Industrial Engineer · phase 11 of 16
Open-Loop Control
Motor control without direct shaft-speed or position feedback from an encoder.
The Explain card
- Plain English
- Open loop means the drive commands a frequency and trusts the motor to follow. There is no encoder telling it what the shaft is actually doing.
- Example
- A fan drive is told 45 hertz and applies 45 hertz. If the belt slips or the load changes, the drive never knows, and the fan simply runs at whatever speed results.
- Why it matters
- Open loop is cheaper, simpler and good enough for most fans, pumps and conveyors, where a few percent of speed error is fine. It is the wrong choice where speed must be exact, where full torque is needed at zero speed, or where the load can drive the motor.
- Hook
- Command the speed and hope.
Where it sits in the deck
Phase 11: VFD Control Modes and Tuning
How a drive decides what to send the motor, from plain volts per hertz up to closed loop vector control, and how each mode is tuned.
