VFD plus diesel generator: how it differs from grid power
Since 2022 "VFD for a generator" has been one of our most frequent requests. Typical customer: a pump station on a remote site, a farm, a service garage with its own 10-50 kVA generator. The problem: a VFD pushes harmonics back into the supply, the generator hunts, and trips on overvoltage or protection. The fix: pick a VFD with active PFC (Power Factor Correction) on the input, add a sine filter on the output, and size the generator at 1.5-2x the sum of loads. The drives that run most reliably from our stock are Veichi AC310 with PFC and INVT GD200A/GD350A with a built-in sine option. Premium tier is Danfoss FC302 with a full sine filter.
How we size the generator for a VFD
We ask the customer three things. One: motor power (off the nameplate, kW or kVA). Two: generator model and rated output (kVA, not kW; synchronous or inverter type). Three: how the motor starts (soft via VFD is fine; direct-on-line bypassing the VFD needs 4-5x the motor power on the generator). Rule of thumb: generator (kVA) = VFD (kW) x 1.5-2.0. An 11 kW VFD wants a 17-22 kVA generator. Inverter petrol generators in the 5-10 kW range do not get along with VFDs without a filter: use a synchronous diesel or always add a sine input filter. Warranty 12-24 months, shipping from Kyiv in 1-3 days.
Popular brands for generator startup tasks
Based on 12-month sales data: Veichi, Delta Electronics, INVT, Danfoss, Mitsubishi Electric.
Useful preset pages: single-phase 220V, three-phase 380V, vector control drives.
Filter by key parameters
Quick filters: 0.75 kW, 1.5 kW, 2.2 kW, 1x220 V, 3x380 V.
FAQ
What generator margin is recommended for a VFD?
Typically 25-35% above drive nominal power, and up to 40-50% for hard-start loads.
Can a VFD run with fluctuating generator voltage?
Yes, if protection thresholds and acceleration ramps are configured correctly.
V/F or vector control for generator supply?
V/F is often enough for pumps and fans; vector control is preferred for demanding torque conditions.
Why does the generator drop during startup?
Most cases are caused by insufficient generator reserve or too aggressive acceleration settings.
Warranty, support, payment and delivery
We help with model selection, generator compatibility checks, and commissioning support. Nationwide delivery across Ukraine with VAT invoicing available.
