JPH11259149A - Burning prevention device for electric equipment determining its rated output by period - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a burning preventing device prepared for electric device equipment with its rated output determined by a period and capable of preventing the electric equipment from being used over its rating without requiring a worker to manage application time and extending the service life of the electric equipment. SOLUTION: A current flowing in an output cable 5 is detected by a shunt 30, an average current I in each unit time Δt is obtained and unit calorific value Zi (I<2> .Δt) is calculated by an arithmetic unit 25. Then the sum ΣZ of values Zl to Zk (where k=K/Δt) is compared with an allowable heating value Q (L<2> ×α×K) determined by a rated current value L, a rated utilization ratio αand a period K respectively set up by setting devices 21 to 23 in each unit time Δt, and when ΣZ>Q, a signal from a torch switch 7 is cut off. When the length of a standstill period is set up in accordance with the sum ΣZ of continuous time up to a standstill of the device, the electric equipment can be utilized almost up to its full rating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing burning of an electric device, such as a power supply device for welding, whose rated output is determined by a period.

[0002]

2. Description of the Related Art In a power supply device for welding, for example, a rated current value L and a rated use rate α are determined in order to prevent burnout of device parts due to overload.
For the minute. That is, when the rated current value L is 35
In the case of a power supply device having 0 A and a rated use rate α of 60%, the total time that can be welded at a current value of 350 A in any 10 minutes is 6 minutes, and the remaining 4 minutes must not be used.
Therefore, when the welding is to be performed at the current value I, the operator obtains the allowable usage rate β of the current value I by Expression 1, and
The work was performed such that the welding time per minute did not exceed the allowable usage rate β. β = (L / I) ² × α Equation 1 Therefore, when welding at a current value of 300 A using the above-described power supply device, it is calculated by calculation that the allowable usage rate β is 81%, and welding is performed for 8 minutes. I had to rest for two minutes.

[0003]

However, the management performed by the worker is voluntary and is not always performed. Moreover, even if the allowable usage rate is exceeded, the power supply device does not immediately burn out. For this reason, the power supply device may be used under overload, and the life of the power supply device is shortened.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, to prevent a worker from using the electric device beyond its rating without managing the use time, and to prolong the life of the electric device. It is an object of the present invention to provide a burnout prevention device for an electric device that determines a rated output that can be performed by a period.

[0005]

In order to achieve the above object, an invention according to claim 1 includes a setting device for a rated current value, a setting device for a rated usage rate, a setting device for a period, and a current detector. , A computing device, a storage device, and a timer, wherein the sum of the squares of the detected current values is shorter than the period set by the setting device, and the square of the rated current value and the rated usage rate are used. An output stop signal is output when a product of the period and the time is exceeded.

According to a second aspect of the present invention, in the first aspect, the output stop period is determined according to the sum of the squares of the current values in a predetermined period until the output stop signal is output. It is characterized by the following.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is an external connection diagram in a case where a device for preventing burnout of an electric device according to an embodiment of the present invention which determines a rated output by a period is applied to a power supply device for welding. In the figure, reference numeral 1 denotes a power supply device for a consumable electrode type DC arc, with a rated current value L of 350 A, a rated use rate α of 60%, and a period K.
Is 10 minutes. A fan 2 cools the inside of the power supply 1. Reference numerals 3 and 4 are external output terminals. Reference numeral 5 denotes an output cable on the positive side, which connects the external output terminal 3 to the wire 6. A torch switch 7 is mounted on the torch 8. 9 is a welding load and 10 is a base material. An output cable 11 on the minus side connects the external output terminal 4 and the base material 10. Reference numerals 12 and 13 denote torch switch cables, which are connected to a control unit (not shown) of the power supply device 1 via a switch 28.

Reference numeral 20 denotes a burnout prevention device, 21 is a setter for a rated current value L, 22 is a setter for a rated use rate α, and 23 is a setter for a period K, which are connected to a storage device 24. An arithmetic unit 25 is connected to the storage device 24. Reference numeral 26 denotes a timer, which is connected to the storage device 24, the arithmetic device 25, and the integrator 27. The integrator 27 integrates the voltage output from the shunt 30 and outputs the integrated value M to the arithmetic unit 25 every unit time Δt (here, 0.5 seconds). Reference numeral 28 denotes a double switch. One switch is connected to the torch switch cables 12 and 13 on the contact a side, and the other switch is connected to the alarm lamp 29 on the contact b side. Reference numeral 30 denotes a shunt, which is arranged between the external output terminal 3 and the output cable 5, and outputs a voltage corresponding to a current flowing inside.

Next, the operation of this embodiment will be described. FIG. 2 is a flowchart showing a control procedure. The rated current value L, the rated usage rate α, and the period K of the power supply device 1 are set in advance by the setting devices 21 to 23 and stored in the storage device 24 (procedure S100 in FIG. 2). Here, L = 35
0, α = 60 and K = 10 are input. When a setting completion button (not shown) is turned on, the switch 28 is turned on, and the arithmetic unit 25 determines the allowable amount Q (where Q = L ² × α × K) and the order corresponding to the amount of heat generated during the period K. i
(In this case, since the unit time Δt is 0.5 seconds, imax = 1200) is calculated (step S110). Next, the order i of i is set to i = 0, and Z _{1 to} Z ₁₂₀₀ described later are all set to 0 (step S120).
The process waits for the output of the integral value M (step S130). When the switch 28 is turned on, the torch switch 7 can be operated.

When the integrated value M is output from the integrator 27,
The average voltage at the unit time Δt is obtained and converted into the average current value I to obtain the unit heat generation Z (where Z = I ² × Δt; here, Z = 0.5 × I ² ) (step S140). Then, after adding 1 to the order i (procedure S150), i>
1200 (step S160), i ≦ 12
Immediately if 00, and i = 1 if i> 1200
(Step S170), and Z _i = Z (step S170).
180). Next, the sum ΣZ of the unit heat generation values Z _{1 to} Z ₁₂₀₀ is compared with the allowable amount Q (step S190). If ΣZ ≦ Q, the process of step S130 is performed. If ΣZ> Q, the process of step S3 is performed.
00 is performed.

In step 300, the switch 28 is turned off. Then, the alarm lamp 29 is turned on, and the torch switch 7 cannot be operated. Next, the successive 6
Total heat amount B ₆ per minute (sum of unit heat generation amounts Z _i from i = i−721 to i = i. 720 is a value obtained by 6 minutes × 60 seconds / minute ÷ 0.5 seconds / time) . The same applies hereafter), and the calculated value is compared with 0.95Q (step S310), and B ₆ >
In the case of 0.95Q, the pause time T is set to 4 minutes (procedure S
320), the process of step S330 is performed. In addition, B ₆ ≦
For 0.95Q, compared to 0.95Q by calculating the total heat B ₇ consecutive 7 minutes of the time immediately before (Step S34
0), if B ₇ > 0.95Q, the pause time T is set to 3 minutes (procedure S350), and the process of procedure S330 is performed.

In the case of B ₇ ≦ 0.95Q, the total heat quantity B ₈ for eight consecutive minutes immediately before this point is calculated to obtain 0.9.
Compared with 5Q (procedure S360), if B ₈ > 0.95Q, the pause time T is set to 2 minutes (procedure S370), and the process of procedure S330 is performed. If B ₈ ≦ 0.95Q, the total heat amount B ₉ for the continuous 9 minutes immediately before this point is calculated and compared with 0.95Q (step S380), and B ₉ > 0.
In the case of 95Q, the pause time T is set to one minute (step S39).
0) If B ₉ ≦ 0.95Q, the pause time T is set to 0.5 minute (step S400), and the process of step S330 is performed.

In step S330, the switch 28 is turned on again after waiting for the time t from when the switch 28 is turned off to pass the pause time T (step S410), and the procedure S120 is performed.
Is performed.

[0014] In the case in the procedure S310 i <720, the sum of Z ₁ to Z _i and _{Z 1200-i + 1 ~Z 1200} .
Step S340, Step S360, if steps S380 are similarly calculates the sum of the unit heating value Z _i of contiguous just before stopping.

In the above, when the total amount of heat ΣZ becomes equal to the allowable amount Q, the downtime is determined according to the immediately preceding total amount of heat, so that no useless downtime occurs and the rating of the electric device is reduced. Almost 100% can be used.

In the above description, the rated current value L, the rated use rate α, and the period K can be set. For example, the power supply device 1 has a rated current value of 500 A, a rated use rate of 60%, and a period of 10 minutes. In addition, the rated current value excellent in operability is 350
A, even when the rated use rate is 70% and the period is 10 minutes, that is, when the torch 8 having a smaller rating than the power supply device 1 is connected and welding is performed at a welding current of 300 A, the rating of the torch 8 is reduced. If the rated current value L, the rated use rate α and the period K are set together, the torch 8 can be prevented from being burned without exceeding the rating of the torch 8.

In the above description of the embodiment, the unit time Δt is set to 0.5 seconds.
May be longer.

The pause period may have a fixed length.

Further, a buzzer may be used instead of the alarm lamp 29, or a pause period may be displayed.

Further, the burnout prevention device 20 may be incorporated in the welding power source 1. In this case, the set values of the rated current value L, the rated usage rate α, and the period K may be fixed.

[0021]

As described above, according to the present invention,
If the sum of the squares of the detected current values exceeds the product of the square of the rated current value and the rated usage rate in a period shorter than the period specified by the electric device, an output stop signal is output. With such a configuration, it is possible to prevent a worker from using the electric device beyond its rating without managing the use time, and to prolong the life of the electric device. Further, since the output stop period is determined according to the sum of the squares of the current values in the predetermined period until the output stop signal is output, the pause period can be set to an appropriate length. .

[Brief description of the drawings]

FIG. 1 is an external connection diagram when a burnout prevention device according to an embodiment of the present invention is applied to a power supply device for welding.

FIG. 2 is a flowchart showing a control procedure according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 5 output cable 7 torch switch 21, 22, 23 setting unit 25 arithmetic unit 30 shunt

Continued on the front page (72) Inventor Hidenori Tateishi 2100 Kamimaizumi, Ebina City, Kanagawa Prefecture Hitachi Seiko Co., Ltd.

Claims (2)

[Claims] 1. A setter for a rated current value, a setter for a rated usage rate, a setter for a period, a current detector, an arithmetic unit,
A storage device and a timer, wherein the sum of the square of the detected current value is shorter than the period set by the setting device, and the product of the square of the rated current value, the rated use rate, and the period is obtained. A burnout prevention device for an electric device, which is configured to output an output stop signal when the output exceeds the limit, wherein a rated output is determined by a period. 2. The output stop period according to claim 1, wherein the output stop period is determined according to the magnitude of the sum of the squares of the current values in a predetermined period until the output stop signal is output. A burnout prevention device for electrical equipment whose rated output is determined by period.