Variable Frequency Drive (VFD/VSD) — Single Phase 240V Input
What Does a Variable Frequency Drive (VFD) Actually Do?
A Variable Frequency Drive — also called a VSD (Variable Speed Drive) or inverter drive — takes your standard single-phase 240 V household supply and outputs a synthetic three-phase signal to run a three-phase motor. Inside the unit, a rectifier converts AC to DC, a capacitor bank smooths the DC bus (reaching approximately 340 V DC from a 240 V input), and an IGBT inverter switches that DC back into a variable three-phase AC waveform. The output frequency — typically 0–400 Hz — directly controls motor speed. At 50 Hz, the motor runs at nameplate RPM; at 25 Hz, it runs at half speed.
Result: you can run a 415 V-rated three-phase motor from a standard Australian domestic or single-phase workshop supply without rewiring your switchboard for three-phase infrastructure.
Single Phase 240V to Three Phase — How the Voltage Works
Australian three-phase motors are rated at 415 V line-to-line (star/Y connection) or 240 V line-to-line (delta/△ connection). A single-phase VFD with 240 V input produces three-phase output at approximately 240 V. To use this with a standard 415 V motor, reconnect the motor in delta (△) configuration at the terminal box — the motor then draws 240 V and runs at full rated power. All standard IEC-frame motors with a 6-terminal box support this reconnection. Which VFD Size Do You Need?
| Motor Rating | Minimum VFD Size | Recommended VFD Size | Input Current Draw | Typical Application |
|---|---|---|---|---|
| 0.75 kW / 1 HP | 0.75 kW | 1.5 kW | ~6 A | Small bandsaw, bench grinder |
| 1.5 kW / 2 HP | 1.5 kW | 2.2 kW | ~12 A | Small lathe, drill press |
| 2.2 kW / 3 HP | 2.2 kW | 3.7 kW | ~18 A | Medium lathe, small air compressor |
| 3.7 kW / 5 HP | 3.7 kW | 5.5 kW | ~28 A | 10 CFM air compressor, milling machine |
| 5.5 kW / 7.5 HP | 5.5 kW | 7.5 kW | ~40 A | Large workshop compressor, bandmill |
| 7.5 kW / 10 HP | 7.5 kW | 11 kW | ~55 A | Industrial pump, conveyor |
The 1.2× sizing rule: Always select a VFD rated at least 1.2× the motor's nameplate kW. Single-phase input draws roughly double the current of three-phase input at the same load — so a 15 A single-phase circuit limits you to approximately a 1.5 kW motor under continuous load.
VFD vs Static Phase Converter — Which Is Worth the Money?
| Feature | VFD / VSD | Static Phase Converter |
|---|---|---|
| True three-phase output | ✓ Yes | ✗ Simulated (unbalanced) |
| Variable speed control | ✓ 0–400 Hz | ✗ Fixed speed only |
| Motor protection | ✓ Overload, over-temp, phase-loss | ✗ None built-in |
| Soft-start capability | ✓ Eliminates startup surge | ✗ Full inrush on start |
| Price (1.5 kW unit) | ~AU$327 | ~AU$180–250 |
| Long-term motor wear | Lower (smooth voltage) | Higher (unbalanced phases) |
Break-even math: a static converter costs ~AU$80 less upfront for a 1.5 kW application, but unbalanced three-phase supply reduces motor efficiency by 5–10% and shortens bearing life. Over a 5-year period on a compressor running 4 hours/day, the VFD's efficiency advantage recovers the price difference in under 18 months.
Common Applications at HankeMotor
- Workshop machinery: lathes, milling machines, bandsaws — run existing three-phase machines from a single-phase shed supply
- Air compressors: soft-start reduces motor stress on 2.2–7.5 kW piston and screw compressors
- Irrigation pumps: variable speed matches flow to demand, reducing energy use
- Conveyor belts: adjustable speed for production lines and packaging
- Exhaust fans and air blowers: speed control reduces noise and energy at partial load
Australian Market Warning — 240V vs 220V Imports
Many VFDs on eBay and AliExpress are rated for 220 V input (European and Chinese standard), not 240 V (Australian standard). Running a 220 V unit on 240 V supply increases internal component stress and heat. HankeMotor's Folinn H-series drives are factory-configured for 240 V Australian input.
Is a VFD Wrong for Your Situation?
Questions? Call 0401 634 280 or email hankemotors@gmail.com. Our Glen Waverley team can match you with the right drive for your motor and application.