Evidence to watch
The function is proved by changed behavior, not by a parameter value alone.
- Source-selection parameter
- Digital input or control word
- Ready, running and at-speed status bits
F-20 · vendor-neutral function
VFD Run Command Sources
A VFD run command can come from the local keypad, hardwired terminals or a fieldbus control word. The selected source must match the signal the PLC or operator is actually sending.
Why it matters
The behavior behind the parameter.
A drive can be healthy and ready yet ignore a perfectly good terminal because it is listening to the keypad or network. Separating command source from speed-reference source is the fastest way to diagnose that symptom.
- Command source decides where start, stop and direction come from.
- Reference source independently decides the requested speed.
- Local/remote transfer should have an explicit handover and restart policy.
Interactive proof
Test vfd run command sources in three passes.
Keep the motor, load and starting condition constant. Change one function at a time, then use the electrical and mechanical evidence to explain the result.
- 01
Prove a local keypad start at low speed.
- 02
Select terminals and compare 2-wire and 3-wire behavior.
- 03
Select fieldbus, inspect the control word, then interrupt communications and observe the configured response.
Common commissioning mistakes
These errors can make a healthy drive appear faulty or create a misleading test.
- Changing the speed reference when the missing signal is the run command.
- Leaving a local command active during remote handover.
- Ignoring the communication-loss action.
Primary technical references
Transfer the concept; verify the exact drive.
This guide uses vendor-neutral terminology. For real equipment, use the manual for the installed model, option cards and firmware, plus the machine risk assessment and approved commissioning procedure.
Related VFD functions
F-20
VFD 2-Wire vs 3-Wire Control
A 2-wire VFD command follows a maintained contact: closed means run and open means stop. A 3-wire circuit uses momentary start and stop inputs; the drive latches the run request after the start pulse is released.
Read and test F-23VFD Speed Reference Sources
The speed reference is the requested output frequency or process demand. It can come from the keypad, 0–10 V, 4–20 mA, preset speeds, a motorized potentiometer, PID output or a fieldbus word.
Read and test F-22VFD Stop Modes: Ramp, Coast, Quick Stop and DC Brake
A VFD can ramp the frequency down, remove torque and coast, use a faster quick-stop ramp, or apply DC injection braking. Each produces a different current, torque, stopping time and DC-bus response.
Read and testFrom explanation to evidence