What is a Frequency Converter?

A frequency converter is a machine that converts power from one frequency to another frequency.  Either by means of a double conversion Static Frequency Converter or by using a motor  generator set called a Rotary Frequency Converter.  In the double conversion method, the Rectifier converts AC into DC and the Inverter converts DC back into AC.  In an MG set, this is completed by either changing the rotational speed of the generator in the versions with belts & sheaves or the gear box and by means of motors and generators with a different number of poles operating to achieve the same result of producing the desired output frequency.  

Why would I need a Frequency Converter?  

Small components like computers and small electronics operate with what are called switch mode power supplies, that are capable of operating at both 50HZ and 60HZ.  In this case the only item you may need is a plug converter as 50HZ outlets are not the same as 60HZ outlets for the following reason.  As 60Hz and 50Hz operate at different frequency, unless your equipment is operating at 208V (which is used for both 50Hz and 60Hz), you do not want to plug equipment into the wrong power source or you run the risk of damaging equipment and or harming yourself.  Once you let the smoke out of the equipment, you cannot put it back in.  Larger and 3 phase equipment cannot operate on the wrong frequency as this can cause damage or premature wear on the equipment.  The equipment has been designed to operate at 50 Hz and if incorrectly connected to 60 Hz will cause the equipment to operate outside its design criteria, most likely damaging the equipment immediately (remember the smoke) or causing it to fail over time from overheating.  With our ever growing global economy, equipment from other parts of the world are being used more frequently in countries that they were not manufactured in.  This usually results in the need of a Frequency Converter (also called a frequency changer) to change the local utility’s frequency (and sometime its voltage) so it will be compatible with the power requirements of the equipment you are trying to operate (also called the load).

Specific industries have unique frequency requirements and this is based on how they supply power to their equipment.  Aviation and some Weapons systems requires 400Hz, therefore when the equipment is one the group or not operating on the 400HZ being produced on-board, ground power support is needed for the electrical system.

400Hz is also used in many airport and military radar applications. Rail utilize 25, 91.66 or 100Hz to run their signaling systems. Ship yards and docks require frequency conversion of shore power as most ships are built in 50HZ countries, which means the base power systems on the ships will be 50HZ.  In this case you will need a frequency converter to match the electrical needs of ships being built, repaired or docked. There are also many unique and/or variable frequencies needed in laboratories and testing facilities. 

When equipment manufactured in one country and used in another, chances are that you not only have to convert the voltage, but you will also need to convert the frequency.  The most common frequencies are 50Hz and 60Hz, however, there are many applications not related to this issue that effect the need for frequency converters.  Aircraft and weapons systems use 400Hz while rail uses and 100Hz and hydro produces  25Hz .  So WHY are there so many different frequencies?  It is very basic and has to do with the RPM that the prime power producer spins at.  1500 rpm is 50Hz, while 1800 rpm is 60Hz utilizing a 4 pole synchronous generator.  With the globalization of the world’s economies intensifying, the need for frequency conversion is increasing as multinationals from 60Hz countries are doing more business in 50Hz countries and vice-versa.

Rotary Frequency Converter

Rotary Frequency Converter

Static Frequency Converter

Static Frequency Converter

Single Phase Uninterruptible Power Supply

Single Phase Converter

Static Uninterruptible Power Supply Converter

Frequency Converter UPS

Frequency converter technology:

Frequency converters are built in 2 basic forms; Rotary Frequency Converters, manufactured with the use of a Motor Generator and Solid State (Static) Frequency Converters manufactured with the use of semi-conductors and power stages.  The Rotary type is more brute force, while the Static type is designed for non industrial applications.  There are also other topology’s to be considered when deciding on a Frequency Converter.  One factor is if you need the converter to also maintain power output when the utility is no longer available.  In this case, a converter will also be a UPS, called a Frequency Converter UPS.  If the Frequency Converter also needs to clean up a non stable input frequency like accepting a poor frequency range on the input and produce a stable output frequency and voltage, a Dynamic Frequency Regulator should be used.  This unit allows for a very unstable utility, while producing the required output.  

Utilizing experience in the 400Hz industry and from early main-frames, PS&C offers two technologies to solve this power Frequency Converter problem; static (solid state) frequency converters and rotary (Motor-Generator) frequency converters. There are several factors which will help identify which frequency conversion solution is right for your project. PS&C’s technically versed applications group will help you make an assessment of your application and select the best solution for your specific requirement.

Dynamic Frequency Regulator



Dynamic Frequency Regulator



What are some Frequency Converter applications:

  • A factory opens in China with U.S. made manufacturing equipment (50/60Hz Converter).
  • A small airport decides to add helicopter service and repair center (400Hz Converter).
  • American manufacturer purchases machinery from European factory (50/60Hz Converter).
  • A railway decides to increase the amount of track into new territories (100/25Hz Converter).