HOW TO SIZE A CONVERTER

See if you load(s) are listed in our sizing tool for the right converter recommendation 

1. Determine the Total Load (HP or kW)

• Sum of all motor loads: Identify the horsepower (HP) rating or kilowatt (kW) rating of each motor or piece of equipment that will be powered by the converter.
• Running vs. starting loads: Separate the motors into running and starting loads. Motors with high starting loads (such as compressors, pumps, etc.) may require a larger converter. (see sizing chart)

2. Identify Load Types

• Hard-starting loads: Equipment such as air compressors, elevators, or hydraulic pumps requires more power to start than they do to run.
• Light loads: Fans, saws, and similar equipment have lighter startup demands.

3. Determine Motor Start-Up Requirements

• Inrush current (starting current): Motors usually draw 6–8 times the full-load current at startup. High-inrush motors require a larger phase converter to handle the load without tripping or voltage drops.

4. Convert HP to the Correct Rotary Phase Converter Size

• General rule of thumb: A rotary phase converter should typically be sized at 1.5 to 2 times the HP of the largest motor that will be started.
  • Example: For a 10 HP motor, you would need an RPC rated for 15–20 HP.
• Multiple motors: If running multiple motors at once, size the converter based on the largest motor and ensure the total combined HP does not exceed the converter’s rating.

5. Factor in Load Types

• CNC and sensitive electronics: For applications involving CNC machines or sensitive electronics, a balanced rotary phase converter is recommended to maintain consistent voltage across all phases.

6. Consult Manufacturer Guidelines

• Always cross-reference with the manufacturer’s specifications for optimal sizing.

By following these guidelines, you can ensure that your rotary phase converter is appropriately sized for your 3-phase application, avoiding operational issues such as overheating or insufficient power.

Condensed Steps

Determine Total Load: Calculate the total HP or kW of all motors and equipment to be powered.

Identify Load Type: Determine if loads are hard-starting (e.g., compressors) or light-starting (e.g., fans).

Convert HP to Converter Size: Choose an RPC rated 1.5 to 2 times the HP of the largest motor.