Safety devices for elevators 4 9 Electrical safety prot […]
Safety devices for elevators 4
9 Electrical safety protection
Safety protection measures must be taken for the electrical installations and lines of the elevator to prevent electric shock and equipment damage. According to the requirements of GB 7588-1995, the elevator shall adopt the following electrical safety protection measures.
(1) Direct contact electric protection. Insulation is a basic measure to prevent direct contact and electrical short circuits.
(2) Protection against indirect contact with electricity. Indirect contact electricity refers to the electric shock caused by exposed conductive parts of the electrical equipment that is charged when people are in normal contact, such as metal shells, metal conduits, and trunking. In the power supply system where the neutral point of the power supply is directly grounded, the most commonly used protective measure to prevent indirect contact with electricity is to electrically connect the exposed conductive parts of the electrical equipment that may be charged during a fault with the neutral point of the power supply transformer.
(3) Electrical fault protection. According to regulations, AC elevators should have power phase sequence protection, motors and lighting circuits directly connected to the power supply should have short-circuit protection, and motors directly connected to the power supply should also have overload protection.
(4) Electrical safety devices. Electrical safety devices include: directly cutting off the safety contacts of the drive host power contactor or intermediate relay; not directly cutting off the safety contacts of the above-mentioned contactor or intermediate relay and contacts that do not meet the requirements of safe electric shock. But when the elevator electrical equipment fails, such as no voltage or low voltage; the wire is interrupted; the insulation is damaged; the component is short-circuited or open; the relay and the contactor do not release or attract; the contacts do not open or close; when the phase and phase errors are equal , The electrical safety device should be able to prevent the dangerous state of the elevator.