Due to incorrect use or unreasonable setting environment, the inverter may malfunction or malfunction, or it may not meet the expected operation results. In order to prevent problems before they occur, it is especially important to carefully analyze the cause of the failure in advance.
External electromagnetic induction interference
If there is interference source around the inverter, they will invade the inverter through the radiation or power line, causing the control loop to malfunction, causing abnormal operation or shutdown, and even damage the inverter in severe cases. It is important to improve the anti-interference ability of the inverter itself. However, due to the limitation of the cost of the device, it is more reasonable and necessary to eliminate the interference source by taking noise suppression measures on the outside. The following measures are specific methods for implementing the “three noes†principle for noise interference: all the relays around the inverter and the control coil of the contactor need to be equipped with absorption devices to prevent the surge voltage, such as RC absorbers; Wiring distance and separation from the main line; the specified shielded circuit should be carried out according to the regulations. If the line is long, a reasonable relay method should be adopted; the grounding terminal of the inverter should be carried out according to the regulations, not the same as electric welding and power. Grounding is mixed; a noise filter is installed at the input of the inverter to avoid interference introduced by the power supply line.
Installation Environment
The frequency converter is an electronic device device and has detailed requirements for installation and use environment in its specifications. Under special circumstances, if these requirements are not met, the corresponding suppression measures must be adopted as far as possible: vibration is the main cause of mechanical damage to electronic devices. For vibration shocks, vibration and other measures should be taken; Gas and dust will cause rust, poor contact, and low insulation of the electronic device to form a short circuit. As a precautionary measure, the control panel should be treated with anti-corrosion and dustproof, and a closed structure; temperature is the life and reliability of the electronic device. Important factors, especially for semiconductor devices, should be installed in accordance with the environmental conditions required by the device or to avoid direct sunlight.
In addition to the above three points, it is also necessary to regularly check the air filter and cooling fan of the inverter. For special high-cold occasions, in order to prevent the microprocessor from working properly due to low temperature, necessary measures such as setting a space heater should be taken.
Abnormal power supply
Power supply abnormalities are manifested in various forms, but they are roughly classified into the following three types, namely, phase loss, low voltage, power failure, and sometimes their mixed forms. Most of the main causes of these anomalies are caused by wind, snow, and lightning strikes, and sometimes due to short-circuit to ground and phase-to-phase short circuit in the same power supply system. Lightning strikes vary greatly by region and season. In addition to voltage fluctuations, some power grids or self-generating units also have frequency fluctuations, and these phenomena sometimes appear repeatedly in a short period of time. In order to ensure the normal operation of the equipment, the power supply of the inverter is also required.
If there is a direct start motor and induction cooker nearby, in order to prevent the voltage drop caused by the input of these devices, it should be separated from the inverter power supply system to reduce the mutual influence; in the case of requiring continuous operation after the instantaneous power failure, in addition to selecting the appropriate In addition to the price of the inverter, due to the pre-consideration of the speed ratio of the load motor. The inverter and the external control loop adopt the instantaneous stop compensation mode. When the voltage is restored, the overcurrent is prevented by the speed tracking and the detection of the speed measuring motor. For the equipment that requires the necessary amount of operation, the inverter should be automatically installed. Switched uninterruptible power supply unit.
The diode input and the inverter using the single-phase control power supply can continue to work in the phase loss state, but the current of the individual components in the rectifier is too large and the pulse current of the capacitor is too large. If the long-term operation will be used, the life and reliability of the inverter will be long. Cause adverse effects, should be checked and dealt with as soon as possible.
Lightning strike, inductive lightning
The surge voltage formed by lightning strikes or induced lightning strikes can sometimes cause damage to the inverter. In addition, when the vacuum circuit breaker is provided on the primary side of the power supply system, the opening and closing of the short circuit can also generate a high surge voltage. When the primary side vacuum circuit breaker of the transformer is disconnected, a high voltage surge spike is formed by coupling on the secondary side.
In order to prevent overvoltage damage caused by the surge voltage, it is usually necessary to apply a snubber such as a varistor at the input end of the inverter to ensure that the input voltage is not higher than the maximum voltage allowed during the main circuit of the inverter. When using a vacuum circuit breaker, an additional RC surge absorber should be formed by impact. If there is a vacuum circuit breaker on the primary side of the transformer, the inverter will be disconnected before the vacuum circuit breaker is operated in the control timing.
In the past, transistor inverters have the following disadvantages: easy to trip, not easy to restart, and low overload capability. Due to the rapid development of IGBT and CPU, the inverter has improved the self-diagnosis and fault prevention functions, which greatly improves the reliability of the inverter.
If the "automatic torque compensation function of the whole field" in the vector control inverter is used, the cause of failure such as "insufficient starting torque" and "decreased output due to environmental conditions" will be well overcome. This function uses the high-speed calculation of the microcomputer inside the inverter to calculate the torque required at the current time, and quickly corrects and compensates the output voltage to offset the change in the output torque of the inverter caused by changes in external conditions.
In addition, since the software development of the inverter is more perfect, various fault prevention measures can be set in the inverter in advance, and the fault can be maintained after the fault is resolved, for example, restarting the motor during the free stop; The internal fault is automatically reset and maintained continuously; when the load torque is too large, the running curve can be automatically adjusted to avoid the trip; the abnormal torque of the mechanical system can be detected.
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