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Compared with flameproof electrical equipment, safety-enhancing electrical equipment has the advantages of simple structure, convenient maintenance and low cost, so it is widely used in coal mines, but the explosion-proof performance of safety-enhancing electrical equipment is worse than that of flameproof electrical equipment. Therefore, the correct use and strengthening the maintenance and management of safety-enhancing electrical equipment in coal mines is an important link to ensure the explosion-proof performance of safety-enhancing electrical equipment and give full play to its efficiency.

Safety-enhancing electrical equipment, maintenance

Compared with flameproof electrical equipment, safety-enhancing electrical equipment has the advantages of simple structure, convenient maintenance and low cost, so it is widely used in coal mines, but the explosion-proof performance of safety-enhancing electrical equipment is worse than that of flameproof electrical equipment. Therefore, the correct use and strengthening the maintenance and management of safety-enhancing electrical equipment in coal mines is an important link to ensure the explosion-proof performance of safety-enhancing electrical equipment and give full play to its efficiency.

First, the use of increased safety electrical equipment

In order to ensure that the explosion-proof performance of increased safety electrical equipment meets the requirements, the following aspects should be paid attention to during installation and use.

1 Keep the protection level of the shell not lower than the standard.

1. 1 Handle with care during transportation to avoid collision.

1.2 The on-site support for installation and use shall be reliable to prevent coal gangue from hitting the equipment.

1.3 The shell exposed outside the charged body must be fastened with special fasteners, and the shell can only be opened with special tools.

1.4 The rubber gasket used for sealing on the shell must be intact, and any damage or aging that affects the sealing performance must be replaced.

1.5 The protective paint of the shell must be intact.

2 Wire connection

2. 1 All wire connections (connection between lead and terminal, wire connection in winding, etc.) must take reliable measures (such as double-wire connection). ) To prevent accidental sparks and arcs such as poor contact, open welding, disconnection and the like caused by vibration, overload, startup and other reasons during the operation of the equipment, and have sufficient mechanical strength. The wiring mode needs the correct welding process to ensure the welding quality.

2.2 The threads of the conductive screw and nut of the connector must be good, and there must be no shortage of elastic intermediate pieces composed of flat pads and spring pads to prevent looseness between the conductive screw and the insulating seat.

2.3 Wiring must have special gaskets (such as bow pads and tooth pads) to prevent the core wire from cracking. It is best to use wire nose when connecting cables or wires below 4MM2, and copper-aluminum transition joint should be used for aluminum wire connection.

2.4 The air gap and creepage distance between exposed live conductors in the junction box shall meet the requirements.

2.5 If the temperature measuring element with overheating protection is installed in the increased safety motor, the control line connecting the temperature measuring element should avoid the power line terminal as far as possible, and the power line terminal should be separated from the temperature measuring element terminal with a grounded metal partition to prevent the protection circuit from contacting with high voltage.

3 temperature protection device

3.65438+

3.2 Squirrel-cage motor with temperature measuring elements in the winding, when the winding is overhauled, the temperature measuring elements should be buried in the original way.

At the same time, the protection device must determine the protection characteristic curve as the basis for setting the protection device, and the determination of the protection characteristic curve shall meet the following requirements.

A. The temperature measurement shall be started under the cooling condition with the ambient temperature of 20℃;

B the current range is at least 3 ~ 8 times of the rated current;

C. the disconnection time error shall not exceed 20%.

3.3 Conditions of Use of Safety-increasing Motor

Generally speaking, motors with over-current delay protection devices are only allowed to be used for continuous operation with light load starting and infrequent starting. For motors with long starting time or frequent starting, special protection devices must be adopted to ensure that the temperature of the motor does not exceed the maximum allowable temperature.

Second, increase the maintenance of safety electrical equipment.

The daily maintenance and overhaul of mine safety-increasing electrical equipment mainly includes: strengthening the inspection of conductor connectivity, temperature rise of insulation winding, insulation level and parts where sparks or arcs will occur during normal operation, correctly setting and regularly adjusting and testing protection devices.

1 Requirements for protective performance of enclosure

The protective performance of the enclosure of the increased safety electrical equipment is very important to ensure the normal operation of the equipment. During operation, it shall be ensured that the shell protection level of the insulated live part of the increased safety electrical equipment meets the requirements of IP54, and the shell protection level of the exposed live part meets the requirements of IP54, and any phenomenon that may reduce the shell protection performance shall be avoided. If the safety-enhancing electrical equipment is prevented from being smashed, crushed and squeezed, the protective paint of the shell should be repainted if it falls off to prevent the shell from rusting.

2 Inspection and maintenance of junction box

2. 1 Due to the possibility of moisture absorption and dust adhesion on the surfaces of terminals and insulation parts in the junction box, the resistance of insulation surfaces will be greatly reduced, resulting in leakage accidents. Therefore, in daily maintenance, attention should be paid to checking and removing dust and dirt inside and outside the junction box to maintain an appropriate insulation level.

2.2 The threads of terminals and nuts in the junction box must be good. If there is a sliding button, it should be replaced immediately.

2.3 All kinds of connectors must be intact and fastened, and the wire connection must be good. If discoloration is found, it means that the thread end is not pressed and heated, and it must be fastened immediately.

3 Check the parts that generate sparks during normal operation.

Components that generate sparks during normal operation of safety-enhanced electrical equipment (such as slip rings of wound induction motors, lamp holders of lamps, etc.). ) must be installed in a fireproof enclosure. The inspection and maintenance methods of these explosion-proof components should be carried out in the first section of this chapter.

4. Daily maintenance of increased safety motor

The safety performance of the increased safety motor depends on the matching, correct setting and careful maintenance of the protection device. The main contents of daily maintenance of increased safety motor are as follows.

4. 1 Check the three-phase current of the motor frequently to avoid overload operation of the increased safety motor.

4.2 In order to prevent the rotor from being locked in the operation of the increased safety motor, it is stipulated that the protection device should act reliably during the rotor locked time te. Therefore, the protection device must be set strictly according to the tE time value of the motor.

4.3 In order to prevent the friction between the stator and the rotor caused by the small unilateral air gap between the stator and the rotor in the operation of the increased safety motor, the maintenance electrician should check the unilateral air gap with a feeler gauge once a month, and its value should comply with the provisions in Table 4-6. If the air gap is too small, stop the machine immediately.

4.4

In order to prevent sparks between the squirrel cage bars and the rotor core when the squirrel cage motor is started, additional slot lining, slot wedge or other embedding measures can be adopted for a single squirrel cage bar to ensure a light and tight fit between the squirrel cage bar and the rotor. Therefore, when disassembling and overhauling the safety-enhancing motor on the ground, check whether all the slot wedges of the motor are firm, replace the loose slot wedges, and check whether there are any faults such as broken bars, open welding or end ring cracks on the squirrel-cage rotor.

4.5 After overhaul, the safety-increased motor should be tested for insulation strength, and the voltage withstand should be increased by 10% on the basis of national standards.

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