Technical reference and worked-example guide
Variable-frequency drive component guide: field reference
Direct answer
The reader can trace one run and speed request through the drive to motor response and separate source selection, trip, STO, motor and process faults.
Written for pLC and maintenance learners understanding what a VFD controls and how power, commands, references, motor data and diagnostics interact.
Definition
Input supply, rectifier, DC bus, inverter, motor data, control source, speed reference, acceleration and deceleration, current limit, braking, STO, feedback and fault history.
Signal path
Supply and command through source selection, internal drive state, modulated output, motor torque and speed, machine load and independent feedback.
Worked example
A bounded start reaches the requested speed and load, stops predictably and records healthy ready, running and feedback states.
Limits
Zero reference, source conflict, overcurrent, undervoltage, overload, motor mismatch, rapid deceleration, STO demand, feedback loss and power return.
Common mistake
A supply, protection, command, reference, parameter, drive, motor, mechanical, feedback or process mismatch.
Verification
The drive sized, wired, parameterized and commissioned on the target motor and machine under approved procedures.
What does a VFD do?
It converts incoming electrical power into controlled motor voltage and frequency so torque and speed can be managed within drive, motor and process limits.
What must a PLC send to a VFD?
The contract may include enable or run command, direction, speed reference and reset, while ready, running, speed, current and fault feedback provide evidence.