JPH09298076A - Automatic polarity matching dc power source cord - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the work and enhance the safety by providing an automatic polarity matching circuit and an ac output preventing circuit between an input terminal and an output terminal. SOLUTION: An input terminal 11 has an inductance 12, an electromagnetic switch 13, and a rectifying element 14, and the contacts 13A, 13B of the electromagnetic switch 13 are interposed along a power source line. When a dc voltage is connected to the input terminal, an output terminal 8 can obtain a constant polarity by the rectifying element 14 regardless of the polarity connected to the input terminal. Since the voltage drop by the inductance is small when the dc voltage is connected to the input terminal, the electromagnetic switch 13 is operated to close 13A, 13B, whereby a dc output is supplied to the output terminal. Since the electromagnetic switch 31 can not be operated when an ac power source is connected to the input terminal, no ac output is supplied to the output terminal. According to such a structure, simplification of work, prevention of damage of equipment, and improvement in safety can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic polarity matching type DC power cord used when laying a power cord for work in a system protection device test or the like.

[0002]

2. Description of the Related Art When laying a power cord for work in a system protection device test or the like, a commercially available drum type cord reel is used for AC 200V and 100V.
For 00V, since there is no commercially available drum type cord reel, a 2-core cord is used. Therefore, the workability of laying and removing is poor, and it is necessary to check the presence or absence of the voltage and the polarity with a DC voltmeter each time the laying is performed, which causes a problem in work efficiency. Further, if AC power is accidentally connected, there is a risk that the DC equipment fed by the work power cord may break down.

[0003]

The problem to be solved by the present invention is to improve work efficiency and safety when laying a DC power cord for work, and to use it without worrying about the polarity error. Another object of the present invention is to provide an automatic polarity matching type DC power cord capable of stopping power supply and protecting equipment even if AC is accidentally connected.

[0004]

In order to solve the above-mentioned problems, an automatic polarity matching type DC power cord of the present invention is a drum support frame and a power cord winding rotatably attached to the drum support frame. A drum barrel is provided, and a DC voltage of the correct polarity is output to the output side, regardless of the polarity of the DC power source on the input side, between the input terminal and the output terminal that receive power by the power cord wound on the drum support frame. An automatic polarity matching circuit for doing so and an AC output prevention circuit for stopping output when AC power is supplied to the input side are provided. The AC output prevention circuit includes a series circuit of an inductor and an electromagnetic switch connected in parallel to an input terminal, and a contact of the electromagnetic switch connected between the input terminal and the output terminal.

Even if the polarity of the input DC voltage is opposite, the polarity is inverted by the automatic polarity matching circuit, and the power of the correct polarity is output to the output terminal. When AC power is erroneously input, the AC output prevention circuit detects AC and prevents power from being output from the output terminal.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below based on Examples. 1 is an external view of an embodiment of the present invention, FIG.
Is a circuit diagram. In FIG. 1, 1 is a drum support frame, 2
Is a winding cylinder, 3 is a winding handle, 4 is a carrying handle, and 5 is a leg. The drum support frame 1 has an input confirmation lamp 6 for displaying the presence / absence of an input voltage, an output confirmation lamp 7 for displaying the presence / absence of an output, an output terminal 8, an output connector 9, and wiring that operates when the output terminal is accidentally short-circuited. The circuit breaker 10 is provided, and as an electric circuit device, as shown in FIG. 2, the inductor 12 and the electromagnetic switch 1 are provided on the input terminal 11 side.
3, a rectifying element 14 is provided. The contacts 13A and 13B of the electromagnetic switch 13 are provided on the power supply line.

Operating Principle a. The reason why the polarity of the output voltage is constant In FIG. 3A, when a (+) DC voltage is connected to the input terminal T1 and a (−) DC voltage is connected to T2, a current flows in the direction of arrow A1. The terminal T3 becomes (+) and T4 becomes (-). On the contrary, when a (-) DC voltage is connected to the input terminal T1 and a (+) DC voltage to T2 as shown in FIG. 3 (b), a current flows in the direction of arrow A2 and the output is also output. The terminal T3 becomes (+) and T4 becomes (-). Thus, the output terminal has a constant polarity regardless of the polarity connected to the input terminal.

[0008] b. Interlock at AC Input In FIG. 4A, when a DC power supply is connected to the input terminals T1 and T2, most of the input voltage is applied to the electromagnetic switch 13 because the voltage drop due to the inductor 12 is small. The electromagnetic switch 13 operates to output a voltage to T3 and T4. However, when an AC power supply is connected to the input terminal, as shown in FIG. 4B, since the voltage drop due to the inductor 12 is large, most of the input voltage is applied to the inductor 12 and the terminal voltage of the electromagnetic switch 13 is increased. Becomes small and cannot operate, and no voltage is output to T3 and T4.

Characteristic Test Results (1) Automatic polarity matching circuit (bridge diode 400
V, 20A) output voltage characteristic test result by load

[Table 1] Thus, the voltage drop due to the rectifying element is very small and can be ignored.

(2) Measurement result of voltage sharing between inductor and electromagnetic switch at DC input and AC input Inductor (R = 66.3Ω, L = 22.94H), electromagnetic switch (R = 210.3Ω, L =) 1.4H)

[Table 2] In this way, the terminal voltage of the electromagnetic switch is very small and does not operate during AC input.

[0011]

As described above, according to the present invention, the following effects can be obtained. (1) The work DC power cord can be easily installed and removed, and the work time can be shortened. (2) Since the work of checking the voltage and polarity by the DC voltmeter after the installation of the DC power cord for work can be omitted, the work can be saved. (3) The polarity of the DC voltage will not be mistaken, so equipment and test equipment There is no danger of damaging. (4) If an AC power supply is accidentally connected, no power will be output, so there is no risk of damaging the equipment and you can work with peace of mind.

[Brief description of drawings]

FIG. 1 is an external view of an embodiment of the present invention.

FIG. 2 is a circuit diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the operation of the automatic polarity matching circuit of the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the operation of the AC output prevention circuit according to the embodiment of the present invention.

[Explanation of symbols]

1 drum support frame, 2 winding drum, 3 winding handle, 4 carrying hand, 5 legs, 6 input confirmation lamp, 7 output confirmation lamp, 8 output terminal, 9 output connector, 10
Circuit breaker, 11 input terminals, 12 inductors,
13 electromagnetic switch, 13A, 13B contact of electromagnetic switch 13, 14 rectifying element

Claims (2)

[Claims] 1. A drum supporting frame, and a power cord winding cylinder rotatably attached to the drum supporting frame, wherein an input terminal and an output for receiving power by a power cord wound on the drum supporting frame. An automatic polarity matching circuit that outputs a DC voltage with the correct polarity to the output side regardless of the polarity of the DC power source on the input side, and an AC that stops the output when AC is fed to the input side. An automatic polarity matching type DC power cord that is equipped with an output prevention circuit. 2. An AC output prevention circuit comprises a series circuit of an inductor and an electromagnetic switch connected in parallel to an input terminal, and a contact of the electromagnetic switch connected between an input terminal and an output terminal. The automatic polarity matching type DC power cord according to claim 1.