With the development of science and technology, frequency conversion control is more and more widely used in construction lift. Frequency control of motor speed are characterized by their smooth start-stop process, reduce mechanical shock, increase occupant comfort, improve the service life and other characteristics, but also can be adjusted by changing the power supply frequency speed, save energy, improve work efficiency, but the variable frequency speed regulation system in use process there is interference, tend to cause construction elevator safety accidents.

The inverter system circuit of construction elevator is mainly composed of main circuit and control circuit. The main circuit is mainly composed of rectifier circuit and inverter circuit. The control circuit is mainly composed of microprocessor, PAW trigger, PWM current controller and current feedback.

The interference sources of frequency conversion speed regulation system of construction lift mainly include:

(1) overvoltage, undervoltage, instantaneous power off induction interference;

(2) inrush current induction interference;

(3) peak voltage pulse induction interference;

(4) rain and fog weather when the induction of self-induced current interference;

(5) radio signal interference.

After the frequency conversion speed regulation system of the construction lift is disturbed, the system program will run out of control, resulting in the motor running fast and slow, the hanging cage running up and down the speed is not stable; Make the control fail, the stop button and the emergency stop button do not work, the motor can not stop down and other phenomena, may cause the construction lift out of control or fall high, resulting in safety accidents.

The interference of frequency conversion speed regulation system of construction lift is mainly divided into induction interference and radio signal interference.

Induction interference is caused by electromagnetic induction on the signal line carrying noise resulting in the control equipment misoperation; Radio signal interference is the high frequency electromagnetic wave emitted by the frequency converter itself and the wire, which makes the radio receiver produce noise.

The frequency conversion speed regulation system of construction lift can adopt the measures of anti-induction interference, anti-radio interference and reliable grounding to prevent interference.

(1) measures to prevent inductive interference:

(1) install the energy-saving device on the input side of the inverter

In the input line end of the power supply of the frequency conversion system, additional energy-saving appliances can not only play the role of energy saving, but also can eliminate the interference of power supply fluctuations on the frequency converter.

(2) in the inverter input side access reactor

A series reactor in the input circuit is an effective way to suppress the low harmonic current.

(3) converter output through the steel pipe

Install heater or place desiccant in the control box

In rainy and foggy weather, especially in foggy weather, due to the temperature drop after the element board of the frequency converter stops working, the shift electronic components of the humid air, especially the capacitive and inductive components, will be affected by moisture. When the power is switched on again, the inductive current will be generated, and even the leakage switch will trip. The heater can be set in the control box to remove moisture from the electronic components, but also to prevent the control box from absorbing moisture in the air, so as to ensure the electrical components dry.

(2) the main measures to prevent radio interference include:

(1) install a filter on the output side of the inverter

The function of the filter is to suppress the interference signal by the inverter through the line transmission interference, weaken the higher frequency harmonic components. This kind of filter mainly has the line filter and the radiation filter two kinds.

(2) shielding interference source.

(3) reliable grounding

Reliable grounding is often an important means to suppress noise and prevent interference. A good grounding method can prevent interference signal intrusion and improve the anti-interference ability of the system.