Most HVAC applications involving single phase fans don’t need a three phase drive. They need a straightforward single phase in, single phase out VSD that takes a BMS signal and adjusts motor speed accordingly. That’s what Powerform’s RC10x series does.
Before you specify one, there are a few things worth getting right.
The control signal
Powerform VSDs accept either a 0-10V DC or 2-20mA control signal. Which one you use depends on what your BMS outputs. Both are supported across the range with no additional hardware. There’s also an internal 10V DC source on the larger models, useful if the BMS controller needs a reference voltage. At signal levels below 1V DC or 2mA, the unit shuts off automatically. The fan stops cleanly rather than hunting at the bottom of the speed range.
Motor compatibility
The RC10x series suits PSC motors, the most common type in single phase HVAC fans, as well as shaded pole and universal motors. If the load torque varies with speed these drives handle it well. Fixed torque loads are a different conversation. Check the motor nameplate current and add a margin. Powerform publishes continuous RMS ratings with no de-rating, so the 10A model (RC110D) is rated to 10A continuous, not 10A peak.
The minimum speed adjuster
This is the setting that gets skipped most often and causes the most problems later.
PSC motors need airflow across the rotor to cool themselves. Run the fan too slowly and the motor draws current without moving enough air. It overheats. At best you get nuisance thermal trips; at worst the motor fails early. The minimum speed adjuster sets a floor. Whatever signal comes from the BMS, the fan won’t run below this point. Set it during commissioning with a clamp meter on the motor to find the speed where the current starts to rise without a corresponding airflow increase, set the minimum just above it. Five minutes during commissioning can save a warranty call six months later.
The maximum speed adjuster
Less critical but useful for air balancing. If the design airflow requires the fan at 80% speed, set the maximum adjuster so a 10V signal from the BMS gives you that flow. The BMS operates across its full 0-10V range, the fan operates within its designed limits. Useful on retrofit projects where the fan is oversized for the original duct layout.
Sizing
Models run from 2.5A (RC103, 600VA) up to 20A (RC120D, 4800VA). For a single fan, pick the next model up from the motor nameplate current. For multiple fans on one drive add the nameplate currents and apply the same logic.
BMS integration
All models are BMS compatible. Control signals are isolated from mains via optocouplers. EMI filters are integral to the unit.
If you’ve got a project with single phase fans that need speed control and BMS integration, call us. We’ve been making these in Australia for over 50 years and can help work out the right model.
https://powerform.com.au/product-category/variable-speed-drives/
02 9460 8881