Elevator use the elevator inverter issues

    With the power thyristor (SCR) power transistor (GTR) and the new field-effect transistor (IGBT) have come out, frequency conversion technology from the 1960s appeared so far has matured universal use in various electric fields. Elevators and other special mechanical and electrical equipment is no exception, the drive also makes the technical content, performance is leaps and bounds, with the traditional way of comparing the effect of speed is fresh obviousness see. It makes the elevator efficiency, smooth running, extend equipment life, combined with a PLC or computer control, but also demonstrate the superiority of non-contact control: Line simplified, flexible control, reliable operation, easy maintenance and fault monitoring. Seen by the elevator inverter works, the installation must meet certain requirements in order to work properly, the elevator inverter itself inevitably produce harmonic interference and electromagnetic radiation and other common problems, but the elevator power is larger, poor working environment, the safety factor requirements high, therefore, led to the elevator inverter in the installation and maintenance of a number of issues.

1, harmonic interference problems
1.1 Interference of the mechanism
    elevator inverter main circuit is generally cross - straight - cross forms, namely rectifier (AC / DC) and an elevator inverter section (DC / AC) component, the first three-phase bridge rectifier power supply, and then by power transistor switching element for DC / AC converter.
    In the input section, the input voltage is a sine wave, nonlinear three-phase bridge rectifier diodes and discrete diode parameters will cause a non-sinusoidal input current waveform. In the output section, the output line voltage is SPWM pulse width modulated square wave, the phase voltage is a step wave, are nonlinear. The output current is nearly sinusoidal with a burr. Since it is a non-linear sine wave, then he will produce harmonics. Theoretically, harmonics multiple of 3 does not contain harmonics and even harmonics, the Fourier series decomposition according to the fundamental and harmonic, and generally contains 6n +1 (n = l, 2,3 ... .) harmonics. Harmonic frequency elevator inverter modulation frequency, which were 5, 7, 11, 13th harmonic current dominant.
1.2 Interference hazards
    Input current harmonic distortion causes the grid voltage, causing the impact on other electrical equipment, such as the transformer temperature rise, resulting in vibration noise; cause protection of electrical malfunction; cause measuring instrument error; insulation damage, affecting the electrical work and reduce life expectancy and so on.
    According to GB12668-90 requirements management standards of higher harmonic voltage integrated grid voltage harmonic distortion is THD% ≤ 10%, odd harmonics THD% ≤ 5%, even harmonics THD% ≤ 2%.
    Both output voltage and current harmonics, the modulation frequency is low, the human ear could hear high harmonic frequencies generated electromagnetic noise (screams), harmonic heat and vibration caused by the motor, the peak voltage or insulation breakdown , reactive big loss, cosφ reduction. Modulation frequency higher harmonics impact should be small, but no matter the level of the modulation frequency, harmonic electromagnetic coupling are formed through the wire inductive interference, and through the cable to the space launch high-frequency electromagnetic radiation interference on the surrounding lines, electrical equipment and other adverse effects, such as interference with the elevator door control signal so that it is not working properly, the computer board LCD error, computer clocks stop working. Under normal circumstances, the elevator inverter output harmonic voltage THD% of total synthesis should be controlled at between 5% to 7%.
1.3 Interference suppression
    Regardless of the input or output harmonic interference caused by nothing more than its mode of transmission line conduction, inductive coupling and air radiation in three ways, so the interference suppression measures we have from several aspects:
    (1) connected reactors and filters. Input access to AC reactor ACL, it 5-9 harmonics suppression effect is very significant, cosφ also be increased to 75% to 85%, the output is generally not connected to the reactor, the reactor when choosing the best drop controlled at 5% or less. Connected in series between the rectifier bridge and filter capacitor DC reactor DCL also markedly inhibited the harmonic currents and improve power factor. Then the power filter should pay attention to: the output side of the filter capacitor connected to the motor side only, and should be connected resistors to prevent the elevator inverter due to capacitor charging and discharging by shock, filter reactor phase connection cable must be in the same direction around the In the same magnetic core to no effect on the fundamental current. Capacity greater than 22KW generally used in parallel when the power supply filter.
2) reasonable shielded cabling and wiring. Use separate transformer elevator inverter power elevator inverter simultaneously use two more to be away from each other; Other equipment and control lines in the layout as far away from the elevator inverter input and output lines (minimum is also more than 10cm), and do not run in parallel with line, the best vertical cross; signal control lines twisted inhibit phase differential mode interference signal; reasonable ground wiring devices harmonic interference suppression also one of the ways, according to state regulations in addition to grounding wire with a grounding wire to ensure sufficient grounding resistance of less than 5Ω, the elevator inverter should be grounded separately, grounding point as close to the elevator inverter, ground wire away from power lines can not be connected and the power of the zero line; pair of main circuit (elevator inverter to the motor cable) for wear metal tube shield, and as short as possible, control signal lines can also be used shielded cable, shielded cable should be close to the side of the elevator inverter control circuit is connected to the COM terminal, while the shield grounded at one end only.
    (3) Other equipment interfere with isolation transformer on the grid for power supply isolation, with photocoupler isolation disturbed signal.
    (4) may also reduce the carrier frequency relative to eliminate the interference, but the noise might be a little bigger, the current waveform smoothness to be satisfactory, the specific site commissioning OK. I encountered appeared in the elevator debug the door harmonic interference signal error, the carrier frequency between 8 ~ 10K reduction in the value of the appropriate troubleshooting.
    (5) can also be used when necessary, zero-phase-sequence reactance, surge absorber and surge suppressors.