JP2844866B2 - Internal pressure explosion-proof surge pack - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal pressure explosion-proof surge pack installed adjacent to an explosion-proof electric motor used in industry and protecting the electric motor against surge overvoltage.

[Prior art]

If there is a sudden change in the circuit state in the power system, an electromagnetic transient (surge phenomenon) occurs. An abnormal voltage generated in the power system due to this transient phenomenon is called a surge overvoltage. Surge overvoltage is the most important factor that affects the insulation design and insulation coordination of various devices and lines in the power system. Typical surge overvoltages in power systems are shown below. (A) Lightning surge A surge generated by a lightning strike, which is a very steep overvoltage with a time to a peak of several μs and a surge duration of about several tens of μs. (B) Disconnector surge This is a sudden surge that occurs when a bus is opened and closed by a disconnector, but is generally smaller than a lightning surge. (C) Switching surge This is a surge that occurs when the circuit breaker is switched, and almost disappears within several cycles of the commercial frequency. (D) Accident surges The typical surges that occur at the time of a line accident are a ground fault surge and a ground fault interruption surge. The former is an overvoltage that occurs immediately after a ground fault, and the latter is an overvoltage that occurs when the ground fault is disconnected from the power supply by a circuit breaker. Industrial explosion-proof motors are each connected to a system power supply, but arresters, surge capacitors, or both are used to protect against surge overvoltages generated from the system power supply. A device in which these protection devices are housed in a box and integrated as a unit is called a surge pack. This surge pack is usually installed near the electric motor. By forming the surge protection device against surge overvoltage into a surge pack, the surge pack can be installed close to the motor, and the motor can be protected against surge overvoltage without being affected by disturbance such as lightning. However, conventionally, although there is an explosion-proof structure standard for electric motors, there is no explosion-proof structure standard for surge packs. The explosion-proof structure standards for electric motors are as follows. Electric motors have explosion-proof construction standards for electrical machinery and equipment (September 1972
The Ministry of Labor Notification No. 80) is stipulated as follows. The explosion-proof structure is a fully closed structure, in which a flammable gas or a flammable liquid vapor enters the inside of a container and causes an explosion. Refers to a structure that does not ignite gas or vapor outside the The internal pressure explosion-proof structure uses air,
A structure in which a protective gas such as nitrogen gas or carbon dioxide gas is fed or sealed to prevent gas or vapor from entering the inside of the container. The safety-enhanced explosion-proof structure is a component that constitutes an electric machine and does not emit sparks or arcs when the electric machine is normally energized under a rated load or less.
Alternatively, it refers to a structure in which the insulation performance and the safety against danger due to an increase in temperature and external damage are improved for those which are not likely to become an ignition source due to high temperature.

[Problems to be solved by the invention]

In places where there is a danger of ignition or explosion, the pressure in the section where the motor is installed is made higher than the outside air by instrumentation air. When there is a danger of a fire explosion in the installation place of the electric motor, the explosion-proof structure is required to be applied not only to the electric motor but also to the surge pack. When the surge pack is installed adjacent to the electric motor in such a place, an explosion-proof structure or an internal-pressure explosion-proof structure is selected. However, a surge pack having an explosion-proof structure requires a separate blower to maintain the internal pressure by filling air from the blower into the surge pack, which is expensive, and requires time and effort to maintain the blower. The present invention provides a surge pack that can easily maintain an internal pressure without requiring a special air blower and easily manage equipment when a surge pack installed adjacent to an explosion-proof electric motor is an internal pressure explosion-proof type. The purpose is to provide.

[Means for Solving the Problems]

The above object is achieved by disposing an explosion-proof electric motor in a space where the pressure in a section is higher than the outside air by instrumentation air, and installing the explosion-proof electric motor adjacent to the explosion-proof electric motor so as to protect the explosion-proof electric motor against surge overvoltage. This is achieved by providing the internal pressure explosion-proof type by branching, decompressing and enclosing the instrumentation air in the surge pack.

[Operation]

According to this invention, it is installed adjacent to the explosion-proof electric motor used in the space where the pressure is higher than the outside air by the instrumentation air,
Since the internal pressure of the surge pack is increased by branching, decompressing and enclosing the instrumentation air into a surge pack that protects the explosion-proof electric motor against surge overvoltage, the internal pressure of the surge pack is reduced without requiring a ventilation device. Can be maintained, and device management can be facilitated.

【Example】

An explosion-proof electric motor is arranged in a place where there is a danger of ignition or explosion and the pressure inside the compartment is higher than the outside air by instrumentation air. Is installed. An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a longitudinal sectional view of an internal pressure explosion-proof surge pack according to an embodiment of the present invention, and FIG. 2 is a view taken in the direction of arrow II in FIG. First
In FIG. 2 and FIG. 2, a lightning arrester 2 and a surge absorbing capacitor 3 are connected to three terminals 4 in a cover 1.
Inside, 5 kg / cm ² of instrumentation air is branched and 50 m
Reduce the pressure to about mAq. The air depressurized through the pressure reducing valve 5 is supplied from the bottom of the surge pack through a pipe 6. The three terminals 4 are connected to the cable of the explosion-proof motor by the lead wire 8 outside the cover 1 of the surge pack. Monitoring of the internal pressure of the surge pack uses a pressure detector for the lower limit of the internal pressure.
7a and a pressure detector 7b for the upper pressure limit are used. The lower one is used to maintain the internal pressure explosion-proof function, and the upper one is installed to prevent surge pack damage. The pressure detectors 7a and 7b use, for example, differential pressure micro switches. When a surge overvoltage occurs in the system to which the cable of the explosion-proof motor is connected, the surge overvoltage is absorbed by the surge arrester 2 and the surge absorbing capacitor 3 in the surge back, thereby protecting the explosion-proof motor.

【The invention's effect】

The present invention provides a surge pack that protects an internal pressure explosion-proof motor against surge overvoltage, branches instrumentation air provided at a place where the motor is installed to increase the pressure in the compartment from outside air, and reduces the pressure. Since it is sealed by filling, the internal pressure of the surge pack can be easily maintained. Moreover, the internal pressure of the surge pack can be easily monitored by the pressure detector. The internal pressure explosion-proof surge pack according to the present invention does not require a special air blower, so that equipment costs and maintenance of the air blower are not required, and labor can be saved. According to the present invention, an explosion-proof electric motor can be protected from a surge overvoltage in a small space.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an internal pressure explosion-proof surge pack according to an embodiment of the present invention, and FIG. 2 is a view taken in the direction of arrow II in FIG. 1: cover, 2: lightning arrester, 3: condenser for surge absorption, 4:
Terminal, 5: pressure reducing valve, 6: piping, 7a, 7b: pressure detector, 8: lead wire.

Claims (1)

(57) [Claims] An explosion-proof motor is disposed in a space in which the pressure in a section is higher than the outside air by instrumentation air, and is disposed adjacent to the explosion-proof motor so as to protect the explosion-proof motor against surge overvoltage. In the installed surge pack,
An internal pressure explosion-proof type surge pack, wherein the instrumentation air is branched, decompressed and sealed into the surge pack to form an internal pressure explosion-proof type.