A variable frequency drive (VFD) controls an AC motor’s speed. A programmable logic controller (PLC) decides when equipment should run based on inputs and programmed logic. JCR’s eight-hour VFD & PLC class helps electricians follow that sequence when a pump won’t start, a conveyor stops, or a drive ignores a speed command.
VFD, PLC and HMI: what’s the difference?
| Device | Job | Example |
|---|---|---|
| VFD: variable frequency drive | Controls an AC motor’s operating speed by changing its output frequency, with voltage control suited to the motor. | A pump speeds up when the process needs more flow. |
| PLC: programmable logic controller | Reads inputs and runs logic that controls outputs. | A conveyor runs only when the required conditions are satisfied. |
| HMI: human-machine interface | Shows machine information and gives the operator controls. | A screen displays a fault or lets an authorized operator choose a setpoint. |
One symptom can involve all three. “The motor won’t run” doesn’t tell you whether the problem is incoming power, a drive fault, a missing command or an unsatisfied control condition.
What JCR’s class covers
JCR’s VFD & PLC class covers drive setup, acceleration and deceleration ramps, input/output wiring, fault codes and reading PLC logic. You look at the VFD, PLC and HMI as parts of one system.
Bring your 2020 NEC. You can also bring a question from your own work: a recurring drive fault, a missing run command or a confusing sequence of operation. Knowing the equipment model and what happened immediately before the fault makes that discussion more useful. For programming on a particular PLC platform, ask about separate equipment-specific training.
Bring your motor-control questions to class
JCR’s VFD & PLC class costs $230 and includes eight NC classroom CE hours, Board reporting and a free eight-hour self-paced online course. Check the schedule for the location and date that fit your renewal.
Studying for a license? JCR also offers live Zoom exam prep, self-study and live NC exam prep classes.
A useful troubleshooting exercise
Picture a pump with a healthy incoming supply, a drive showing “ready,” and no run command. Start with the sequence of operation:
- What condition is supposed to start the pump?
- Which input tells the controller that condition exists?
- Are the required start conditions and safety interlocks satisfied?
- Is the controller sending the expected command?
- Is the drive configured to accept that command source?
Check the sequence against the manufacturer’s instructions and your employer’s approved troubleshooting procedure. Keep interlocks in service. A missing start condition may be preventing unsafe operation.
Where the NEC fits
In the 2020 NEC, Article 430 covers motors and motor circuits. Part X addresses adjustable-speed drive systems. Don’t assume a drive circuit is sized exactly like a motor connected directly across the line. Read the applicable drive requirements and equipment ratings.
It helps to review motor short-circuit and ground-fault protection and motor overload protection before class. They perform different jobs.
A stopped motor isn’t proof of an electrically safe condition. Drives can contain stored energy. Isolation, discharge time and absence-of-voltage verification must follow the applicable procedure. OSHA’s electrical safe-work requirements address deenergizing and stored electrical energy.
Class questions
Do I need PLC programming experience?
No. The class starts with VFD and PLC fundamentals, so beginners are welcome. If you need training on a particular PLC platform or programming language, ask JCR about that need before choosing a class.
Does the class count for NC continuing education?
Yes. JCR’s VFD & PLC class provides eight NC classroom CE hours under course 6097. JCR reports your completion to the Board. For another state’s credit, check the approvals on the class page.
Is this an electrical safety certification?
No. Technical controls training and electrical safety training address different needs. JCR also offers NFPA 70E training for crews.
Class details and references checked October 25, 2026. Check the selected class for its date, location and CE approval.
