Rotary Phase Converter Power Consumption

If you are like many shop owners, you are probably wondering if connecting a Rotary Phase Converter along with your equipment will trip a circuit breaker or not? Knowing your RPC power consumption will also allow you to calculate the right breaker size.

In a Rotary Phase Converter, two single-phase lines are distributed among three output lines. The square root of 3 (1.732) is used for figuring out how much power is required to be produced by a Rotary Phase Converter in order to run your equipment.

If your motor size is 5 HP and it draws 15 amps (as stated on the nameplate), you will need to:

Multiply 15 x 1.732 = to get 25.98 amps

This means if you add your Rotary Phase converter’s amperage (which should also be written on the motor data plate) to this number, you will get a complete picture of the amperage required to run your converter under load.

When you’ll figure out how much output your Rotary Phase Converter needs to produce to accommodate your needs, selecting the right phase converter for you should be a much simpler task.

So, how much amperage does your Rotary Phase Converter draw? A typical idling 10 HP converter will draw around 3.5 to 10 amps and the best way to figure out how much it really draws is to take the ampere reading of the power that is coming in while it’s working.

If you add a load to it, your converter will draw additional amps depending on the size and usage of your motor. The formula for calculating amp usage under load goes as follows:

Load motor amps x 1.732 + idle motor amps

As an example, if you have an idling motor generator that draws 10 amps and a 5 HP motor that draws 15 amps, we multiply 15 by 1.732 (=25.98) and add them up (10 + 25.98 = 35.98). In this scenario, your amp usage will be about 36 amps.

This means that the third leg that the converter generates will increase the current draw by 1.732. If your motors are NOT used at their maximum capacity, then it will draw less.

How much current it draws typically depends on where the run capacitors are placed and the amount of them (power factor). It also makes a difference in how the wiring is done.

It is also important to know that a properly balanced phase converter will not only run your equipment smoothly but will also decrease overall power consumption. You can accomplish this by adding a bunch of Run capacitors to your converter setup or consider getting a brand new quality Rotary Phase Converter.

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