Integrated Motors & Controls Project

Integrated Motors & Controls Project

What This Lab Asks of You

This capstone lab brings together every skill you have built in Motors & Controls: schematic reading, contactor and overload relay sizing, variable frequency drive (VFD) programming, pilot device wiring, and safe work practice. You will design, build, test, and explain a complete motor control system — a full-voltage reversing magnetic starter combined with a VFD speed-control circuit — from a written project specification, exactly as an electrician would on a job site.

The System You Will Build

Your project has two coordinated sections on one training panel:

Section 1 – Reversing Magnetic Starter. A reversing starter uses two contactors wired so that only one can energize at a time. When the forward contactor closes, it connects the three-phase supply (L1-L2-L3) to the motor terminals (T1-T2-T3) in one phase sequence. The reverse contactor swaps two of those phase connections (commonly T1 and T3), reversing motor rotation. Mechanical and electrical interlocking between the two contactors is mandatory — mechanical interlocking through the contactor hardware prevents both contactors from closing simultaneously, and electrical interlocking through normally-closed auxiliary contacts in the control circuit provides a second layer of protection. Your control circuit must provide jog, forward, and reverse functions from a push-button station. An overload relay protects the motor from sustained overcurrent; it is sized to the motor's full-load ampere (FLA) rating per NEC Article 430.

Section 2 – VFD Speed Ramp. A variable frequency drive converts the AC supply to DC internally, then synthesizes a new AC output at a controlled frequency. Raising the output frequency raises motor speed; lowering it reduces speed. Your VFD circuit is triggered by a pilot device of your choice — a selector switch, float switch, or pressure switch are common options. You will program the VFD's acceleration and deceleration ramp times per the specification sheet. Keep VFD input and output wiring in separate conduit or cable runs from control wiring to reduce electrical noise. Follow the manufacturer's manual for all parameter settings; never exceed the motor's nameplate voltage or current rating.

Planning Before You Touch Hardware

Your first deliverable is a complete bill of materials, a schematic (ladder logic style), and a connection wiring diagram. The schematic shows the logic of the circuit — coils, contacts, overloads, and pilot devices arranged in rungs. The wiring diagram shows the physical connections between terminals. These two documents must agree with each other and with the NEC before you request materials.

NEC Article 430 governs motor branch-circuit conductors, overload protection, and short-circuit and ground-fault protection. Size the branch-circuit conductors at no less than 125% of the motor FLA. Size the overload relay element to the FLA as listed in NEC Table 430.52 and the overload device tables guide you on maximum ratings. Record every calculation — your written summary will be graded on them.

Lockout/Tagout — Every Time

Lockout/tagout (LOTO) is not optional and not abbreviated for a training panel. Before any wiring change:

1. Notify affected persons.

2. Identify every energy source — electrical supply to both the starter circuit and the VFD input.

3. Shut off the disconnect or breaker.

4. Apply your personal lock and tag.

5. Attempt to start the equipment to verify zero energy.

6. Verify zero voltage with your meter at the terminals you will touch.

When work is complete, remove tools and materials, restore guards, notify affected persons, then remove your lock and tag. Your instructor must sign off on a pre-energization inspection before every energization. This is a hard stop — no exceptions.

Commissioning and Testing

Once the instructor approves, energize and test each function in sequence:

• Verify motor rotation direction for forward and reverse.
• Test jog function — motor should run only while the jog button is held.
• Verify electrical and mechanical interlocks prevent simultaneous contactor closure.
• Test VFD pilot device: trigger the pilot device and observe the motor accelerate along the programmed ramp; remove the trigger and observe deceleration.
• Measure and record line current with a clamp ammeter at each test condition; compare to calculated FLA and expected values.
• Measure motor shaft speed with a tachometer at minimum and maximum VFD output frequency; compare to nameplate synchronous speed calculations.
• Simulate a fault (instructor-directed) and document the fault code or symptom and the corrective action you take.

Written Summary and Oral Defense

Your one-page summary must include: NEC sizing calculations with code references, the LOTO procedure you performed step by step, a table of measured versus expected values, and a description of any faults and corrections. Be concise and specific — vague answers will not earn full rubric credit. The ten-minute oral defense will ask you to explain your design choices and safety steps. Know your schematic well enough to trace any rung from memory.

Connecting to Your Credentials

NCCER Electrical Levels 3 and 4 assess motor control wiring and VFD operation directly. State Journeyman licensing exams test NEC Article 430 calculations. OSHA 10 emphasizes the hierarchy of controls — LOTO is an administrative and engineering control that protects you from the most dangerous hazards in this lab. Every step of this project maps to a credential you will earn.