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3 Phase Filters for Single Phase Applications

Guidance on how to use 3 phase EMC filters in higher current single phase applications.

Three phase power supplies have many advantages over single phase especially in higher power industrial applications. They allow more power to be transmitted whilst using smaller conductors. Single phase on the other hand is much simpler and is found in low power applications such as in our homes.

In general this distinction seems to kick in around 20- 50A single phase. Above 20A single phase people start to use 3 phase instead. For us filter manufacturers the number of applications seen for single phase filters tails off above 20A and becomes very rare at 50A or above. This means that we do not develop new products for high current single phase filters so when one is needed it can be harder to find.

However there is a solution: standard 3 phase filters can be used in single phase applications. If, for example, you have a 100A single phase application you can source a 100A 3 phase filter. At this point it is important to point out that all Roxburgh EMC 3 phase filter current ratings are specified per phase. Therefore a 100A 3 phase filter can carry 100A per phase. You can connect your 3 phase filter to your single phase supply. Take care to connect the same phase line and load side so if your live is connected to L1 line side it should also be connected to L1 load side. The same should be done with the neutral, this should be connected to another live but the same one line and load side.

It’s important to understand that any ‘unused’ filter terminals will contain hazardous voltages induced upon them. Therefore, a warning label and extra insulation such as an insulated terminal boot or terminal cover should be used to avoid accidental contact or maintain IP ratings.

The 3 phase filter connected in this way to a single phase supply will work just as well as it would have if connected to a 3 phase supply.

In addition to use in single phase applications 3 phase filters can also be used in phase to phase or 2 phase applications. These installations are relatively rare though still seen in some specialist applications such has high power heating elements or welding. Phase to phase power can also be thought of as a 400V single phase supply. Most single phase filters have a maximum voltage rating of 250V so cannot be used but 3 phase filters typically have a 500V rating so can again be deployed with one terminal unused but insulated.

To see 3 phase filters which could be used in high current single phase applications please see the following links:
Three Phase Industrial Mains Filter - KMFA
Three Phase Industrial Multi Stage Drive Filter - MIF3

For additional information call our technical team on 01724 273228.


See Download Below: Wiring diagram for 3 phase filters used in single phase applications.

Article first published : 30|1|2020