Which Solution For Harmonic Attenuation Is Right For You?
For factories and industrial sites, controlling the cost of operations and equipment to protect the margin is a priority. Replacing the equipment ahead of time can increase capital spending by up to 15% and operating costs by up to 10%. Implementing an appropriate harmonic attenuation solution helps avoid such costs.
Harmonics are unwanted currents that overload circuits and transformers, generating heat and sending interference through power lines, which can lead to higher charges. In industrial environments that use many motors, undetected harmonics can reduce equipment life or, at a minimum, weaken equipment reliability. Harmonics can overload the electrical system, increase power demand, damage equipment, and turn off systems.
A Comparison Between Harmonic Attenuation Solutions
AC line reactors and DC coupling coils for actuators help attenuate current flow for variable frequency drives (VFDs) by expanding the flow and reducing the amplitude to partially minimize harmonics. This is the most reasonable priced compact solution, but it is less effective at alleviating total harmonic distortions. This solution is best for applications where harmonic attenuation is not the first priority, but it is necessary to filter out the heavier distortions.
A 12-pulse arrangement is the most efficient way to control power loss and is suitable for larger drives. This solution requires a transformer with phase shift of 30 ° and a 6-pulse bridge converter connected to each of the outputs. The 12-pulse solution is superior in efficiency and harmonic attenuation, but it is neither simple to deploy nor the least-priced option.
A passive filter consists of reactors and capacitors mounted in a resonant circuit configuration adjusted to the frequency of the harmonic order to be eliminated. As a passive filter only takes care of one operating point at a time, it is a low cost solution, but is not efficient with partial loads. With the unique disadvantage of low power factor with partial load, a passive filter runs the risk of causing resonances in the network.
An active filter works by measuring the harmonic currents and generating a spectrum of harmonic currents in phase opposition to the measured spectrum. Needs over-sizing to compensate for power factor reduction. An active filter is a good, moderately priced solution to attenuate the harmonics of multiple drives that operate in parallel across a network.
Setting a low harmonic drive consumes power as a normal inverter (converts DC power to AC power). Allows the system to adjust the waveform of the mains current and avoid the impact of harmonics and idle power. Needing more overall space, a low harmonic drive falls in the middle range in terms of cost. Compared to an active filter, the low harmonic drive is simpler and provides more return for the money paid, making it an effective solution.
In summary, the line inductance solution is the best choice for applications where heavier distortions are to be filtered, but harmonic attenuation is not the first priority. The active filter is a good solution to attenuate the harmonics of several parallel drives operating at one point of the coupling. The 12-pulse solution is the most efficient, but also the most complex. For applications where harmonic attenuation is very important, low harmonic drive offers the best solution.
Making the right choice
The best harmonic attenuation solution depends on the nature of the load and the power demand of connected equipment in an industrial environment. The selection factors to consider are:
Compass level or overall space required
Simplicity in operation
Efficiency of harmonic attenuation
Energy Efficiency
Price / performance and value of money
