Analysis of the Influence of Three-phase Unbalanced on AC-AC Elevator System and Fault Symptoms

- Aug 16, 2018-

Three-phase power supply

Three-phase power supply

1: three-phase four-wire system

2: Three-phase five-wire system

Cross---AC frequency conversion requirements for three-phase power supply: three-phase five-wire system

Three phases: A, B, C

Zero line: N

Ground: PE

Elevator power supply

The use of high-tech development in modern equipment, the power supply requirements for power supply is getting higher and higher. In the elevator application of microprocessor-controlled variable frequency drive, the elevator requires three-phase five-wire system for power supply.

In order to make the elevator more comfortable, stable and safer, it is required that the three-phase power supply three-phase must be balanced.

When the three-phase power supply is unbalanced, according to the principle of energy conservation, the voltage vector sum on A B C is zero, and the voltage on the neutral line (neutral line) is offset. Therefore, a voltage potential difference occurs between the neutral line and the ground line.

In the AC-AC variable drive circuit, the three-phase unbalance directly affects the voltage sampling, decoupling, pulse width modulation and phase-correction loop of the VVVF system, affecting the comparison and operation of the given and feedback. Lead to a series of failures

An error will occur in the system decoupling circuit.

Sampling of the supply voltage in the energy feedback system

Error in phase angle sampling and phase synchronization of three-phase power supply in the energy feedback system

Three-phase unbalanced fault code in the presence of OTIS REGEN elevator fault notepad

Distribution of electricity consumption of elevator equipment

Elevator inverter drive motor power

Power consumption of the elevator control system

Elevator lighting power supply

Other elevator air conditioners

Electricity consumption of other elevator communication and monitoring equipment

       If the power consumption of the above equipment is unevenly collected on the A\B\C three-phase, it will lead to three-phase unbalance, which will cause the zero point of the zero line to drift, and the zero line and the ground line will generate a voltage potential.

1: In the vector controlled VVVF drive, the main drive control board will issue a fault reminder "three-phase unbalance" "AC Main Imbalance"

2: In the elevator driven by permanent magnet synchronous host driven by energy feedback, there are many unexplained faults in the control system, such as

 "Converter Id err( Feedback)"

"Converter Iq err(feedback"

 "Converter PLL Open"

 "AC Main Imbalance" (VAC imbanlance)

Single elevator situation

Single elevator drawing wiring design, when the power supply capacity is insufficient.

After the deviation occurs, the system must be uniformly powered, and the lighting power wiring should be phase-shifted at the upper end of the main switch, or the power supply of the elevator air conditioner can be changed to phase wiring.

If the neutral line is left floating, the system will be damaged. Therefore, if the above modifications are made, it must be ensured that the neutral line is not suspended, so as to avoid the existence of parasitic circuits.

The elevator power supply bus capacity is insufficient.

In the power supply of the group-controlled elevator system building, the switch branches in the power supply cabinet of the owner are arranged by the busbars, branching to the power supply of each elevator, and the color sequence of the power supply wiring of each elevator is the same.

If the uniform sequence is used to power the elevators. This will cause problems, we must consider that the power consumption of the A B C three-phase must be basically equal.

Fault check and recovery

1: The wiring capacity of the power supply system must meet the requirements for power consumption.

2: Use the multimeter AC voltage file to measure the AC voltage between the neutral line and the ground line. The voltage value must not be greater than AC25V, and it is better to control it within AC5V.

3: When the single line elevator and the ground line voltage are too high, the system power must be uniformly charged, and the lighting power connection should be phase-shifted at the upper end of the main switch, or the power supply of the elevator air conditioner can be changed. Phase wiring operation.