Inverters are the backbone of modern industry, energy transition and infrastructure. Whether precisely controlling a production line, feeding back solar energy or powering a metro: without inverters, everything comes to a standstill. An inverter is an electrical device that converts the properties of electrical energy - such as voltage, current shape or frequency - to make it suitable for a specific application.
Yet the massive deployment of these power electronics brings a downside. Due to their switching operation, inverters are one of the biggest sources of Power Quality problems, such as harmonic contamination and supraharmonics. This article provides an in-depth overview of the different types of inverters (AC, DC, AFE), their specific applications in the industrial and marine sectors, and the technical measures needed to ensure the operational reliability of your installation.
Short on time? Here are the key points you need to know:
Function: Inverters convert electrical energy (AC/DC, level, frequency) for specific loads such as motors and LED lighting.
Classification: We distinguish four main groups: Rectifiers (AC-DC), Inverters (DC-AC), Frequency Converters (AC-AC) and DC-DC converters.
Risk: The non-linear current draw of inverters causes harmonics and voltage distortion, leading to failures and additional heat generation.
Point of note: Active Front End (AFE) technology reduces classical harmonics, but often introduces supraharmonics (2-150 kHz).
Advice: Always combine inverters with an appropriate Power Quality design (filtering and monitoring) to prevent outages.
Inverters are ubiquitous in environments where precision, efficiency and control are required. In the domestic sphere, we know them from solar panels and EV chargers, but the greatest challenges and capabilities lie in the professional sector.
Relevant sectors and applications:
For Technical Managers and Installation Managers in these sectors, inverter knowledge is crucial. After all, a faltering inverter often means immediate downtime of a primary process.
Inverters are generally classified according to their inputs and outputs. We distinguish four main categories, each playing a specific role in the energy chain.
1. AC to DC inverters (Rectifiers)
This type, also known as rectifier , converts alternating current (AC) from the grid to direct current (DC). This is often the first step in powering electronics or the DC link of an AC drive.
2. DC to AC inverters (Inverters)
The inverter does the opposite: it turns direct current into alternating current. This is essential for feeding energy from batteries or solar panels back into the AC grid, or for driving AC motors from a DC intermediate circuit. Here, the output frequency and voltage can often be set variably.
3. DC to DC inverters (Choppers / Isolation Inverters)
These inverters, often referred to as choppers or DC-DC converters, increase (boost) or decrease (buck) a DC voltage level. In industry, they often act as isolation converters. They provide galvanic isolation and voltage stabilisation in critical systems such as subways, ship lifts and control circuits of high-voltage systems.
4. AC to AC inverters (Frequency inverters)
This is the most complex and common group in drive engineering. Its purpose is to adjust the frequency (and often the voltage) of the power supply to control the rotational speed of electric motors.
Within AC-AC inverters, we see different technologies, each with its own impact on Power Quality.
From Cycloconverter to AC-DC-AC: Older technologies such as the Cycloconverter (direct conversion without an intermediate circuit) are still used at huge power levels in shipping and heavy industry. However, they are complex and generate a lot of reactive power. The Matrix Converter offers a lot of flexibility by being able to connect any input phase directly to any output phase, but is less widespread in practice than the AC-DC-AC converter.
In AC-DC-AC topology, the alternating voltage is first rectified (AC-DC), smoothed in a capacitor bank (DC bus) and then converted back to alternating voltage (DC-AC). This provides maximum control over motor behaviour.
Active Front End (AFE): The solution and the new problem Traditional AC-DC-AC inverters use diodes at the input, leading to high harmonic currents (especially the 5th and 7th harmonics). An Active Front End (AFE) replaces these diodes with switching IGBTs.
Although inverters are essential for process optimisation, they behave as a non-linear load. Unlike a light bulb or heating element, an inverter does not draw current evenly, but in short pulses.
This results in three main issues:
Consequence in practice: An installation with many inverters without adequate filtering may experience unexplained control system failures, flickering lighting, or even tripping of protection devices at loads well below rated power.
Completely removing inverters is not an option; controlling their behaviour is. There are several methods to ensure Power Quality in an environment with many power electronics.
Are you experiencing problems in an installation with many inverters? Run through these steps:
Selecting and installing a standard inverter is everyday work for the E-installer. However, as soon as power electronics are a dominant part of your installation, or when operational reliability leaves no room for compromise, specialist knowledge is required.
Why HyTEPS? We do not believe in 'one-size-fits-all'. Whether the solution lies in an Active Harmonic Filter, a specific transformer configuration or adjusting the cable route: our advice is always based on measurement data and electrical engineering laws of nature, not sales targets.
Delve further into the subject matter via these related pages:
Symptoms are often subtle until things go wrong. Look out for unexplained machine failures, flickering lights, cables getting hot or transformers buzzing. Also, if electronics (PLCs, drivers) fail earlier than the service life indicates, chances are that the power quality is insufficient. A Power Quality measurement provides the answer.
This is possible, provided you have a high-quality Power Quality Analyzer (according to IEC 61000-4-30 Class A) and the knowledge to interpret the data. Collecting data is easy; analysing the correlation between events, harmonics and your specific business processes requires specialist engineering knowledge. We are happy to support you in the analysis.
Not by definition. NEN-EN 50160 describes the minimum requirements for voltage at the grid operator's transfer point. However, modern equipment can be more sensitive and malfunction even if the voltage is within this standard. We therefore look beyond the standard: we look at the compatibility between your power supply and your connected load.
Peace of mind, certainty and insight. You get a clear diagnosis of the 'health' of your electrical installation. We pinpoint the cause of faults, enabling you to avoid unplanned downtime and reduce fire risks or unnecessary energy losses. You receive a concrete advisory report with practical points for improvement.
No, that is a misconception. A filter is a powerful tool, but not a panacea. Sometimes the solution lies in changing transformer settings, redistributing loads or adjusting cabling. HyTEPS always recommends a thorough analysis and simulation before we recommend hardware, to avoid unnecessary investments.
Yes, significantly. Solar panel inverters and LED lighting drivers are non-linear loads that cause harmonics and sometimes supraharmonics. This can lead to interference with other equipment or overloading of the neutral conductor. When renovating or preserving, a Power Quality check is essential to ensure operational reliability.
We call this phenomenon 'nuisance tripping'. Often the cause is not the total amount of current, but the distortion of the current (harmonics) or short peak currents that your measuring equipment misses. This contamination can extra heat up thermal protections or confuse electronic protections, causing them to switch off wrongly. A specialised measurement can find out exactly why a protection reacts.
For a reliable picture, we usually measure at least one to two weeks. This is necessary to capture a full duty cycle, including weekends and peak loads. For specific acute failures, we can also take short-term measurements or deploy 'continuous waveform recording' to capture transients.
Your installer is an expert in installation and maintenance (the 'general practitioner'). HyTEPS is the specialist (the 'Power Quality Doctor'). We have advanced measuring equipment, simulation software and in-depth knowledge of theoretical electrical engineering and regulations. We often work together with installers to solve complex puzzles that fall outside standard knowledge.
After the measurement, you receive a report with conclusions in understandable language as well as technical details. If necessary, we simulate the possible solutions in our software. So you know exactly what the effect of a measure will be in advance. We then supervise the implementation and verify the result with a follow-up measurement.
Inverters are indispensable, but require a proactive approach in terms of Power Quality. Want to be sure that your inverters, PV inverters or DC converters are functioning optimally and safely?
HyTEPS
Beemdstraat 3
5653 MA Eindhoven
