Variable frequency drives (VFDs) are becoming increasingly popular due to the operating efficiency they offer. However, variable frequency drives can create undesirable harmonic effects if not properly supplied. If these effects are left unchecked, they can interfere with neighboring equipment, reducing their productive life or even damaging it. They may also negatively impact your utility provider’s power quality, resulting in penalties. Passive harmonic filters can help, but they tend to reduce effectiveness at loads less than 100%, those offsetting one of the advantages of using a VFD. Adaptive passive technology, on the other hand, maintains strong harmonic filtering performance across a wide range of loads.
Understanding Harmonic Effects
Any modern electrical equipment with embedded microprocessors and electronic circuitry has the potential to create a nonlinear load that will produce harmonics. These harmonics, in turn, create non-sinusoidal line currents in the form of electrical pulses which distort current and voltage, adding strain to electrical systems. As harmonics are reflected onto the utility grid and accumulate, they can interfere with the power quality. This can impact your bottom line since large commercial and industrial facilities typically enter into a utility contract that often has financial penalties for lack of compliance with the provider’s harmonic limits.
How Do You Know If You Have Harmonics?
You may need to call on an expert to see if your equipment is producing harmonics, but there are some warning signs to look out for. If you occasionally experience some unexplained occurrences such as flickering lights, alarms going off, and circuit breakers and earth leakage protection devices tripping for no apparent reason, you are most likely experiencing harmonics in your electrical environment. Harmonics can cause equipment to run hot, so if you find hot cables, hot switchboards, or overheating motors, harmonics may be causing stress on your equipment. In the long term, harmonics degrade an electrical system, resulting in damage and the need to replace equipment before its expected life span––costing you money. The presence of harmonics also means that a large percentage of the power you are being supplied may be unusable.
Mitigation Devices Can Help Reduce Harmonics in Variable Frequency Drives
All variable frequency drives can create harmonics in electrical systems. Harmonic mitigation devices can be used on both the input side and output side of a VFD to minimize the effects of harmonics. In a recent test, a 6-pulse VFD from Advanced Industrial Devices with a harmonic filter using adaptive passive (AP) technology outperformed an active front end (AFE) drive in a number of important areas. The addition of the MTE Matrix AP device resulted in improved harmonic performance under balanced line conditions as well as imbalance conditions, and had similar performance for loads ranging from 50 to 100%, unlike the results of an 18 pulse or AFE drive. In addition, the 6-pulse drive with the Matrix AP harmonic filter offers smaller equipment size, lower price, shortened lead time, and increased availability of drives and corresponding replacement parts when compared to the 18 pulse or AFE drive.
The challenges involved in addressing harmonics can be confusing. That’s where the experts at AID can help.
AID has been in business for more than 35 years and brings over 100 years of product and application knowledge of motors and VFD systems. As a result, we have the expertise to help you mitigate harmonics issues while providing a VFD system that can help optimize your process and increase reliability. We’ll make sure you get the best use of your equipment for years to come.