Troubleshooting VFD Harmonics in Motor Drive Systems
Variable frequency drives (VFDs), which are found in nearly every modern industrial facility, are used to control the speed of motors in many systems. VFDs play a role in pumps, conveyors, fans, compressors, and more. VFDs help save energy and can even extend equipment life by reducing mechanical wear and tear. Their role makes them an important part of many Canadian industries.
However, VFDs can create harmonic distortion. These unwanted electrical frequencies can have many consequences, including reduced equipment life and increased electrical noise. When this problem occurs, electromechanical technicians are often the first workers to notice and troubleshoot the problem. If you're interested in becoming an electromechanical technician, you too will need to know how to recognize and troubleshoot these problems. Having this information can help you build your skills and your career.
What Are Harmonics?
In an ideal electrical system, the fundamental frequency is 60 hertz. Harmonics are currents and voltage waveforms that operate on frequencies that are multiples of the fundamental frequency. These frequencies distort the fundamental frequency, causing it to become choppy.
As harmonics increase, the choppiness becomes more severe. VFDs are a common source of harmonics, and when multiple VFDs operate together in one facility, their harmonics combine and contribute to the total harmonic distortion.
How VFDs Create Harmonics
VFDs are considered non-linear loads, which means they don't draw power in a smooth voltage waveform. They also draw current in pulses. These characteristics mean that VFDs naturally produce harmonics that can affect equipment nearby. Because VFDs naturally produce harmonics, they must be monitored and managed to ensure their harmonics are minimized.
Signs and Symptoms of Harmonic Problems
There are many symptoms of harmonic problems. As an electromechanical technician, you'll have to watch for some of the following:
- Motor noise
- Vibration
- Electrical fires
- Overheating (motors, transformers, cables, etc.)
- Timing errors
- Nuisance breaker tripping
- Flickering lights
Erratic operation of electronic equipment
Over time, trouble with harmonics can lead to reduced motor life and complaints about the quality of the power being produced. Catching these problems early can help ensure the facility runs smoothly.
Measuring and Identifying Harmonics
Analyzing and measuring the harmonics in the system helps ensure good power quality and prevents equipment damage. Using quality meters is important for identifying harmonics.
Taking a step-by-step approach to diagnosing harmonic issues is important for consistently identifying and addressing problems. It's also important to take measurements from the right location. Measuring at different points in the area helps determine whether a single drive is the problem or if the problem comes from the total number of drives in the vicinity.
Practical Solutions to Harmonic Problems
There are many ways to mitigate problems with harmonic solutions. Choosing the best solution for the application is always important, as is performing proper installation. Experienced electromechanical technicians must know how to implement solutions to ensure the best results.
Line Reactors
A line reactor is an electromagnetic device made up of steel wrapped with copper coils. The coils form a magnetic current that limits the inrush current, reducing the peak. This rounds the waveform and helps minimize distortion, often to 30%.
Passive Harmonic Filters
Passive harmonic filters block certain harmonic frequencies. Analyzers use tools to identify which harmonics require filtering and then place the filters in locations where they will be most efficient.
Non-linear Load Upgrades
Sometimes the easiest way to reduce distortion is to replace VFDs with models that create less distortion. Analyzing the equipment status can help determine whether this is a good solution for the facility.
Phase Balancing
Balancing the load across the phases can help reduce distortion. A power analyzer can be used to detect imbalanced loads in multiphase systems. This information can be used to help balance the load.
Active Harmonic Solutions
Active harmonic filters are designed to adapt to changing harmonics. These devices can filter out multiple harmonic frequencies simultaneously, canceling harmonics in real time. Active filters cost more than passive filters but can be helpful in certain contexts.
How Electromechanical Technicians Can Help
Electromechanical technicians play an important role in identifying harmonic issues. An experienced electromechanical technician will have the skills to troubleshoot and mitigate these problems. Technicians work with a range of other professions and industries, including engineers and utilities, to help improve/reduce harmonics in modern automated facilities.
Training Pathways and Career Opportunities
Harmonics are a problem for modern industrial facilities, so these facilities require well-trained technicians to troubleshoot, apply solutions, and reduce harmonics to ensure that equipment runs efficiently. If you're interested in a career in manufacturing, utilities, and automation, electromechanical technician training provides a path forward.
Effective training in power quality knowledge starts with a trusted polytechnic program.
Solving Harmonics Starts Here
Understanding harmonics helps make technicians more valuable to utilities and automation facilities. Getting the right training is important to start your career as an electromechanical technician. If you're interested in working on advanced machinery in automation facilities, and if harmonics interests you, then the next step is clear.
Start by contacting a program consultant at George Brown Polytechnic toll-free at 1-888-553-5333 or email at [email protected], or follow this link to discover the skills you can develop in the Electromechanical Technician program Our training program can help you get started with an in-demand career that puts you at the forefront of modern automation.