Harmonics

Insights into drives technology

Harmonics cause interruptions, interference, and downtime by polluting the electrical network and making connected equipment behave erratically.

Harmonics can cause damage to sensitive electronics, interference in communication equipment, and false readings on measurement devices. Harmonics can trip circuit breakers, blow fuses and cause capacitor failures. The effects also include overheating of transformers, cables, motors, generators and capacitors. Equipment must be designed to tolerate harmonics in the network, and oversizing leads to higher investment costs and underutilized capacity.

The problems caused by harmonics result in increased losses because more energy is wasted due to overheating, equipment has a shorter life time and is subject to unreliable operation. In the worst cases, harmonics cause unnecessary and unwanted process interruptions.

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What are harmonics

In an ideal case, the current in an electrical grid is a pure sine wave and does not contain harmonics. In reality the current deviates from this pure sine wave and contains harmonics. A pure sinusoidal voltage and current does not contain any harmonics Voltage and current that deviate from the sine form contain harmonics The total amount of harmonics is expressed as a THD% value (= total harmonic distortion).

	A pure sinusoidal voltage and current does not contain any harmonics
	Voltage and current that deviate from the sine form contain harmonics

What causes harmonics

Harmonics are introduced into the electrical network by non-linear loads, such as

power supplies of PCs, PLCs, TVs etc.
photocopiers, domestic appliances
diode and thyristor bridges
uninterruptible power supplies
motor starters
switched-mode power supplies
variable speed drives

Ultra-low harmonic drives by ABB

Prevention is better than a cure for the symptoms

keep the electrical network clean
reduce the risk of disturbances
prevent damage to other equipment
prevent interference with communications equipment
reduce the installation footprint
reduce the total cost of ownership

Instead of trying to tackle harmonics by often ineffective actions, like adding cooling or over-dimensioning equipment, why not employ equipment that do not cause harmonics in the first place?

Low harmonic content

Our ultra-low harmonic drive produces exceptionally low harmonic content and exceeds requirements set by low harmonic standards. Compared to a conventional drive, the harmonic content is reduced by up to 97%. The total harmonic current distortion is typically 3%. With a passive filter the typical total harmonic distortion is between 5 to 10%.

Harmonic content reduction up to	Harmonic distortion typically

Simple and cost-efficient installation

The compact drive features built-in harmonics mitigation. This includes an active supply unit and a low harmonic line filter. As there is no need for external filters, multi-pulse arrangements or special transformers, the simple installation offers significant space, time and cost savings.

As there is less risk of overheating with lower harmonic currents, there is no need to over-dimension equipment such as transformers and cables.

Output voltage stabilization - secured operation and optimized dimensioning

The drive’s active supply unit can boost the output voltage to enable full motor voltage, even when the supply voltage is below nominal. This ensures reliable operation in weak networks.

This voltage boost capability can also be utilized to overcome voltage drops caused by long supply or motor cables. Therefore there is no need to over-dimension the motor or supply transformer due to long cables.

The possibility to stabilize the output voltage of an ultra-low harmonic drive is an advantage compared to passive filter solutions. At nominal loads with a passive filter there is typically a 5% voltage drop. On partial loads on the other hand the voltage over the passive filter can rise by up to 10%, creating the possibility of an overvoltage fault occurring.

Efficient energy utilization

Ultra-low harmonic drives achieve a unity power factor, indicating that electrical energy is being used efficiently.

The drive offers the possibility for network power factor correction in order to compensate for the low power factors of equipment connected to the same network. It can help to avoid penalty charges set by electrical utilities for poor power factors.

Lower harmonics and full motor voltage at all times mean reduced system losses and better overall system efficiency.

For all industries and applications

Our ACS880 ultra-low harmonic drives are customized to meet the precise needs of most industries, such as the oil and gas, chemical, pulp and paper, food and beverage, rubber and plastics, marine, metals and mining industries.

Industry specific ultra-low harmonic drives ACH580 and ACQ580 are available for the HVAC and water industries.