Discussion on the Application and Design Ideas of EI Control Transformer in Elevator Control

Usually, a static electromagnetic device that transforms electrical energy and transfers it from one circuit to another is called a transformer. The control transformer is mainly responsible for converting electricity in the power grid into multiple sets of output voltages. Elevators usually refer to special lifting equipment that uses electricity.

Elevator control hardware generally consists of air switches, relays, frequency converters, brakes, reactors, transformers, etc. The control transformer is responsible for the voltage supply of each control circuit required for the elevator. EI type transformers are the most widely used control transformers in the elevator field. With the increasing demand for elevator product safety, the design requirements for EI type transformers are also becoming higher.

1、 Application of EI Transformer in Elevator Control

(1) Application in the main circuit of elevator drive control

At the input end of the elevator power supply, it is necessary to connect the power supply from outside as an electric drive. Due to the large voltage fluctuations in the power grid and the high current in the power grid circuit, it is impossible to directly supply elevator motors as driving power from the power grid. Therefore, it is necessary to control transformers as voltage for voltage conversion. The EI type transformer has low cost and high reliability, so the control transformer generally adopts the EI type transformer with a capacity of 3KVA to 70KVA, which is connected by DY or YY to convert the voltage in the power grid. The output side of the transformer is connected in series with the air switch and connected to the elevator drive main circuit, thereby controlling the transformer to achieve the voltage supply of the required drive control main circuit for the elevator, isolating the power grid and the elevator control main circuit, and effectively protecting the elevator components from harmonics and sudden short circuit impacts from the power grid.

(2) Application in Elevator Function Control Circuit

The microcomputer control system is currently the mainstream of elevator control systems, and its advantages are very obvious and irreplaceable compared to previous relay control and programmable controller control. The method of microcomputer controlled elevators is to divide the control circuit of elevators into different functional control circuits based on the requirements of elevator functions

In response to this situation, in order to achieve power supply for different functional control circuit loads, it is necessary to control the transformer to convert the voltage of the elevator main circuit power supply to the voltage required for different functional control circuits of the elevator. The functional control circuits of general elevators include door motor control circuit, brake control circuit, safety 36V lighting circuit, safety circuit, floor display and button circuit, etc.

The control transformer applied in the elevator function control circuit has a capacity of less than 3KVA, an output voltage of 36V~220V, and B-level insulation. EI type transformers have the advantages of simple structure, low loss, high insulation, easy to form large-scale production, and low cost. Therefore, they occupy the majority of the share in this small elevator control transformer, which not only meets the power supply requirements of the elevator functional control circuit, but also effectively prevents mutual interference between the main circuit and the functional control circuit.