperature for generating an oxide film. As described above, the current flowing through the seat heater 20 may be adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the principal part of the brush mechanism of the winding type induction motor based on Example 1 of this invention. The block diagram which shows the control system of Example 1 of this invention. The block diagram which shows the principal part of the brush mechanism of the winding type induction motor based on Example 2 of this invention. The perspective view which shows the brush part of Example 2 of this invention. The perspective view which shows the brush part of Example 2 of this invention. The block diagram which shows the control system of Example 2 of this invention.

Explanation of symbols

11, 21 Power supply unit 12, 22 Resistor 13, 23 Connection line 14, 24 Current sensor 15 Controller 20 Seat heater 25 Comparator 26 Amplifier BH1, BH2, BH3 Brush holder B1, B2, B3 Brush SR Slip ring G1, G2 Gear m Motor LS1, LS2 Limit switch S1 Drive shaft

Claims (2)

In a wound induction motor in which a plurality of brushes individually held by a plurality of brush holders are in sliding contact with one slip ring,
A swing structure that supports at least one of the plurality of brush holders and swings the brush holder so that the brush held by the brush holder is in contact with and separated from the slip ring;
A current sensor for detecting a current flowing from the secondary winding of the induction motor to an external resistor;
A brush holder that compares the detected current value detected by the current sensor with a predetermined reference current value, and swings the swinging mechanism when the detected current value is equal to or greater than the reference current value. When the detected current value is less than the reference current value, the brush held by the brush is held in contact with the slip ring, and the brush held by the swinging brush holder is moved away from the slip ring. A controller for controlling the swinging by the swinging structure,
A brush mechanism for a wound-type induction motor. In the winding induction motor in which the brush held by the brush holder comes into sliding contact with the slip ring,
A heater provided in the brush holder for heating the brush;
A current sensor for detecting a current flowing from the secondary winding of the induction motor to an external resistor;
A current supply means for comparing a detected current value detected by the current sensor with a predetermined reference current value, and causing a current having a value inversely proportional to a deviation between the detected current value and the reference current value to flow to the heater;
A brush mechanism for a wound-type induction motor.

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