What is a Static Frequency Converter?

A static frequency converter, also called a solid state frequency converter, is an electronic device that converts the frequency of an incoming power supply to a different desired output frequency.

It has the name static frequency converter because it has no moving parts throughout its entire power path – excluding any auxiliary moving parts, such as fans for cooling.

Its purpose is to feed loads that require a different frequency from that supplied by the grid by using an intermediate DC transformation.

What is a Rotary Frequency Converter?

A rotary frequency converter is a device that converts the frequency of an incoming power supply to a different desired output frequency. The frequency is converted using a rotary machine, typically an electric motor and generator, hence its name.

The input AC power is used to spin the motor which then transmits its power to the generator. This then converts the mechanical power into the required AC output power.

Rotary frequency converters are often used in industrial and aerospace applications where high-power capacity and a wide range of output frequencies are required.

Rotary Frequency ConverterStatic Frequency Converter
Less costly per kW at > 5 KVALess costly per kW at 1-3 KVA
Costing isn’t linear with power, e.g. 3 x power costs 1.5 x moreCosts are generally more linear, e.g. 3 x power costs 3 x more
Most suitable for larger applications, i.e. > 10 KVAMost suitable for smaller applications, i.e. < 5 KVA
Fixed output frequencyVariable output frequency
Regular maintenance is requiredLittle to no maintenance is required
Audible noiseLittle to no noise
Full load efficiency 60 to 65% on smallest units and up to 85 to 92% on large unitsFull load efficiency of 60 to 92 % for all sizes
Efficiency varies with load, better with heavy loadsEfficiency varies with load, better with heavy resistive loads and lower output frequencies

What are the Benefits of a Static Frequency Converter?

Static frequency converters are smaller, lighter and almost always more affordable than their rotary counterparts. This means they take up less space and reduces the need for reinforcement of floors that is often required for rotary frequency converters.

When using a static system you have the ability to add smaller increments on redundancy, i.e. using 50kVA modules rather than having to use a whole 800kVA system.

Overall, static frequency converters required far less maintenance than rotary alternatives. This is because solid-state converters have no moving parts, meaning there’s much less to go wrong! This also means that you’ll benefit from a reduction in downtime for repairs too.

Static frequency converters are ‘always on’, meaning there are no delays when you need to power your machinery. Plus, their outputs are incredibly precise in terms of voltage and frequency, as well as very high accuracy on output sinewaves, which is ideal for applications that require exact or ‘clean’ power.

Another benefit to static frequency converters is that they also give you the ability to monitor them remotely. They also have higher power factors with lower losses, which works to reduce running costs rather significantly!

Additionally, static frequency converters are far quieter than their rotary counterparts thanks to the lack of moving parts – something to bear in mind when choosing between frequency converter types.

What are the Benefits of a Rotary Frequency Converter?

One of the benefits of a rotary frequency converter is that they have an arguably longer asset lifetime compared to their static counterparts – although it’s worth bearing in mind that thanks to their moving parts, they require more frequent maintenance to prolong their life.

In terms of their operation, rotary frequency converters provide unique advantages over the static kind. They produce a pure sinewave, which is a steady and continuous wave that provides a smooth oscillation; something that a lot of machinery requires to function correctly.

They are also far better at handling in-rush current, thereby protecting your machinery from surges. Plus, they have a better ability to hand a ‘dirty’ supply, typical of the supply found in more exotic territories, and convert it into a clean output that’s safe to use.