Scalar (V/f) VFD: when to take it, when you need vector
Scalar V/f control is the simplest and cheapest VFD logic: proportional change of voltage and frequency by a linear or quadratic law. No feedback, no torque-by-speed, no precise speed holding under load. Enough for 70% of household and simple industrial jobs: centrifugal pumps, fans, augers without overload, conveyors with even belt flow. Typical customer this year: a farmer with an irrigation pump, a hotel with supply ventilation, a service station with a low-pressure compressor.
When V/f does not fit: cranes, hoists, centrifuges (where torque must be held at low speed with encoder feedback), machine-tool spindle drives (0.1% speed accuracy required), servo motors. For these we ship vector models with sensorless vector or with PG (encoder). Note: the line is fuzzy, there is a middle ground: a shock-load compressor on a scalar GD200A holds, but on complex jobs saving on scalar costs feature shortage within a year.
Which models we ship most often
From daily stock. INVT GD10 (0.7-2.2 kW): compact scalar drive for small household and light industrial jobs, in stock monthly. INVT GD200A (4-160 kW): powerful line with V/f and without on-board sensorless vector, for water supply, ventilation, simple machine tools. ABB ACS150 (0.4-4 kW): premium ABB equivalent, works as a V/f-only drive without vector mode, more expensive than INVT but with 2-year warranty and European support. Allen Bradley PowerFlex 4 (0.7-2.2 kW): rare SKU for North-American integrations, ship to order.
Before paying we clarify. First: load type. Pump/fan with quadratic characteristic: V/f no problem. Conveyor with 50% starting torque: V/f is enough. Crusher, centrifuge, crane: need vector, not this category. Second: speed accuracy. If the customer says "hold 750 rpm within 5 rpm under variable load", V/f will not deliver, need vector. Third: warranty and support. Budget: INVT GD10/GD200A. Premium: ABB ACS150. 1-3 day delivery from our Kyiv warehouse, 2-year warranty.
Manufacturers in our stock
- INVT (GD10, GD200A): universal scalar, in stock
- ABB (ACS150): premium scalar drive for simple jobs
- Allen Bradley (PowerFlex 4): rare SKU, ship to order
- Bosch Rexroth (EFC 3600, EFC 3610, VFC 3610): Europe, specific applications
