I. What impact does a motor failure have on a frequency converter?
1. Abnormal current problem
When a motor experiences faults such as winding short circuits, open circuits, or grounding, its electrical characteristics change, which can lead to abnormal current. For example, a winding short circuit can cause a sharp increase in current, while an open circuit or grounding fault can cause unstable current. If these abnormal currents flow into the frequency converter connected to the motor, they may trigger the frequency converter's overcurrent protection mechanism or short circuit protection function, and in severe cases, may even damage the power electronic components inside the frequency converter.
2. Overheating and overload operation
If a motor operates for an extended period beyond its rated load, i.e., under overload conditions, its own temperature will rise. Simultaneously, the heat transferred through the current will cause the connected frequency converter to overheat. The electronic components inside the frequency converter are highly sensitive to temperature; prolonged exposure to high temperatures will accelerate component aging and reduce the frequency converter's lifespan. Furthermore, motor overload will place additional stress on the frequency converter's control system, demanding higher output power and thus exacerbating losses.
3. Vibration and noise issues
The vibration and noise generated by a motor during operation, especially when the motor is damaged or unbalanced, can significantly increase. These physical effects can be transmitted to the frequency converter through connecting components, affecting the contact stability and lifespan of the internal components. Long-term vibration and shock can lead to loose internal wiring and circuit board breakage, causing malfunctions.
4. Maintenance and Care Strategy
To minimize inverter failures caused by motor problems, strict maintenance and upkeep measures must be implemented for the motor. This includes regularly inspecting the motor's physical condition and electrical performance, and promptly replacing or repairing damaged components such as bearings and windings. A reasonable maintenance plan not only ensures the efficient operation of the motor itself but also helps protect the connected inverter from damage.
II. How to Choose a Suitable Frequency Converter
Choose a frequency converter with appropriate performance based on process requirements. Don't blindly pursue high performance, as higher performance comes at a higher price. For example, for frequency converters used in fans and water pumps, a standard sinusoidal pulse width modulation (PWM) frequency converter is sufficient, as fans and water pumps are square torque loads, with torque dropping significantly at low speeds. Furthermore, fans and water pumps do not require high-precision speed control or complex control functions (such as forward and reverse rotation). For compressor control, due to the complex torque characteristics of compressors, especially the large starting torque, a vector frequency converter with good torque characteristics and current limiting function should be selected. For papermaking and chemical fiber equipment, a high-precision, high-response closed-loop vector frequency converter should be chosen. Reliability – the purpose of using frequency converters is to improve production efficiency. If the performance is good but the reliability is poor and problems occur frequently, then the losses outweigh the gains.
Furthermore, the power modules, a key component of frequency converters, now widely adopt IGBT modules and IPM intelligent power modules. IPM modules, in particular, while more expensive, offer significant improvements in reliability due to their internal overcurrent, short-circuit, undervoltage, output grounding, and overheat protection functions. In the event of an anomaly, the module immediately activates its own protection mechanism, followed by secondary protection through external circuitry. This greatly reduces the likelihood of module burnout and significantly enhances reliability. In contrast, products using GTR modules lack built-in protection, and the external protection and drive circuits are complex. If the protection fails to keep up, the module can burn out instantly.
Some manufacturers still use GTR modules to reduce costs, which is something to be aware of when purchasing frequency converters. Price is a major factor to consider when purchasing frequency converters, but if you only pursue a low price, it often leads to a decrease in quality and reliability, because the power devices and main circuit electrolytic capacitors in a frequency converter account for about 70% of the cost.
