Suppliers of frequency converter supporting equipment remind you that improper use of frequency converters not only fails to fully utilize their excellent functions, but may also damage the frequency converter and its equipment, or cause interference effects. Therefore, the following precautions should be taken during use:
1. The frequency converter must be selected correctly.
2. Carefully read the product manual and follow the instructions for wiring, installation, and use.
3. The frequency converter device should be reliably grounded to suppress radio frequency interference and prevent electric shock caused by leakage of the frequency converter.
4. When using a frequency converter to control the speed of an electric motor, the temperature rise and noise of the motor will be higher than when using grid electricity (power frequency); When operating at low speeds, due to the low speed of the motor fan blades, attention should be paid to ventilation and cooling, as well as appropriately reducing the load, to prevent the temperature rise of the motor from exceeding the allowable value.
5. The impedance of the power supply line cannot be too small. When the frequency converter is connected to the voltage grid, if the capacity of the distribution transformer is greater than 500KVA, or if the capacity of the distribution transformer is greater than 10 times that of the frequency converter, or if the frequency converter is connected very close to the distribution transformer, due to the small circuit impedance, a large surge will be generated on the frequency converter at the moment of input, which will damage the rectifier components of the frequency converter. When the impedance of the line is too low, an AC reactor should be installed between the power grid and the frequency converter.
6. When the three-phase voltage imbalance rate of the power grid is greater than 3%, the peak value of the input current of the frequency converter will be very large, which can cause overheating of the frequency converter and its connections or damage to electronic components. At this time, it is also necessary to install AC reactors. Especially when the transformer is connected in a V-shape, it is more serious. In addition to installing a reactor on the AC side, a DC reactor also needs to be installed on the DC side.
7. Excessive capacitors should not be installed on the incoming side to improve the power factor, nor should capacitors be installed between the motor and the frequency converter, otherwise it will cause a decrease in line impedance, resulting in overcurrent and damage to the frequency converter.
8. Compensation capacitors cannot be connected in parallel on the output side of the frequency converter, nor can capacitors be connected in parallel to reduce high-order harmonics of the output voltage of the frequency converter, otherwise it may damage the frequency converter. In order to reduce harmonics. Can be connected in series with reactors.
9. The starting and stopping of motors regulated by frequency converters should not be directly operated by circuit breakers or contactors, but should be done using the control terminals of the frequency converter. Otherwise, it may cause the frequency converter to lose control and potentially lead to serious consequences.
10. It is generally not advisable to install AC contactors between the frequency converter and the motor to avoid overvoltage during the interruption period and damage to the inverter. If installation is required, the output contactor should be closed before the frequency converter runs.
11. For situations where a frequency converter drives a regular electric motor for constant torque operation, long-term low-speed operation should be avoided as much as possible, otherwise the motor's heat dissipation effect will deteriorate and the heating will be severe. If it is necessary to operate at low speed and constant torque for a long time, a variable frequency motor must be selected.
12. For situations where the load is increased and there is frequent start stop, there will be torque generated, and appropriate braking resistors need to be selected, otherwise the frequency converter will often trip due to overcurrent or overvoltage faults.
13. When the motor has a brake, the frequency converter should operate in a free stop mode, and the braking action signal should only be issued after the frequency converter issues a stop command.
14. The blocking of the external braking resistor of the frequency converter cannot be less than the requirement of the braking resistor allowed by the frequency converter. On the premise of meeting the braking requirements, the braking resistor should be larger. Never short-circuit the terminal that should be connected to the braking resistor directly, otherwise a short circuit accident may occur through the switch tube during braking.
15. When the frequency converter is connected to the motor, it is not allowed to use a megohmmeter to measure the insulation resistance of the motor, otherwise the high voltage output by the megohmmeter will damage the inverter.
16. Properly handle the issues of acceleration and deceleration. The acceleration and deceleration time set for the frequency converter is too short, which may cause damage to the frequency converter due to electrical shock. Therefore, when using a frequency converter, if the load equipment allows, the acceleration and deceleration time should be extended as much as possible.
① If the load is heavy, the acceleration and deceleration time should be increased; On the contrary, the acceleration and deceleration time can be appropriately reduced.
② If the load equipment needs to accelerate or decelerate in a short period of time, it is necessary to consider increasing the capacity of the frequency converter to avoid excessive current exceeding the rated current of the frequency converter.
③ Si l'équipement de charge nécessite une accélération et une décélération rapides (inférieures à une seconde, par exemple), un système de freinage doit être prévu sur le convertisseur de fréquence. Généralement, les convertisseurs de fréquence de grande capacité sont équipés de systèmes de freinage.
17. Éviter les points de résonance mécanique des dispositifs de charge. Les moteurs électriques peuvent rencontrer des points de résonance mécanique d'équipements dans une certaine plage de fréquences, ce qui entraîne une résonance mécanique et perturbe le fonctionnement du système. Il est donc nécessaire de définir une fréquence de coupure (ou fréquence d'évitement) pour le convertisseur de fréquence et de la dépasser afin d'éviter les points de résonance.
18. Avant la première utilisation du moteur ou avant toute utilisation prolongée avant son raccordement au convertisseur de fréquence, il est impératif de mesurer sa résistance d'isolement (à l'aide d'un mégohmmètre de 500 V ou 1 000 V ; la valeur mesurée ne doit pas être inférieure à 5 MΩ). Une résistance d'isolement trop faible risque d'endommager le convertisseur de fréquence.
19. Le convertisseur de fréquence doit être installé verticalement, avec un espace de ventilation laissé, et la température ambiante doit être contrôlée pour ne pas dépasser 40 ℃.
20. Des mesures anti-interférences doivent être prises pour empêcher le convertisseur de fréquence d'être affecté par des interférences et d'affecter son fonctionnement normal, ou pour empêcher les harmoniques d'ordre élevé générées par le convertisseur de fréquence d'interférer avec le fonctionnement normal d'autres appareils électroniques.
21. Veillez à la protection thermique du moteur électrique. Si la puissance du moteur est compatible avec celle du variateur de fréquence, la protection thermique intégrée à ce dernier assure une protection efficace du moteur. Dans le cas contraire, il est nécessaire d'ajuster les valeurs de protection ou de prendre d'autres mesures de protection afin de garantir le fonctionnement sûr du moteur.
La valeur de protection thermique électronique du convertisseur de fréquence (détection de surcharge du moteur) peut être réglée dans une plage de 25 % à 105 % du courant nominal du convertisseur de fréquence.