Key points for Maintenance of Inverter

Danfoss is the first inverter manufacturer in the world. As a prestigious European brand, Danfoss’s inverter, with a series of advantages like excellent speed control performance, wide speed control range and high operating efficiency, convenient to operate and easy to access to other equipment, have been widely accepted by users since entering Chinese market and applied to many industries like textile, printing and filling production line. During application of inverter, various inverter faults may appear. Therefore, improving the technological level for troubleshooting inverter fault based on the self-diagnosis function of the inverter will greatly reduce the inverter fault handling time. Our company specializes in manufacturing viscose staple fibre and more than 200 Danfoss 5000 series of inverters have been applied to our production line. During use, many inverter fault alarm appear due to environment conditions (temperature, humidity, corrosive gas, etc.). Over the years, we insist in studying and exploring during practice and have accumulated a lot of experience in fault maintenance and daily maintenance & service. Daily maintenance personnel must be familiar with basic working principle and function features of the inverter and master basic knowledge about electrician operation. Before executing daily inverter maintenance, make sure to cut off the main power completely and wait for 5 to 30 min(according to the inverter power) after the inverter lamp is completely off. Besides, pay attention to checking network voltage, improving surroundings of inverter, motor and wires, removing dust inside the inverter on a regular basis and strengthening equipment management so as to reduce the fault rate of inverter to the greatest extent.

(1) Cooling fan

Inverter power module is most likely to get hot and the heat generated due to continuous operation must be discharged timely. The service life of fan is generally 20kh to 40kh. Consider continuous operation of the inverter, fan shall be replaced every three to five years to avoid fault caused by poor heat dissipation.

(2) Filter capacitor

Intermediate circuit filter capacitor, also known as electrolytic capacitor, is mainly used to smooth DC voltage, absorb DC low-frequency harmonic . The heat generated during continuous operation and that generated by the inverter will accelerate drying of electrolyte and has a direct effect on its capacity. Under normal condition, the service life of the capacitor is five years. Therefore, it is recommended to check capacitor capacity once a year regularly and replace it when the capacity reduces by more than 20%. In addition to maintenance, carefully check the inverter, power on it regularly, make the inverter works with motor at 2hz low frequency for 10min so as to ensure normal operation of the inverter.

(3) Use of anti-corrosive agent

Due to our production feature, there is excessive concentration of corrosive gas in all electrical mcc room in our company, causing electrical equipment damages due to corrosion (including inverter). To solve this problem, we have specially installed a set of air-conditioning system to take advantage of fresh air to improve environment conditions. Moreover, in order to reduce corrosion of corrosive gas to elements of the printed circuit board, we also require inverter manufacturer to carry out anti-corrosion treatment against printed circuit boards and spray anti-corrosion agent to it after maintenance. In this way, inverter fault rate is reduced effectively and efficiency is improved.

With higher scientific and technological level, the inverter combines with strong current and weak current. Improper use or accidental events may cause damages to the inverter. To ensure normal operation of the inverter and less fault, there is a higher demand on the technical level of maintenance personnel and it is necessary that technical maintenance personnel has a full understandings about field environment, equipment and process. The above statements are based on my experience accumulated during inverter usage and maintenance. All test instrument said in this document is fluke 177 multimeter. Individual parameters may be different for pointer gauge. We are looking forward to discussing with colleagues to give you some reference. If there is anything inappropriate, please make a comment or criticism.