Tag: CONVO VFD

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Global Variable Frequency Drive (VFD) repair center

“Longi Electromechanical” has more than 20 years of experience in industrial control maintenance, and is one of the earliest companies engaged in VFD repair. Equipped with artificial intelligence AI maintenance instruments, it specializes in emergency repair of various equipment, with high technical efficiency. It has repaired more than 200,000 units of equipment, including ultrasonic, robot, charging pile, inverter,Variable Frequency Drive (VFD), touch screen, servo, intelligent instrument, industrial control machine, PLC and other products. General problems can be repaired on the same day. LONGI promises you that “if it can’t be repaired, we won’t charge you”. And it provides lifelong maintenance service and free technical consultation for inspection! For urgent repair consultation, please call the contact number or add WHATSAPP maintenance hotline: +8618028667265 Mr. Guo

From European and American brands to Japanese, Korean, and Taiwanese ones, until various domestic brands, we have repaired countless models and specifications of VFDs. In the process of serving our customers, we have continuously learned and accumulated maintenance experience to enhance our skills. We specialize not only in repairing VFDs but also in summarizing various maintenance experiences, elevating them to a theoretical level. We have published the book “VFD Maintenance Technology” and offered VFD maintenance training, thereby promoting the development of the VFD maintenance industry. Longi Electromechanical Company has repaired VFDs from the following brands:

European and American Brands

ABB drives, SEW drives, LUST VFD, LENZE VSD, Schneider drives, CT drives, KEB VSD, Siemens drives, Eurotherm VFD, G.E. VFD, VACON VSD, Danfoss VFD, SIEI VFD, AB VFD, Emerson VFD, ROBICON VFD, Ansaldo VFD, Bosch Rexroth VSD, etc.

Japanese Brands:

Fuji INVERTER, Mitsubishi INVERTER, Yaskawa INVERTER, Omron INVERTER, Panasonic INVERTER, Toshiba INVERTER, Sumner INVERTER, Tooka INVERTER, Higashikawa INVERTER, Sanken INVERTER, Kasia INVERTER, Toyo INVERTER, Hitachi INVERTER, Meidensha INVERTER, etc.

Taiwanese Brands:

Oulin INVERTER, Delta INVERTER, Taian INVERTER, Teco INVERTER, Powtran INVERTER, Dongling INVERTER, Lijia INVERTER, Ningmao INVERTER, Sanji INVERTER, Hongquan INVERTER, Dongli INVERTER, Kaichi INVERTER, Shenghua INVERTER, Adlee INVERTER, Shihlin INVERTER, Teco INVERTER, Sanchuan INVERTER, Dongweiting INVERTER, Fuhua INVERTER, Taian INVERTER (note: Taian is repeated, possibly a mistake in the original list), Longxing INVERTER, Jiudesongyi INVERTER, Tend INVERTER, Chuangjie INVERTER, etc.

Chinese Mainland brands:

Senlan Inverter, Jialing Inverter, Yineng Inverter, Hailipu Inverter, Haili Inverter, Lebang Inverter, Xinnuo Inverter, Kemron Inverter, Alpha Inverter, Rifeng Inverter, Shidai Inverter, Bost Inverter, Gaobang Inverter, Kaituo Inverter, Sinus Inverter, Sepaxin Inverter, Huifeng Inverter, Saipu Inverter, Weier Inverter, Huawei Inverter, Ansheng Inverter, Anbangxin Inverter, Jiaxin Inverter, Ripu Inverter, Chint Inverter, Delixi Inverter, Sifang Inverter, Geli Te Inverter, Kangwo Inverter, Jina Inverter, Richuan Inverter, Weikeda Inverter, Oura Inverter, Sanjing Inverter, Jintian Inverter, Xilin Inverter, Delixi Inverter, Yingweiteng Inverter, Chunri Inverter, Xinjie, Kemron-Bong Inverter, Nihonye Inverter, Edison Inverter

Other brands:
Migao VFD, Rongqi VFD, Kaiqi VFD, Shiyunjie VFD, Huichuan VFD, Yuzhang VFD, Tianchong VFD, Rongshang Tongda VFD, LG VFD, Hyundai VFD, Daewoo VFD, Samsung VFD, etc.

Longi Electromechanical Company specializes in the maintenance of VFDs and strictly requires its engineers to followlow standard operating procedures. Upon receiving a unit, the engineers carefully inspect its exterior and clarify any fault conditions with the customer before beginning work. Any removed circuit boards are cleaned using ultrasonic cleaning equipment. Repaired circuit boards are coated with high-temperature and high-pressure-resistant insulating paint, dried in a drying machine, and then reinstalled in the VFD, with measures taken to prevent corrosion and interference.

The repaired VFD will undergo a simulated operation with load using a heavy-load test bench to avoid any potential issues that may arise under actual load conditions on site.

When it comes to VFD maintenance, most cases are related to the equipment on site. Sometimes a standalone unit may have been repaired, but it doesn’t work properly when installed on site. In some cases, the problem lies with the system rather than the VFD itself. For such issues, if the customer requests on-site service, we will do our utmost to resolve the problem for them. If the location is far away, such as in another province, we can use tools like video conferencing and phone calls to allow our engineers to remotely diagnose and resolve the on-site issues for the customer.

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Circuit diagram and maintenance skills of CONVO VSD switch power supply

This is the circuit diagram of the switch power supply for the GVF-G type of the CONVO drivers, with a power of 5.5KW and version number 002-E-P00-01 8.6kVA 13A. This circuit is not considered a very classic switch power supply circuit, but it does not mean that it is a poorly performing circuit, and its failure rate is not high in actual operation.

The input of the circuit is approximately 550V DC voltage at both ends of the autonomous DC home energy storage capacitor. The oscillation and driving are carried out using commonly used power chips 38440, which provide the circuit’s starting voltage and current from R40, R41, and Z8. The Z8 voltage stabilization value has not been measured yet, and is estimated to be around 13V. Here, the LED also serves as a power indicator. After the vibration of 3844, the 7-pin power supply voltage of 3844 is established through rectification and filtering circuits such as D13, Dl4, C30, and C31 through the BT winding. At the same time, this power supply also undertakes the functions of output voltage sampling and voltage feedback. After being divided by R1 and R2, it is sent to the 2 pins of 3844 for feedback voltage input. This is different from the voltage feedback method of switch power supply circuits in other brands of frequency converters. Due to the fact that voltage sampling is not directly taken from the secondary power supply branch of the transformer, it can only be considered as an indirect sampling of the output voltage of each channel, so the control strain rate and accuracy are not too high. However, the+18V and -18V power supply of the secondary winding were introduced into the CPU motherboard, and voltage stabilizing links of 7815 and 7915 were added respectively. The circuit was slightly cumbersome, and its power supply performance was correspondingly improved. After the+8V power supply was introduced into the motherboard, 7805 voltage stabilization processing was added as the power supply for the CPU.
The sampling of the switching tube current is obtained from the resistor R37 connected in series with the K2225 source of the switching tube as usual. Sent to the 3-pin current detection terminal of 3844. 1. The feedback component of the internal voltage amplifier is connected between the two pins, which determines the amplification rate of the sampling voltage. The 8-pin is the Vref terminal, which outputs a 5V reference voltage during normal operation, providing a current path for the external R and C oscillation timing components of the 4-pin, ensuring the stability of the oscillation frequency. The 6 pins are pulse output pins, also known as drive output terminals. Introduced into the gate of switch K2225 through R36.
The 24V output power supply not only provides 24V control voltage for the frequency converter control terminal, but also supplies power to two cooling fans. It can be seen that the operating mode of this fan is controlled by the CPU motherboard signal and determined by parameter settings. There are generally three operating modes: running after power on, running during operation, and running when the radiator temperature reaches a certain value.
Maintenance tips: When the switch tube K2225 is damaged due to breakdown, a high voltage impulse is introduced from pin 3 of 3844, which often causes damage to the R5 resistor. The resistor may also have opened or increased in value:

Maintenance tips: When the switch tube k2225 is damaged due to breakdown, 3844 is often damaged simultaneously due to the introduction of high voltage surge from three pins; The r5 resistor may also be open or the resistance value may have increased; Most of the current sampling resistors r37 connected to the source have also been opened. Before replacing the switch tube, it is necessary to conduct a comprehensive inspection. The switch tube k2225 can be directly replaced with k1317 tube.

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Troubleshooting of CVF-G1 type switching power supply for CONVO frequency converter

Received 3 small power machines from Kangwo CVF-G1, all of which had faults due to no output from the switching power supply and no screen display. The IC of the power supply for this machine is 3844B, and I do not have this model of IC at hand. It is impossible that all three machines are damaged by 3844B, right? So start by checking its peripheral circuits.

All switch mode power supplies have the following branches: 1. The power on start branch is often composed of several resistors with larger resistance values connected in series. When powered on, 500V DC is led to the 3844B power supply pin to provide the starting voltage of the switch tube; 2. The positive feedback and working power supply branches are composed of feedback windings and rectifier filtering circuits (some machines are composed of two winding power supply branches, while others are used in combination); 3. The stabilizing branch is usually powered by a secondary 5V power supply branch, which compares the change in 5V voltage with a reference voltage. Its variable is fed back to the 2 pins of the primary 3844B through the optocoupler, but the voltage feedback of this model is taken from the primary.
The conditions for the circuit to vibrate are: 1. The 500V power supply circuit is normal, the 500V DC is added to the drain of the switch through the main winding, and the source of the switch is formed by a small resistance current sampling resistor to form the power supply circuit; 2. The power on startup branch is normal, providing sufficient amplitude of starting voltage (current); 3. Positive feedback and working power supply branches are normal, providing positive feedback voltage (current) and working power supply that meet amplitude requirements; 4. There is no short circuit on the load side, and the short circuit on the load side cannot establish sufficient amplitude of the feedback voltage, so the circuit cannot vibrate. The above circuit can be called an oscillation circuit.
To minimize the fault, the voltage stabilizing branch should be opened to see if the circuit can vibrate. Voltage reduction and regulation power supply should be implemented, and circuits that are susceptible to voltage impact damage should be cut off to ensure safety. If it can vibrate, it indicates that the four branches that meet the vibration conditions are generally normal, and the faulty components of the voltage stabilizing branch can be further investigated. If the vibration still cannot start, it indicates that the fault is in the oscillation circuit. You can search for the four branches mentioned above.
According to the above inspection sequence, the faults in the switching power supply of machines A, B, and C are all in the oscillation circuit. Check that there are no abnormalities in the four branches of machine A and the peripheral components of 3844B. Try replacing a 3845B and the power output is normal. Repair it; Machine B, after switching to 3845B, still cannot vibrate, and all four branch components are normal. After connecting the 300k resistor of the power on starting branch in parallel with the 200k resistor, the power on is restored to normal; Machine C was also damaged for 3844B, and the fault was resolved after replacing it with a new block.
Only the malfunction of machine B is slightly interesting. The analysis is as follows:
On the surface, it appears that the second machine could not detect any faulty parts, leading to difficulties in maintenance. But after reducing the resistance value of the starting branch, it can work normally. Where exactly is the abnormality of machine B? It may be a slight change in the performance of components that leads to changes in electrical parameters, such as a slight decrease in the amplification ability of switching tubes, a change in Q value of switching transformers due to mild moisture, an increase in internal resistance of 3844B output, or a slight variation in resistance capacitance components. Finding and confirming the above reasons is indeed difficult, or there may be one or even multiple reasons involved. But the various reasons mentioned above only lead to one consequence: the switch tube cannot be effectively started, and the circuit cannot vibrate! The solution is to transform the existing state and exert efforts to promote the oscillation of the switching tube. Parallel connection of resistors in the starting branch is the most labor-saving and effective method.
By the way, the starting resistance of the machine is 300k, and with the addition of resistance from other links, the actual starting current applied to the gate of the switching tube is only slightly over 1mA. Although field-effect transistors are voltage controlled devices that theoretically do not absorb current, the charging current of the junction capacitor that can make them conductive is precisely the hard indicator that makes them conductive. From this perspective, field-effect transistors are still current drivers. When the circuit parameters change, the supply current of the original starting branch is not enough to make the switching transistor conductive or even slightly conductive, so the circuit cannot vibrate. By slightly increasing the starting current value, the circuit may start to vibrate. There is a suspicion that the resistance value of the 300k starting resistor is too high. I believe that slightly reducing its resistance value is beneficial and not harmful.

Therefore, an efficient repair method can be taken as follows: check that the switch tube is not damaged, and that the four branches are generally normal. First, conduct a parallel resistance test on the starting branch, and if it fails, switch to 3844B. If it fails again, then focus on carefully checking the circuit. Often, the fault is already resolved in the first or second step.