What are the structural and appearance requirements for inverse-time overcurrent relays?
1. All parts of the relay should be mounted on a fixed, moisture-resistant base and protected by an enclosure to prevent damage from external mechanical forces and the intrusion of external objects. The enclosure should be dustproof, and the operation indicator and setting value should be visible without opening the enclosure.
2. The relay should be designed to be sealed with a lead seal, allowing adjustment or setting only after opening the casing and removing the seal. When the relay is adjusted and shipped from the factory, the relevant parts should be sealed with paint.
3. Relays of the same model should have uniform external structure and installation dimensions, and the interchangeability of easily damaged parts should be ensured.
4. Metal parts in relays should be free from rust, insulating parts should be free from cracks and missing pieces, and the materials used should not cause oxidation or surface damage to contacts and other components.
5. For mechanical position indicators, the indication should clearly represent the position of the action and be restored without opening the housing. For light indicators, the structure should facilitate replacement and inspection.
6. All solder joints must be firm and reliable, without any cold solder joints, and must not cause corrosion to the connecting components. All mechanical and electrical connections of the relay must be firm and reliable, and not easily loosened.
7. When wiring a relay that protrudes from the panel, the length of the wiring screw should take into account the thickness of the panel on which the relay is installed. The thickness of the metal panel is calculated as 5mm.
8. The relay setting mechanism should have a braking or locking device.
9. All electronic components used in relays shall meet the requirements of the corresponding technical standards. Static relays shall be equipped with test terminals (or holes) for checking the voltage levels of key components.
10. The design of printed circuit component mounting shall comply with the provisions of GB1360-78 "Printed Circuit Grid", and the quality of printed circuit boards shall meet the relevant technical standards for printed circuit boards.
11. For pluggable structures, the connectors should have reliable contact and be easy to plug and unplug. Pluggable parts of the same model relay should be interchangeable and meet the relevant technical standards. The pluggable structure should not come into contact with live parts when inserting or removing the plug, and the current terminals should have reliable features to prevent overvoltage when disconnected.
