JPH0578194U - Capacitor discharge circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a capacitor discharge device panel that can be discharged safely. [Structure] A discharge resistor is formed by connecting a plurality of resistors in series, and a drive coil of an electromagnetic contactor is connected in parallel with the remaining resistor except a predetermined one of the plurality of resistors. And connecting the contacts of the electromagnetic contactor in parallel with the adjacently connected resistor.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a capacitor discharge circuit for safely discharging a large-capacity capacitor used in a voltage source inverter or the like.

[0002]

[Prior Art]

 FIG. 3 shows a conventional capacitor discharge circuit disclosed in, for example, Japanese Utility Model Laid-Open No. 58-90091. In the figure, 1 is a power supply device, 2 is a capacitor connected to the power supply device 1, 3 is a resistor having one end connected to one end of the capacitor 2, 4 is the other end of the resistor 3 and the other end of the capacitor 2. A semiconductor switch 5 connected to the semiconductor switch 5 is a control device for giving a signal to the semiconductor switch 4.

Next, the operation will be described with reference to the operation diagram of FIG. During normal operation, since the resistor 3 is separated by the semiconductor switch 4, no discharge current flows. As shown in FIG. 4, the capacitor voltage is charged by the supply voltage of the power supply device 1. When the device such as an inverter needs to be discharged due to the stoppage of the device, the semiconductor switch 4 is turned on by a signal given from the controller 5 and a current is passed through the resistor 3, so that the capacitor 2 is expressed by the formula (1). Discharge with exponential voltage value.

[0004]

[Equation 1]

As described above, the semiconductor switch 4 is used to prevent unnecessary current from flowing through the resistor 3 during operation.

[0006]

[Problems to be solved by the device]

 Since the conventional capacitor discharge circuit is configured as described above, expensive semiconductor switches must be used under high voltage, and the control circuit and high voltage circuit that give control signals to the semiconductor switches must be used. There was a problem that the insulation from the product was expensive.

The present invention has been made to solve the above problems, and an object thereof is to obtain a low-cost capacitor discharge circuit even in a high voltage circuit.

[0008]

[Means for Solving the Problems]

 The discharging circuit of the capacitor according to the present invention is formed by connecting a discharging resistor in series with a plurality of resistors and connecting in parallel with the remaining resistors except a predetermined one of the plurality of resistors. The drive coil of the electromagnetic contactor is connected, and the contact of the electromagnetic contactor is connected in parallel with the adjacently connected resistor.

[0009]

[Action]

 The discharging resistor of the capacitor discharging circuit according to the present invention operates so that the series resistance value is large when the circuit voltage is high and the series resistance value is small when the circuit voltage is low.

[0010]

【Example】

 Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. 1 is a circuit diagram of a capacitor discharge circuit according to a first embodiment of the present invention. In the figure, 1 is a power supply circuit, 2 is a capacitor connected to the power supply circuit 1, 11 to 14 are resistors connected in series, and the resistor 11 at one end is one end of the capacitor 2 and the resistor 14 at the other end. The other end is connected to the other end of the capacitor 2, and a discharging resistor 15 is constituted by 11 to 14. Drive coils 21 to 23 of the electromagnetic contactor connected in series are connected in parallel with the resistors 11 to 13 excluding the resistor 14 at the other end. Reference numerals 21a to 23a denote contacts of the electromagnetic contactor, which are connected in parallel with the remaining resistors 12 to 14 excluding the resistor 11 at one end.

Next, the operation will be described with reference to FIG. FIG. 2a shows the voltage on the capacitor 2. When the device voltage, that is, the voltage of the capacitor 2 is low, all but the resistor 11 of the discharge resistor 15 are short-circuited by the contacts of the electromagnetic contactor. With the bias of 23, the contacts 21a to 23a are opened to open the short circuit, and at the rated voltage, all the resistors 11 to 14 are connected in series. 2b shows the drive coil voltage of the electromagnetic contactor 21, FIG. 2c shows the drive coil voltage of the electromagnetic contactor 22, and FIG. 2d shows the drive coil voltage of the electromagnetic contactor 23.

At the time when the device is stopped and a discharge is required, all the resistors 11 to 13 are connected to the discharge resistor 15, so that the capacitor voltage drops as a function of the equation (2), The voltage of the drive coil of each of the electromagnetic contactors 21-23 also decreases sequentially.

[0013]

[Equation 2]

When the voltage of the capacitor 2 reaches the drop voltage of the electromagnetic contactor (normally about 1/3 of the pickup voltage), the electromagnetic contactors 21 to 23 are naturally turned off and the resistors 12 to 14 are short-circuited in sequence. ..

Example 2. In Example 1, the dropout voltages of the electromagnetic contactors 21 to 23 were all the same. However, if the dropout voltages are not the same, the discharge resistance value becomes low with a slight delay, and thus the final value. Specifically, it switches to discharge with a short time constant according to equation (1).

Example 3. The discharge resistors 11 to 14 may have a resistance value according to need. However, in order to make the discharge time approximately the same as the conventional one, the respective resistance values are the same as those of the conventional discharge resistor 3. About 1/2 is suitable.

Example 4. In the first embodiment, three electromagnetic contactors and four resistors forming the discharging resistor are used. However, when a higher voltage is required, the electromagnetic contactor and the discharging resistor are formed. The number of resistors to be used may be increased.

Example 5. In order to perform the discharge more linearly in a short time, the desired characteristics may be obtained by configuring the electromagnetic contactor with different dropout voltages or by changing the resistance value of the discharging series resistor. ..

[0019]

[Effect of the device]

 As described above, according to the present invention, a discharging resistor is formed by connecting a plurality of resistors in series, and is parallel to the remaining resistors except a predetermined one of the plurality of resistors. Since the drive coil of the electromagnetic contactor is connected and the contact of the electromagnetic contactor is connected in parallel with the resistor connected adjacently, the voltage of the electromagnetic contactor is the one that is the same as the capacitor voltage. Therefore, there is an effect that a capacitor discharge circuit with a fast discharge time can be constructed at low cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a capacitor discharge circuit according to a first embodiment of the present invention.

FIG. 2 is an operation characteristic diagram of a capacitor discharge circuit according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional capacitor discharge circuit.

FIG. 4 is an operation characteristic diagram of a conventional capacitor discharge circuit.

[Explanation of symbols]

 1 Power supply 2 Capacitor 11-14 Resistor 15 Discharge resistor 21-23 Electromagnetic contactor drive coil 21a-23a Electromagnetic contactor contact

Claims (1)

[Scope of utility model registration request] 1. A magnetic contactor comprising a discharging resistor formed by connecting a plurality of resistors in series, and in parallel with the remaining one of the resistors except a predetermined one of the plurality of resistors. And a contact of the electromagnetic contactor is connected in parallel to the resistor different from the resistor connected to the drive coil.