Matters needing attention when evaluating the elec

When evaluating the electrical equipment of the crane - precautions

in order to avoid the serious consequences caused by the failure of the electrical equipment of the crane in the process of installation, use and maintenance, the following precautions should be paid attention to when evaluating the electrical equipment of the crane

I. General requirements

1 The electrical equipment of the crane must ensure accurate and reliable transmission performance and control performance, and can immediately cut off the power supply in case of emergency. Do not change the circuit arbitrarily during installation, maintenance, adjustment and use to avoid the failure of the safety device

2. The installation of crane electrical equipment must comply with the relevant provisions of the code for construction and acceptance of electrical device installation engineering

II. Power supply and circuit

1 The crane shall be powered by a dedicated feeder. For AC 380V power supply, if soft cable is used for power supply, a core wire should be prepared as the grounding wire; If the sliding line is used for power supply, a special grounding sliding line, namely four sliding lines, should also be provided for occasions with high safety requirements

2. The main circuit breaker shall be set at the incoming end of the special feeder of the crane. The outgoing terminal of the main circuit breaker shall not be connected to other equipment unrelated to the crane

3. The main circuit breaker shall be set on the crane. In case of short circuit, it shall have the function of breaking the circuit. The main circuit breaker cannot be set on the small single beam crane operated on the ground

4. The main line contactor shall be set on the crane, which shall be able to disconnect the power circuit or control circuit of all mechanisms. When the air head of the main mechanism has been set on the crane, the main line contactor may not be set

5. The crane control circuit shall ensure that the control performance meets the requirements of the mechanical and electrical system, and there shall be no wrong circuit, parasitic circuit and false circuit

6. Any mechanism controlled by the remote control circuit and automatic control circuit shall automatically stop working in case of control failure

7. On the AC crane, the overweight electromagnet shall be equipped with a special DC power supply system and a standby power supply if necessary

8. Safety requirements for bare sliding wire of power feed: all parts of the power supply and equipment shall be free of defects Ψ Occlusive ridge ǎ To print Σ Take care of it)? The contact surface of the sliding wire should be flat without rust, with good conductivity and proper installation. Compensation devices should be set when crossing the expansion joints of buildings;? The main sliding wire of power supply shall be painted with red paint on the non-conductive contact surface, and safety signs or indicator lights indicating electrification shall be installed at appropriate positions

9. The crane must adopt copper core multi strand conductor. Rubber insulated wires and cables are generally used as conductors. When using multi strand single core copper wire, the cross-sectional area should be> =1.5mm2; When using multi strand and multi-core copper wires, the cross-sectional area should be> =1.0mm2. There are no regulations on the cross-sectional area of connecting wires that can confirm the safety and reliability of electronic devices, servo mechanisms, sensor elements, etc

plastic insulated wires can be used for the wiring inside the electrical room, control room, control panel and protection box, as well as the small cross-sectional area wires of the main circuit and the wires of the control circuit

ship cables should be used for cranes working in ports

10. For cable powered cranes, when the moving distance is more than 10m, cable drums or other retracting devices should be set. The cable retracting and releasing speed shall be synchronized with the crane running speed

11. Safety requirements for electrical wiring: it shall be free from noise, and it shall be free from noise Ψ Please read the description of the risks in the water supply system of the water supply system of the people's Republic of China. Please check the water supply system of the water supply system of the people's Republic of China, and be sure to use the water supply system of the people's Republic of China? For cranes working indoors, their wires should be laid in trunking or metal pipes, and the cables can be laid directly. Protective measures should be taken in places with mechanical damage, chemical corrosion or oil erosion.? Wires of different mechanisms, different voltage levels, AC and DC shall be separated when threading; Lighting wires shall be laid separately

III. safety requirements for main electrical components

electrical components should be compatible with the mechanism characteristics, working conditions and environmental conditions of the crane. When working under rated conditions, the temperature rise shall not exceed the rated allowable value. If the working conditions and environmental conditions of the crane change, the electrical components should be changed accordingly

1. Dust shall be removed at any time during automatic start to prevent the same flashover; The automatic start should be checked and maintained frequently to ensure that the contacts are in good contact and the terminals are firmly connected

2. Contactors should be checked and repaired frequently to realize the localization of high-end products as soon as possible; Optimize the industrial structure of the stone cone to ensure that the action is flexible and reliable, the end face of the iron core is clean, the contact is smooth and flat, and the contact is close, so as to prevent adhesion and jamming. The reversible contactor shall be checked regularly to ensure reliable interlocking

3. The action value of overcurrent relay and time delay relay shall be adjusted according to the design requirements, and the contact shall not be arbitrarily short circuited

4. The controller shall be flexible in operation, clear in gear and zero position, and reliable in operation; During the maintenance of the controller, the positioning element shall not be removed arbitrarily

the action direction of the operating handle or handwheel should be consistent with the action direction of the mechanism

the upright handle shall be equipped with a protective device to prevent the circuit from being connected due to accidental collision

5. The armature of the brake electromagnet shall act flexibly and accurately without blocking, and the contact surface of the iron core shall be in close contact without abnormal sound. The middle air gap of the electromagnet shall meet the original design requirements

IV. electrical protection device

1 Start of main isolation. The main disconnector should be used at the incoming line of the crane; The small single beam crane operated on the ground may not be set

2. Emergency power failure starts. The crane shall be equipped with an emergency power-off switch, which can cut off the main control power supply of the crane in an emergency. The emergency power-off switch shall be set at the most convenient place for the driver to operate

3. Short circuit protection. It's not easy ψ Bar zhixia Feili words Di nephew keep out numerous; ぃ? When the mechanical mechanism of the crane is driven by the cage asynchronous motor, the short-circuit protection shall be set separately

4. The crane must be equipped with voltage loss protection and zero position protection

5. Loss of excitation protection. It is necessary to pay attention to the following aspects: ι Fang Т Malaria; ぃ? DC powered energy consumption braking and eddy current brake speed regulation system shall be equipped with loss of excitation protection

6. Overcurrent protection. You must make sure that you are in charge of the business; However, Guangdong Province has detected the problems of the toner industry and the development of the industry? Three phase wound motor can be set with overcurrent protection in two phases, so as to ensure the accuracy of impact test and prolong the service life of equipment. The system protected by the protection box should be set with total overcurrent breaker protection on the third phase of the motor;? DC motor can be protected by an overcurrent relay

7. Overspeed protection. The main lifting mechanism of the crane for casting and quenching, as well as the lifting mechanism and luffing mechanism of the crane adjusted by silicon controlled stator pressure regulation, eddy current brake, energy consumption braking, silicon controlled power supply and DC unit power supply, shall have overspeed protection

8. Grounding. Yongdim section В Haoshan MUE offers all kinds of products, such as "Pu Fu MUE" and five kinds of products, which are all owned by the company τ It's a good place to be Ρ 3. The paper supports itself? Grounding structure: the crane metal should have reliable electrical connection. The crane working on the track can generally be grounded through the wheel and track. If necessary, special grounding sliding wire for equipment or other effective measures should be adopted; The grounding wire shall be connected by flat steel with a cross section of> =150mm2 or copper wire with a cross section of> =10mm2, and shall be connected by welding; It is strictly forbidden to use the grounding wire as the current carrying zero line.? Requirements for grounding of lifting electromagnets: during this period, the Soviet Union also developed some corresponding high-tech alloys for lifting electromagnets powered by AC rectification, and their shells must have reliable electrical connections with cranes.? Grounding requirements for suspended control button box: there must be a reliable electrical connection between the metal shell of the county suspended control button box and the crane

9. Grounding resistance and insulation resistance. The enterprise has its own electronic equipment, so it has its own electronic equipment= 4 ohms.? AC power supply voltage of main circuit and control circuit