Electric arc welding device

Power Metering

Industrial and domestic kWh meters


Lifts, escalators and autowalks

AC drives

Motor speed control


Ininterruptable  Power Suply

Switching Power Supplies

Switched Mode Power Supplies and DC-DC Converters

Core competences in inductive Components and EMC Filters

Inductive components in industrial applications

Among the wide range of applications in industrial technology, various ones are defined as PRAX market competence.


PRAX develops and produces inductive components and EMC filters for electric arc welding devices, plastic welding devices and stud welding devices.

Inverters and power supplies for welding equipment are in the power range from 1kW up to 20kWand are based on a high output current, which is generating the soldering heat.

The power supply is based on switching topologies, usually using full bridge techniques. As weight and efficiency is a key point for such equipment, the most extended circuit is full bridge with zero voltage switching (ZVS). Such technique allowsreducing switching losses, therefore increasingswitching frequency (reducing size and improving efficiency) or use IGBTs instead of mosfets for further cost reduction possibilities.

PRAX designs and manufactures transformers and output chokes for switching converters and inverters. With our know-how of the most advanced resonant switching topologies we are able to propose optimal designs according to customer needs and expectations.

Safety regulation is a must for welding equipments, which are usually connected to a high voltage circuit. The main transformer is one of the key components helping to reach such regulation. PRAX components are designed to meet EN 61558 safety standard for inductors and transformers. We manufacture also according to UL Electrical Insulation System (class F and class H).

Among main transformer and output choke, PRAX is also expert in designing and manufacturing filtering inductors, gate drive transformers, current sensors and flyback transformers for the power supply control unit.

Power metering

Power metering devices, so called Watt-Hour meters, measure power line consuming. In order to make an accurate measurement and, at the end, count exactly how many Watts are used, it is very important to know the exact value of the consumed current.

There are several methods to measure such current, but the most extended one is by using a current sensor, which provides high accuracy among galvanic isolation.

PRAX experience and know-how of this application allows designing and manufacturinghigh precision current sensors from 6 Amps up to 120 Amps. The component design minimizes amplitude and phase error, achieving almost cos(Ф) = 1. With this accuracy levels, current sensors manufactured by PRAX can be applied up to class 0.1 watt-hour meters.

Concerning technology, PRAX uses world-class magnetic material:

  • Nanocristaline: High permeability toroid to achieve the highest accuracy.
  • Amorphous Co based: High permeability and DC immunity to archive high accuracy while meeting IEC 1036 standard.


PRAX offers EMC filters specially designed for lifting equipment and variable-speed devices, such as elevators or escalators.

Elevation systems work with variable speed, acceleration and braking, with motors controlled by AC drives. Such drives work in switch-mode generating EMI, which must be attenuated with an EMC filter to assure disturbances below the maximum allowed by the applied directive. PRAX applies European Directive EN12015:2005 for EMC tests in elevators.

In elevation systems, AC Drives and motor are eventually not close to each other so long cables must be used for connection. In this case, high dV/dt peak voltages appear with associated risk of premature damage of motorwindings. To avoid such an effect, PRAX offers dV/dt filters to keep itbelow 500 V/us.

AC Drives

PRAX can offer specially designed EMC Filters for AC drives for the most common and known brands (Omron, Yaskawa, Fuji, LG, Control Techniques, Emerson, Panasonic, Mitsubishi, ABB).

With two stages topology, these EMC filters have a very high attenuation from 150 kHz to 30 MHz and have been especially designed and optimized to meet specific product standard EN61800-3:2004 requirements for drives systems.

Foot print shape is available in order to improve performance for AC drives, as well as different types of connections (terminal block, cables, screws, bus bars, etc…).


Uninterruptable Power Supplies are devices that convert DC voltage from a battery panel to an AC voltage to deliver power to the grid. It’s widely used in industrial electronics to assure power availability in the grid when the mains net fall down. Similar to renewable energies, UPS use a switching inverter to convert DC voltage into an AC voltage.

Power ratings vary from small devices of 1kW to more than 1MW. In UPS inverters, unlike those for renewable energies, cost is the main driver instead of efficiency. Furthermore, they are allowed to produce higher harmonic distortion since they are not delivering power to the main grid. So, inductance values for input and output filtering chokes are in the range of hundreds of micro-henries. Inrenewable energies inverters these inductance values are commonly ten times higher.

PRAX is able to design and produce optimized cost effective solutions for input and output inductors in the power range from 1kW up to 300kW. In order to optimize cost and assuring a good efficiency the best magnetic material is gapped ferrite (while sendust, iron powder or amorphous can be used either). Ferrite material-based chokes can be either easily stacked in a multi-E choke, or in series and parallel conforming a power tower inductor. An UPS works in switch-mode and generates electromagnetic noise, conducted and radiated, which affects operation into the nearby electronic devices.This electromagnetic emission must meet established limits by applicable standards. Working environment must also be considered. Typical standard isEN 62040-2:2006.

One of the EMC tests to perform is for conducted emissions. In such a test, noise in the load is measured by using a LISN. Measurement frequency range 150 kHz - 30 MHz and the maximum permitted limit depends on the applicable standard and the environment where they are going to work, domestic or industrial.

To overcome these conducted emission tests, PRAX offers a wide range of EMC filters for UPS, with various ranges of current, voltage and filter stages, designed and built according to UL1283 and EN60939-2 standards. PRAX offers three-phase plus neutral filters, specially designed transformerless UPS.

Among energy storage chokes and EMC filters, PRAX is also expert in designing and manufacturing Common Mode chokes, gate drive transformers, current sensors and flyback transformers for the power supply control unit.

Switched Mode Power Supplies

Most of industrial electronics applications, to power the devices, use switch-mode power supplies. Power range goes from small power supplies of 5W to big racks of 20kW. Switching technologies are widely used in the market, and differs from linear technologies in the increase of efficiency reducing converter size.

Usually depending on the power rating, different circuit topologies are applied in the power supply. Commonly used topologies are flyback, forward, push-pull, half-bridge and full-bridge.With the aim of improving efficiency new topologies have been lately introduced, like ZVT, phase-shifted or Half-Bridge LLC.

Power transformer is one of the key components of the power supply, and its function is to provide energy to the load and to assure isolation between high and low voltage circuits.

PRAX experience in standard and complex topologies allows design and manufacturingof optimized inductive components in almost any format and material. Benefits are size and cost reduction, with efficiency maximization.

Main transformer is considered a safety component; PRAX is also expert in designing according to the safety standard regulation applied to a concrete sector (EN-60950 for telecommunication systems, EN-60601 for medical systems, EN-61558 for welding equipment), assuring creepage and clearance distances compliancy, among insulation requirements.

While power transformer is the most important inductive component in a switch mode power supply, PRAX is also expert in filtering inductors, current transformers, output chokes and gate drive transformers.

PRAX also offers EMC filters for switched mode power supplies with a very high differential attenuation. Differential mode noise is specially high in SMPS, so one of the two stages in these filters has specific differential chokes and Cx capacitors. Common mode noise is also attenuated with common mode chokes and Cy capacitors.

Such filters perform their best from 150 kHz to 30 MHz in order to achieve maximum emission limits defined by the applied standard. PRAX EMC filters are available for different currents, phases, voltages, shapes, housing materials, housing connections, electrical connections (fast-on, cable, screws, cables, IEC connectors, with fuses, etc…) in order to achieve customer requirements.