JP2003217413A - Motor protective device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor protective device capable of protecting a three- phase motor from overcurrent without causing high cost and upsizing of a motor stator. <P>SOLUTION: A bimetal part 18 of a bimetal type contact opening/closing mechanism part is forked into two branches from the midway. Each moving contact 12a and 15a is provided at the distal ends. Two fixed contacts 12b and 15b corresponding to each of the moving contacts 12a and 15a are electrically insulated. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor protection device for protecting a three-phase motor such as a three-phase DC brushless motor from overcurrent. 2. Description of the Related Art Conventionally, as a method for protecting a three-phase motor from overcurrent, as shown in FIGS. 7 and 8, a heating value of a motor current flowing through a motor coil MC is determined by using a thermal protector TP or a thermistor. T, etc., and when the heat value detected by these temperature detecting elements reaches a set value, the relay R is operated to cut off the motor current, or as shown in FIG. There is a method of using a thermal protector TP to protect a three-phase motor from overcurrent. However, the method shown in FIG. 7 has a drawback that the cost is high because a relay R and a relay power supply are used in addition to the thermal protector TP. In addition, the method shown in FIG. 8 requires a relay drive circuit RDC in addition to the thermistor T and the relay R, and thus has the disadvantage that the cost is increased as in the method shown in FIG. On the other hand, the method shown in FIG. 9 does not require a relay or a relay drive circuit, so that the cost does not increase. However, the three-phase motor is protected from overcurrent by using two thermal protectors such as a bimetal switch. Because of the protection method, the mounting space for the thermal protector is increased, and the motor stator may be increased in size. Also,
In the case of the method shown in FIG. 8, the operating temperatures of the two thermal protectors may be different depending on the installation position or the like. For this reason, since the current continues to flow between the remaining two phases, normal torque is not generated until the thermal protector reaches the operating temperature, hunting occurs, and abnormal vibration occurs. Accordingly, the present invention has been made in view of such problems, and a motor protection device capable of protecting a three-phase motor from overcurrent without increasing costs or increasing the size of the motor stator. The purpose is to provide. [0005] In order to achieve the above object, the present invention provides a motor protection device including a sealed case and a bimetallic contact opening / closing mechanism provided in the sealed case. A bimetallic part of the bimetallic contact opening / closing mechanism is bifurcated from the middle, and one movable contact is provided at a tip thereof, and two fixed contacts respectively corresponding to these movable contacts are electrically insulated. It is characterized by having been done. With such a configuration, a relay becomes unnecessary and the number of thermal protectors is reduced by half.
The three-phase motor can be protected from overcurrent without increasing the cost or increasing the size of the motor stator. Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are views for explaining one embodiment of the present invention, FIG. 1 is a plan view of a motor protection device according to one embodiment of the present invention, FIG. 2 is a side view of the same motor protection device, FIG. 3 is a sectional view taken along the line III-III in FIG. 1, FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1, and FIG. 5 is a perspective view showing a main part of the motor protection device shown in FIG. As shown in FIGS. 1 to 5, a motor protection device 10 according to an embodiment of the present invention
The closed case 11 is provided with a bimetallic contact opening / closing mechanism section 12 that opens and closes in accordance with the amount of heat generated by the motor current flowing through the motor coil of the three-phase motor. The sealed case 11 has a switch housing recess 1 in the center.
11a, a first connection terminal plate 112 provided on the closed case main body 111, and a right half on the first connection terminal plate 112 via an insulating sheet 113. Second connection terminal plate 1 provided
And a third connection terminal plate 11 provided on the left half of the first connection terminal plate 112 via an insulating sheet 115.
The first connection terminal plate 112 and the insulating sheets 113 and 115 have opening windows formed in the central portions thereof. The bimetallic contact switching mechanism 12 has a movable contact member 12a and a fixed contact member 12b. The movable contact member 12a is electrically connected to a first connection terminal 13 formed on a first connection terminal plate 112. It is connected to the. On the other hand, the fixed contact member 12b is electrically connected to the second connection terminal 14 formed on the second connection terminal plate 114, and the two connection terminals 13 and 14 are electrically insulated by the insulating sheet 113. . A second bimetallic contact opening / closing mechanism 15 is provided in the sealed case 11. This second
The bimetallic contact opening / closing mechanism section 15 is a movable contact member 15
a and the fixed contact member 15b.
5a is electrically connected to the first connection terminal 13 formed on the first connection terminal plate 112. Therefore, the first connection terminal 13 is a common connection terminal for the movable contact members 12a and 15a. The bimetallic portion 18 of the bimetallic contact opening / closing mechanism portions 12 and 15 is integral with each other, and is branched into two portions on the base side slightly from the portion where the movable contact is provided. That is, the movable contacts 12a and 15a are one bimetal 1
8 attached. On the other hand, the fixed contact member 15b is electrically connected to the third connection terminal 16 formed on the third connection terminal plate 116, and the third connection terminal 16 is connected to the first connection terminal 13 by the insulating sheets 113 and 114. And the second
It is electrically insulated from the connection terminal 14. The bimetal 18 is provided with the rivet 17 so that
11a is attached to the bottom surface. The motor protection device 10 constructed as described above
Is used as a thermal protector for a three-phase motor, as shown in FIG. 5, the first connection terminal 13 of the motor protection device 10 is connected to the star connection CP of the three-phase motor, and Connect the connection terminal 14 to the three-phase motor U
The phase motor coil MC _U, connect respectively the third connecting terminal 16 to the W-phase motor MC _W of the three-phase motor. Here, the three-phase motor U-phase motor coil MC _U or W-phase motor M
When a motor current exceeding the allowable current flows through C _W , the bimetallic contact opening and closing mechanisms 12 and 15 open simultaneously to cut off the current supplied to the motor coil. Therefore,
In this embodiment, the three-phase motor can be protected from overcurrent without using a relay, so that cost can be reduced. Further, since the number of thermal protectors used is reduced by half and the mounting space is reduced, it is possible to prevent the motor stator from becoming large. As described above, in the motor protection device according to the present invention, the bimetal portion of the bimetallic contact opening / closing mechanism is branched into two forks from the middle, and one movable contact is provided at the tip thereof. , Corresponding to each of these movable contacts
Since the three fixed contacts are electrically insulated, relays become unnecessary and the number of thermal protectors used is reduced by half, so that a three-phase motor can be used without increasing costs or increasing the size of the motor stator. This has the effect that the current can be protected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a motor protection device according to an embodiment of the present invention. FIG. 2 is a side view of the motor protection device shown in FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 2; FIG. 4 is a sectional view taken along line IV-IV in FIG. 2; FIG. 5 is a perspective view showing a main part of the motor protection device shown in FIG. 1; FIG. 6 is a diagram showing a circuit configuration when the motor protection device of FIG. 1 is used as a thermal protector for a three-phase motor. FIG. 7 is a diagram showing a first conventional example. FIG. 8 is a diagram showing a second conventional example. FIG. 9 is a diagram showing a third conventional example. [Description of Reference Numerals] 11 Sealed case 12 First bimetallic contact switching mechanism 12a Movable contact member 12b Fixed contact member 13 First connection terminal 14 Second connection terminal 15 Second bimetallic contact switching mechanism 15a Movable contact member 15b Fixed contact member 16 Third connection terminal

Claims (1)

Claims 1. A motor protection device comprising: a sealed case; and a bimetallic contact opening / closing mechanism provided in the sealed case, wherein the bimetallic contact opening / closing mechanism comprises a bimetallic contact opening / closing mechanism. A motor protection device characterized in that a portion is bifurcated from the middle, one movable contact is provided at the tip, and two fixed contacts respectively corresponding to these movable contacts are electrically insulated.