Subscribe to our weekly newsletters
Subscribe to newsletter


Editor's Note: Danfoss Ltd provide:-

Low harmonic driveLow harmonic drive
Variable speed drive Variable speed drive 
Danfoss drivesDanfoss drives

Request Information

Include Article

Request Information
Terms of use


Request Facilities / Interiors product information

Request Architectural product information External

Request Architectural product information Internal

Request Mechanical HVAC product information

Request Electrical product information


DANFOSS LTD - Harmonic Distortion – An Ever Increasing Problem

The mains voltage supplied by electricity utilities to homes, businesses and industry should be a uniform sinusoidal voltage with a constant amplitude and frequency.

This ideal situation is no longer found in any power grid. This is mainly because consumers take non-sinusoidal current from the grid or have a nonlinear characteristic, e.g. strip lights, light dampers, energy-saving bulbs and frequency converters.

Because of the constantly increasing use of non-linear loads, deviations become increasingly serious.

Irregular power supply influence the performance and operation of electrical equipment, so motors, frequency converters and transformers must be more highly rated to maintain proper operation.

Statutory basis of assessment
The compatibility levels of the standards EN 50160/EN 61000 and, for industrial environments, EN 61000, apply within the scope of the EMC directives.

It is assumed, in principle, that when these levels are observed, all devices and systems fulfil their specified functions without disruption in electrical supply networks.

How feedback occurs
The distortion of the sinusoidal curve shape of the supply network as a result of the intermittent use of electricity by the consumers connected to it is called “network feedback” or “harmonic distortion”.

In the case of variable speed drives, harmonic current distortion is caused by the rectifier part, typically a 6-pulse diode rectifier.

Any periodic function can be described as the sum of a series of sine-wave functions (called a “Fourier transformation”) The figure shows the current drawn by a typical drive with dc coils. Underneath it is deconstructed into pure sinus curves. All but the blue curve represents distortion – unwanted and often harmful currents.

Excessive distortion causes premature aging of electronic equipment. This will, over time, increase the system cost. It will also lower the efficiency, stress – or even destruct - idle compensating systems and overheat components such as the supply transformers and cables.

Reducing feedback
In state-of-the-art frequency converters, harmonic feedback is as standard limited by built-in filter elements such as AC or DC-coils. These are often sufficient to reassure compliance with product and system standards and trouble free operation.

The most common technique is the use of AC-coils in front of or build-in the drive.
Thereby, a significantly lower current distortion can be achieved compared to a basic frequency drive without coils.

DC coils
Built-in DC-chokes dramatically reduces network feedback and ensures the drives comply with the limits of EN 61000-3-12. Although AC and DC-coils have similar harmonic reduction, DC-coil drive has higher efficiency, does no reduction of the voltage to the motor and has a lower fluctuation on the intermediate circuit leading to prolonged life of the product.

Extensive harmonic reduction techniques
In some few cases it can be necessary reduce the harmonic content further, for example in the case of weak networks or emergency power operation. Further mitigation equipment is needed to assure compliance with system standard EN 61000-2-4 or recommendations such as IEEE 519-1992 or G5/4. This can either by done by passive or active means.

Harmonic reduction via passive means is a well known approach, where technologies like multi-pulse drives or passive filters offer a robust and inexpensive mitigation form.

The mitigation performance of passive solutions is unfortunately highly depending on load changes, voltage imbalance and/or voltage pre-distortion.

Passive filtration
Different combinations of coils and capacitors forms different passive filters tuned to the individual drive. They are either tuned for individual harmonic cancellation or for reduction of a range of frequencies.

They offer a practical, -easy add-on, filter for power systems with a large concentration of non-linear loads connected to the same distribution transformer.

Especially at currents lower than 300A, passive harmonic filter offers a cost and performance efficient solution.

Multi-pulse drive
Multi-pulse drives also called transformer solutions are drives where the current is supplied via two or three parallel connected 6-pulse rectifiers over a phase shifting transformer. In theory, the 5th and 7th harmonic currents (for 18-pulse also the 11th and 13th) of the individual phase shifted rectifiers are cancelling out each other. Since some voltage imbalance or harmonic background distortion is always present, a complete cancellation of the 5th and 7th (11th and 13th) is never achieved.

Active harmonic mitigation equipment is still considered a high cost solution. Active mitigation is very effective in reducing harmonic oscillations up to 2 kHz and keeps harmonics disturbance low for the full load range. Consideration must however be given to the effects above 2 kHz, generated by these units themselves. In some cases they make further measures necessary to keep the mains supply clean. Users should ask manufacturers specifically about emission values and counter-measures to secure the operational safety of their plant.

Active Filters
For installation where harmonics troubles are first detected after full installation or a result of continues extensive use of non-linear loads, active filters offers an easy retrofit possibility.

Active filter can be installed in front of several loads and offers a reliable and effective solution. Central harmonic mitigation reassured the highest possible system efficiency and so lowest running expenses.

Low harmonic drives
The most common low harmonic drive is an active front end. Besides the benefits of reducing harmonics AFE’s also offers regenerative braking needed in some applications. The disadvantage of the AFE is it relative low efficiency and the increases du/dt on the controlled motor leading to higher insulation and bearing stress.

The New Danfoss Low Harmonic Drive is a combination of an active filter and a standard AC-drive. It does not offer regenerative braking but is designed with the fewest possible components in the main current path, optimising the energy efficiency and has low output peak voltage and dV/dt, which allows the use of standard IEC60034-17/ 25 motors in most cases.


Kalzip Standing seam roofing Low U-value roofing Metal roofing and cladding Solar solutions Green roof systems News 150210

Pilkington Natural stone tiles Ceramic wall tile Ceramic flooring News 150210

Carlo Gavazzi Inductive sensor Photoelectric sensors Magnetic sensors Power analyser News 150210

Xtralis Fire detection Alarm detection System detection Traffic management News 150210

WYG Consulting engineers Environmental consultants Multi-skilled consultancy Natural environment News 150210

Tileplans Tileplans PVC interlocking floor tiles Laboratory flooring Health and safety floor Automotive laboratory Acoustic Flooring News 150210

Pland Stainless steel sinks Stainless steel bowl Sanitary ware News 150210

Quidos Central air conditioning Air conditioning system AC units News 150210

Stonearth Natural stone products Contemporary natural stone Bamboo bathroom News 150210

Emergi Lite Emergency light Power supply system Architectural feature lighting News 150210

ICS Heat pumps Heat pump installation Carbon reduction commitment News 150210

3M Asbestos safety 3m respirator Respirator mask Asbestos respirator News 160210

WD-40 Home lubricant Motor lubricant Lubricant supplier Lubrication company News 150210

Nudura Insulated concrete forms Zero carbon construction Fastening strips News 150210

Weatherite Air handling unit Air conditioning systems Heat exchangers News 160210

Ardex Epoxy floor Floor screeds Tile adhesives Polyurethane resin News 160210

Flowcrete Floor leveling Resin flooring Floor screeding Resin epoxy News 150210

Crown Wall paint Paint supplies House paint Interior painting News 160210

Twyford Bathrooms design Modern bathroom design Bathroom shower design News 160210

Osram Lighting technologies Lighting solution Efficient light Flourescent lamp News 160210

Tarkett Safety floor Flooring specialist Vinyl floor Safety Tiles News 160210

Sandtoft Roofing tiles Slate roof tiles Clay roof tiles News 170210

Gilberts Air diffusers Linear diffuser Modern diffusers Natural ventilation News 170210

Knauf Wall insulation Knauf insulation Space blanket Wool insulation News 170210

Leaderflush Doors external Doors internal Doorsets Timber doors News 170210

Levolux Solar shading Breeam rating External shading Aerofoil fins News 170210

Schneider Electrical switchgear Electrical distribution design Quality electrical distribution News 170210

Honeywell Motorised valves Safety valves Heating thermostats Honeywell thermostats News 170210

Socomec Data slide rule Power distribution Uninterruptible power supply News 170210

Calibre Imaging products Image processor Audio visual Video electronics News 170210

Nexans Fire resistant cables Safety circuits Electrical power cable News 170210

BSIF Health and Safety Site Safety Safety Equipment Safety Training News 170210

Bentley Software solutions Digital design Smartgeometry conference Digital manufacturing News 170210

Wellers Tax accountants Paye payment Accounting services Accounting firm News 170210

John Brash Timber importer Timber decking Timber roofing Timber cladding News 170210

Danfoss Low harmonic drive Variable speed drive Danfoss drives News 180210

Timberplay Outdoor playground equipment Wood playground equipment Adventure area News 180210

Harlequin Sprung dance floors Dance floor Dance studio floor News 180210

Mumford Timber windows Double glazing Casement windows Window suppliers News 180210

National Floor Show Flooring specialists Flooring exhibition Interior designs Scarlet Opus News 180210

NHBC Professional services Piled foundations Technical advice Assessment services News 180210

Rytons Domestic ventilation systems Extract ventilation system Roof ventilation News 180210

F Ball Installing flooring Install flooring Tiling flooring Wood adhesives News 180210

KBB Exhibition nec birmingham NEC birmingham show KBB exhibition News 180210

Harris Architectural design services Architectural drafting services Commercial architects News 180210

TilePlans Durable flooring Floor covering Showroom floor Flooring tiles News 180210

Twyford Bathrooms design Modern bathroom design Bathroom shower design News 180210

Flowcrete Floor screed Floor leveling Concrete screed Resin flooring News 190210

Knauf Suspended ceiling Ceiling tiles Sound absorption Acoustical ceiling News 190210

Mitsubishi Air curtain Air curtains Heat pumps Air conditioners News 190210

Pilkingtons Ceramic wall tiles Natural stone tiles Marble tiles Porcelain tiles News 190210

MK Electric Power distribution system Electrical accessories Electrical cable management News 190210

CBI Wind power turbines Wind power Wind power projects News 190210

Nittan Fire protection systems Fire protection Fire alarm system News 190210

Panel Systems Wall insulation Insulation products Polystyrene insulation Internal insulation News 190210

John Brash Roofing materials Cladding materials Roofing products Roofing panels News 190210

Gleeds Management consultants Construction consultants Building & construction Building contract News 180210

Roman Shower designer Wet floor shower Wet room drainage News 190210

Carlo Gavazzi Capacitive sensors Inductive sensors Photoelectric sensors Conductive sensor News 190210

McBains Cooper Architectural design services Construction consultants Architectural engineering design News 190210

Monodraught Natural Ventilation SunCatcher Systems SunPipe Systems Sola-powered Systems News 220210

Sandtoft Roof tiles Clay tiles Roof slates Roof tiling News 220210

Dorma Door maintenance Residential doors Doors internal Doors external News 220210

Trend Inverter drives Motor drives Inverter drive Variable speed News 220210

Peabody Commercial property Tenant service authority Social housing regeneration News 220210

Danfoss Variable speed drive Variable speed motors Danfoss drives News 230210

Mitsubishi Air conditioning systems Central air conditioning Air curtain News 230210

Flowcrete Floor leveling Resin flooring Floor screeding Resin epoxy News 230210

Terrys Curtain fabrics Custom curtains Curtain styles Curtain drapery News 230210

Monodraught Natural ventilation Suncatcher systems Sunpipe systems Sola-powered systems News 230210

JS Humidifiers Commercial humidifiers Industrial humidifier Warm humidifiers Home humidifiers News 240210

Pilkington Glass manufacturer Glass supplier Self-cleaning glass Architectural glass News 240210

Raychem Under floor heating Trace heating systems Thermal controls News 240210

Dimplex Heat pumps Solar water heating Renewable energy heating News 240210

Tarkett Sports Flooring Safety floor Flooring specialist Vinyl floor News 240210

Armstrong Ceilings suspended Armstrong ceiling panels Acoustic ceiling panels News 240210

Marshall Management Floor Boxes Underfloor Services Cable Trays Ladders Datatray Cable Trunking Flexible Conduit News 240210

Kawneer Specification guide Architectual aluminium systems Linked sash mechanism News 240210

Chubb Security solutions Security systems Fire & security Data records News 240210

PRP Planning Architectural design Urban design planning Urban landscape design News 240210

Bilco Roof hatches Smoke vent Fire ventilation Access doors News 240210

Hydro-International Rainwater Harvesting Sustainable drainage Storm water control system News 240210

John Laing Investment companies UK development Green gyms Regeneration projects News 240210

Intelli Heat Electric heaters Electric radiators Panel heaters Heat electric News 250210

AET Under floor air conditioning Flexible space Floor raised News 250210

Osram Light sensor Sustainable lighting Efficient lights Lighting technologies News 250210

Schueco Part L Super-insulated facade Photovaltaic panels Curtain wall News 250210

Harlequin Sprung dance floors Dance floor Dance studio floor News 250210

Cembrit Roof slates Cement slates Roof slate Natural slate News 250210

BCL Specialist construction Civil engineers Safety applications Industrial maintenance News 250210

Semieta Software system Access data Software specialists IT data News 250210

Flowcrete Floor screeds Concrete screed Resin flooring Floor leveling News 260210

Pilkington Glass manufacturer Glass supplier Self-cleaning glass Architectural glass News 260210

Danfoss Low harmonic drive Variable speed drive Danfoss drives News 260210

Sandtoft Roof tiles Slate roofing Roofing systems Clay tile News 260210

Andrews Water heater Electric water heaters Gas water heaters News 260210

Potterton Commercial boilers Boilers water heaters Commercial water boilers News 260210

Besam Sliding doors Folding doors Automatic door Swing door News 260210

CIOB Facilities management Building facilities management Architecture and surveying News 26.02.10

Timoleon Under floor insulation Heating company Floor heating systems News 260210

Lindab Rainwater recovery system Drainage design Rainwater drainage systems News 260210

Wienerberger Brick manufacturer Clay brick manufacturers Heavy building materials News 26021

BSIF Health and Safety Site Safety Safety Equipment Safety Training News 260210

Arundel Jones Associates Ltd Registered in England and Wales No. 07334149
Hill Farm, Linton Hill, Maidstone, Kent ME 17 4AL
Tel : 01622 745333 email
copyright all rights reserved

News Categories : Low harmonic drive
Variable speed drive
Danfoss drives