First, the inverter harmonics overview The frequency converter is a typical six-pulse rectifier device, therefore, it is a source of high harmonics, the harmonic content of the inverter on the output side, can be measured up to 70% The current distortion rate seriously affects the safe operation of other electrical appliances. In recent years, it has been found that in the case of using multiple inverters, the damage rate of the power module of the inverter is rapidly increased, and the cause of the damage is not found. Sometimes, the inverter will inexplicably fail, but after the shutdown is restarted, the fault disappears. There are many phenomena such as "faults", and the reason is the influence of harmonics.
According to the relevant standards, the harmonic currents of these injected grids need to be suppressed or eliminated to protect the safe operation of electrical equipment.
In 1993, China issued a standard for harmonic management, which stipulated the maximum value of harmonic currents generated by installing, adding or updating electrical equipment that generates harmonics. If any of the first harmonics exceeds the specified limits, the user is required to take remedial measures.
Second, the inverter filter classification Inverter input filter is installed between the input side of the inverter and the power supply, mainly used to suppress the conducted interference and radio interference generated by the inverter, and has the common mode and differential mode suppression capability. It is used to prevent the electromagnetic environment from requiring interference to the power grid and other digital equipment when the inverter is working.
The inverter output filter is installed between the output side of the inverter and the motor. It is mainly used to reduce the high-order harmonic layer in the output current, suppress the surge voltage on the output side of the inverter, and reduce the high-frequency harmonic of the motor. Wave caused by additional torque to reduce motor noise.
The sine wave filter is installed between the output side of the inverter and the motor. It makes the output voltage and current of the inverter approximate to a sine wave, reducing the harmonic domain coefficient of the motor and the insulation pressure of the motor.
3.1. Technical specifications of the inverter filter Installation: indoor, floor or wall; filter connection: cable or bus; filter rated voltage: 3φ400V, 525V, 660V AC; filter rated frequency: 50Hz/ 60Hz; Filtering efficiency: 70%In Power factor: 0.95 Switching frequency: 2-16KHZ Withstand voltage: 3000VAC 10mA for 60 seconds; Filter overload capacity: 1.5 times rated current 1 minute, 3 times / hour Protection level: IP65; Filter Cooling: Natural air cooling or forced air cooling; Filter working conditions: Altitude ≤ 2000m Ambient temperature -25°C~+85°C Relative humidity 90% (+20°C) 3.2, Inverter filter function has good interference Suppression ability: It is placed at the output end of strong interference power electronic equipment such as inverter, which can effectively reduce the electromagnetic interference generated by the equipment.
3.3, the role of the inverter filter: effectively reduce the high-frequency harmonics of the IGBT output; suppress the harmonic interference of the inverter output; suppress dv / dt, extend the life of the motor; protect the drive device power electronic components from the main power peak current impact Reduce main power harmonics and commutation gap; have good interference suppression capability and improve system reliability; 3.4. Use of inverter filter The inverter filter produced by our company is applicable to any brand inverter, power supply, elevator Industries such as Omron Inverter, Yaskawa Inverter, Fuji Inverter, Mitsubishi Inverter, Hitachi Inverter, Siemens Inverter, Danfoss Inverter, Inverter Inverter, LG (LS) Inverter, Fuji Inverter, ABB Inverter , Schneider inverter, Emerson inverter and so on.
The following options can be added to the input side of the inverter: 1) Input Reactor line reactor, input reactor can suppress harmonic current, improve power factor and weaken the surge voltage and current impact on the inverter in the input circuit. To weaken the influence of the power supply voltage imbalance, in general, line reactors must be added.
2) Input EMC filter, the role of EMC filter is to reduce and suppress the electromagnetic interference generated by the inverter. There are two types of EMC filters, Class A and Class B filters. EMCA grade filters are used in the second category of industrial applications and meet the EN50011A standard. EMC Class B filters are mostly used in the first category of applications, namely civil and light industrial applications, to meet the EN50011B standard.
There are several options on the output side of the inverter: 1) Output reactor output reactor. When the cable length of the inverter output to the motor is greater than the specified value of the product, an output reactor should be added to compensate the coupling capacitance when the long cable runs. The charging and discharging effects are avoided to avoid overcurrent of the inverter. There are two types of output reactors. One type of output reactor is a core reactor, which is used when the carrier frequency of the inverter is less than 3KHZ. Another type of output reactor is ferrite type, which is used when the carrier frequency of the inverter is less than 6KHZ. The output reactor is added to the output of the inverter to increase the distance between the inverter and the motor. The output reactor can effectively suppress the instantaneous high voltage generated by the IGBT switch of the inverter, and reduce the adverse effect of this voltage on the cable insulation and the motor. . At the same time, in order to increase the distance between the inverter and the motor, the cable can be appropriately thickened to increase the insulation strength of the cable, and the unshielded cable should be used as much as possible.
2) Output dv/dt filter Output dv/dt reactor. The output dv/dt reactor is used to limit the rising rate of the inverter output voltage to ensure the insulation of the motor is normal.
3) Sinusolidal filters sine wave filter, which makes the output voltage and current of the inverter approximate sine wave, reducing the harmonic domain coefficient of the motor and the insulation pressure of the motor.
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