Harmonic Filter

Harmonic Filter prevents electronic & electrical failure & drive tripping on grid voltage fluctuation. Slash equipment footprint, energy & maintenance cost. Worldwide all power intensive projects are designed with only-one choice passive harmonic filter which when super tuned delivers considerable achievements on the factory's productivity and profitability that any of our 350+ repeat corporate clients will tell you.

Super Tuned Harmonic Filter performance - on Failure & Tripping, Product-Quality & Electrical-Blast.

Failure & Tripping: PHF draws-out current harmonics from downstream loads, mitigate it from harmonic overload, reduce voltage-harmonics build-up which otherwise in a chain-reaction increase additional current harmonics. In a harmonic-rich environment with high THDv and THDi, it eliminates drive tripping on over-current - you may read the case study at increase-productivity-through-harmonic-solution. The super tuned harmonic filters not only remove both THDv and THDi much below IEEE-519 limits - but work for the benefit of your machinery's extended life, plant's productivity and corporate profitability. It eliminates 80 to 90% failures involving DC and VFD drive, electronic card and electrical equipment. With its large LC circuit and reconstruction of the distorted sinusoidal waveform, it gets rid of 80 to 90% nuisance tripping due to grid voltage fluctuation involving a drive, electronic-gadget, switch-gear or protective relay. 

Produce Quality: PHF removes dirty power, power surge and most of the momentary voltage sag from a transformer's electrical power system and supplies clean and quality power to all machinery like drives, industrial electronics, data centre servers, switchgear, and electrical equipment. It attenuates the machinery from over-weight harmonic distortion and improves it into a lively performance devoid of a reasonable shake or sway. Product quality improves significantly for any sensitive-manufacturing process. We have tracked several post harmonic filter installations for a year long and observed the end-product quality rejection has improved by 50% on a six sigma scale - that brings back 50% waste to corporate wealth. 

Electrical Blasting: A mandate is increasingly becoming noticeable among electrical engineers and safety regulators is to dress in a space suit a la arc flash suit. We are using non-linear-loads since the 1970s, but the Arc Flash issue came into prominence since 2005. What could be the reason? We are increasingly using variable frequency drives since then. Today VFD drives almost every other induction motor rightfully or otherwise. The switching frequency also called carrier frequency of a VFD drive is the rate at which it's DC bus voltage is switched on and off during pulse width modulation (PWM) process. VFD manufacturers increase switching frequency apparently to reduce audible noise from the motor and harmonic generation. VFD typically operate in a 4-20khz range. At a higher switching frequency, the noise pitch from stator lamination moves higher beyond human hearing range - so we hear a lower audible noise from the motor. Similarly, at a higher switching frequency, the measurable harmonic generation typically up to 50th order are lesser which matters for the sake of regulation and beyond it is passed on to the kilo Hz range harmonics. The kHz range harmonics under a favourable power system condition create a common mode voltage (CMV) and occupy a place within an electrical power system. It could be a switchgear panel - and the incidents that we troubleshoot always turned out to be an electrical panel. The final resolution of the built-up CMV is to discharge. In the absence of a calibrated mechanism, it takes the violent discharge path that resuls in an electrical blast. We use a zero sequence winding with our harmonic filter and solidly connect that to the ground establishing the discharge path. We have written a separate case study for electrical arc flash  - you may read the case study at Mitigate VFD Harmonics.

Front End Harmonic Filter - Drive wise harmonic correction

Drive wise harmonic filtering is called frontend type. When a transformer has a few small size VFD Drives it can be applied. We use a zig-zag winding for the series reactor which ensures minimum voltage drop and prevents harmonic overloading into the main parallel harmonic filter.

In case of a transformer having few higher rating VFD Drives, we apply only parallel harmonic filters across each VFD. If the transformer has too many VFD Drives, our recommendation is to use a single harmonic filter at the transformer incomer bus.

The advantages of using a single harmonic filter for the full transformer loads are substantial. Accurate and calibrated control of power, harmonics and power factor from minimum to full working load of the transformer. A passive harmonic filter can take out harmonics from all downstream VFD Drives. A transformer end single harmonic filter will have larger LC-circuit which is a better device to control power surge and sudden voltage fluctuations than smaller sized drive wise harmonic filters.

If the application demands, we even use a small parallel filter. As in Fig.1, we have used a 10A harmonic filter in parallel with a VFD Drive for a 30TR package air-conditioner in a corporate building. The AC unit was facing VFD card failure problem.

 The industry standard for drive wise harmonic control is different though. Our peers use large series reactors in multiples. Some OEM provides variable tapping. They may not cause much harm when the transformer employs a few small size VFD Drives, even though a no-harmonic solution is a better option.

But when the transformer supplies to large sized VFDs, the series reactors cause a significant voltage drop that magnifies THDv and disturbs VFD operation. The VFD Drives become too susceptible to voltage fluctuation and even a minor voltage sag trips the VFD. 

Harmonic Filter Specifications: Designing Tuned Harmonic Filter, auto-variable or fixed type, requires Power System modelling and load specific data. The required Engineering efforts are much needed for effectively Improving the electrical Power Quality by Mitigating Harmonic Distortions, both Total Voltage Harmonic Distortions (THDv) and Total Current Harmonics Distortion (THDi). Tuned Harmonic Filter Design requires tuning with the Plants Power System impedance and this solution is not a mass manufacturing process but a service manufacturing, and a knowledge based custom engineering product for the manufacturers of harmonic filters. It slashes Energy Bill (kWh Energy Conservation) by up to 15% and Demand Cost (kVAh Savings) by up to 50%. those depending upon the load characteristics and harmonic distortions in the power system. The variable tuned harmonic filter maintains unity Power Factor PF, and adjusts with the load demand ... ... ...

The Full Case Study: please read it at #HarmonicFilter.