How to maintain the frequency converter and which parts to replace regularly
I.before the frequency converter is powered onThe temperature and humidity of the surrounding environment should be detected first. If the temperature is too high, the frequency converter will overheat and alarm. If the temperature is too high, it will directly lead to damage to the frequency converter power components and a short-circuit in the circuit. If the air is too humid, direct internal short circuit of the frequency converter may occur. When the frequency converter is running, pay attention to whether the cooling system is producing, such as whether the air duct is exhausted and whether the fan has abnormal sound. Generally speaking, frequency converters with relatively high protection class such as: IP20 or more frequency converters can be directly opened and installed. Frequency converters below IP20 should generally be cabinet-mounted, so the cooling effect of the frequency converter cabinet will directly affect the normal operation of the frequency converter. Exhaust system such as whether the fan rotation is smooth, whether there is dust and obstructions in the air inlet are all parts of our daily inspection. Whether motor reactors, transformers, etc. are overheated or smelly; whether the frequency converter and motor have abnormal noises; whether the frequency converter panel current display is too large or the current change range is too large, and whether the output UVW three-phase voltage and current are balanced.
Regular dust removal Check if the air inlet of the fan is blocked. Clean the air filter cooling air duct and internal dust every month.
Regular inspections should be conducted once a year: Check whether screws, bolts, and plug-ins are loose, and whether there is a short-circuit between the input and output reactors and the inter-phase resistance. Normally, it should be more than tens of megaohms. Conductors and insulators are subject to corrosion. Clean up with alcohol if necessary. Measure the smoothness of the output voltage of the switching power supply, such as: 5V, 12V, 15V, 24V and other voltages. Whether the contacts of the contactor have spark marks, serious replacement of new contactors of the same type or larger than the original capacity; confirmation of the correctness of the control voltage, sequential protective action test; confirmation of protection display circuit no abnormality; The balance of the output voltage when frequency converter operating alone.
Conscientiously do the routine maintenance and repair of frequency converter, including:
Do a good job in the daily maintenance of the frequency converter and its maintenance work, the contents mainly include:
- Dust removal from the frequency converter is carried out regularly, focusing on the rectifier cabinet, frequency converter cabinet and control cabinet. If necessary, the rectifier module, frequency converter module and circuit board inside the control cabinet can be removed and dust can be removed. Frequency converter under the air inlet, outlet air outlet is dirty or blocked by excessive dust. Since the frequency converter requires a large amount of ventilation due to its own heat dissipation requirements, after a certain period of operation, the dust on the surface area is very serious and the dust must be regularly cleaned.
- Open the front door of the frequency converter and open the rear door. Carefully check whether the AC/DC busbars are deformed, corroded, oxidized, and whether the screws at the connection of the busbars are loose or not. With the insulation sheet or insulation column with or without aging cracking or deformation, if there should be promptly replaced, re-fastened, the deformation of the busbar must be corrected and re-installed.
- After removing dust from circuit boards, busbars, etc., perform necessary anti-corrosion treatment and brushing insulating paint. After the busbars that have undergone partial discharge or arcing are to be removed, their burrs must be removed. Insulation boards that have been broken down by insulation must be removed from their damaged parts, insulated with corresponding insulating grades of insulation plates in the vicinity of their damage, fastened and tested for insulation and considered qualified before being put into service.
- Check whether the fans in the rectifier cabinet and the inverter cabinet are running and rotating normally. When they are stopped, turn them by hand to observe whether the bearings are stuck or noisy. If necessary, replace the bearings or repair.
- a comprehensive inspection of the input, rectifier and inverter, DC input fast-melting, found that burned and replaced in a timely manner.
- Whether the capacitor in the intermediate direct current loop is leaking, whether the shell is inflated, bubbling or deformed, and whether the safety valve is broken. It is possible to test the capacitance capacity, leakage current, withstand voltage, etc. of the condition, which does not meet the requirements. Capacitors are replaced, and new capacitors or capacitors that have been unused for a long period of time must be passivated before replacement. Filter capacitor life cycle is generally 5 years, the use of time in more than 5 years, capacitance, leakage current, pressure and other indicators significantly deviate from the detection criteria, should be partially or completely replaced as appropriate.
- Conduct electrical tests on the rectifying and inverting diodes and GTOs with a multimeter, determine their forward and reverse resistance values, and make careful records in the pre-formulated table to see if the inter-pole resistance is normal. The same model of device consistency is good, if necessary, replace it.
- Inspect the main contactors and other auxiliary contactors in the A1 and A2 inlet cabinets. Observe carefully whether the contactors of the contactors have arcs, burrs, or surface oxidation and irregularities. The replacement of the static and dynamic contacts ensures that the contact is safe and reliable.
- Carefully check whether the terminal block of frequency converterhas aged or loosened, whether there is a hidden short circuit fault, whether the connection lines are firmly connected, whether the line skin is damaged, and whether the plugs of the circuit boards are firmly connected. Access to the main power line connection of frequency converteris reliable, there is no connection to the phenomenon of thermal oxidation, grounding is good.
- Does the reactor of frequency converterhave abnormal sounds, vibrations or smells?
In addition, the filtered DC waveform, inverted output waveform, and input power harmonics of frequency converter can be measured conditionally.
III.replacement of spare parts of frequency converter
Frequency converter consists of many components, some of which will gradually reduce and age after long-term operation. This is also the main reason for frequency converter failure. In order to ensure the long-term normal operation of the equipment, the following components should be replaced periodically:
1. cooling fan of frequency converter
The power module of the frequency converter is a device with serious heat generation. The heat generated by continuous operation must be discharged in time. The life of a typical fan is approximately 10kh to 40kh. According to the continuous operation of the frequency converter converted to 2~3 years, the fan should be replaced. The direct cooling fan has two points and three lines. One of the two line fans is positive and the other line is negative. Do not connect wrong when replacing; There is a test wire outside the negative electrode. Please pay attention when you replace it, otherwise it will cause the frequency converter to overheat and alarm. AC fans are generally 220V, 380V points, do not make mistakes when changing the voltage level.
2.filter capacitor of frequency converterIntermediate DC loop filter capacitor: also known as electrolytic capacitor, its main role is to smooth the DC voltage, absorb the low frequency harmonics in the DC, the heat generated by its continuous work plus the heat generated by the frequency converter will speed up the drying of its electrolyte, It directly affects the size of its capacity. The service life of the capacitor under normal conditions is about 5 years. It is recommended to check the capacitance once a year at regular intervals. Generally, a new filter capacitor should be replaced when its capacity is reduced by more than 20%.