Every drive commissioning starts with a choice most people leave at default: control mode. The default is often fine — and sometimes it quietly costs you product quality.
The short physics
V/f (scalar) holds a voltage-to-frequency ratio and trusts the motor to follow. Simple, robust, tolerant of bad motor data — and soft: torque at low speed is weak, speed accuracy is slip-dependent, and response to load steps is leisurely. Perfect for fans, pumps and anything with quadratic load.
Vector control models the motor and controls flux and torque separately. Open-loop (sensorless) vector gets you solid torque from a few Hz upward and decent dynamics — enough for conveyors, mixers, extruders. Closed-loop vector with an encoder adds true zero-speed torque, tight speed accuracy and fast response — the territory of hoists, winders, presses and positioning.
Field rules
- Quadratic loads: V/f, and enable the energy-optimizing feature drives offer in this mode.
- Constant-torque machinery without precision demands: sensorless vector, with a proper motor identification run — vector without ID data is worse than honest V/f.
- Holding loads at standstill (hoists), web tension, synchronized sections: encoder, no negotiation.
- Multiple motors on one drive: V/f only — vector control needs one motor model, not a choir.
FAQ
Why does my sensorless vector drive hunt at 2 Hz? Below a few Hz the model runs out of signal. Improve ID data, or accept that sustained low-speed torque wants an encoder.
Does vector mode save energy on a fan? No meaningful amount — the quadratic load curve is where fan savings live, and V/f rides it fine.
Zone Otomasyon commissions drives with the control mode the load deserves. Drive selection help.