Technical Sourcebook
Field-oriented guides on industrial motor control, wiring standards, and electrical theory. Each entry is paired with a simulator for hands-on practice of the concepts.
Wire a 3-Wire Motor Control Circuit Free Online
The 3-wire start/stop circuit latches through a seal-in contact. Trace current in all three states and wire it yourself in a free browser trainer.
How to Wire a Motor Starter (3-Phase, NEMA)
Power circuit, control circuit, seal-in contact, and OL protection — wire a NEMA Size 1 motor starter from L1 to T3. Free interactive wiring practice.
Motor Starter Internal Wiring: 3 Factory Jumpers
NEMA starters ship with three internal jumpers for coil return, seal-in, and OL protection. Where each one goes and why it matters.
NEMA vs IEC Overload Relay Placement Explained
The 95-96 OL contact sits on opposite sides of the coil in NEMA and IEC starters. Return-side vs hot-side — and the engineering reason behind each.
Motor Control Simulator — Wire Circuits Free in Your Browser
Wire motor control circuits from scratch in a free browser trainer. Route cables, press buttons, measure voltage with a multimeter, and find faults.
Measure Voltage on a Control Circuit: Step-by-Step
Anchor to L2 or X2, probe each terminal in sequence, find the open. Measurement procedure, reading interpretation, and free multimeter practice online.
How to Read a Ladder Diagram
Rails, rungs, contacts, coils — read a motor control ladder diagram from L1 to L2, trace current flow, and connect the schematic to the power circuit.
How to Reverse a 3-Phase Motor (Swap Two Leads)
Reverse a 3-phase motor by swapping two phase leads. Why it works, the two interlocks that stop a phase-to-phase short, and where the OL relay goes.
Normally Open vs Normally Closed Contacts Explained
NO contacts close when actuated; NC contacts open. Why STOP is NC, START is NO, and how the normal state of every contact determines circuit behavior.
What Is a Control Transformer? Sizing and Fusing
A control transformer steps line voltage down to a safe control voltage, typically 120V or 24V. What it does, sizing it in VA, and NEC 430.72(C) fusing.
What Is a Jogging Circuit? Run a Motor in Pulses
A jogging circuit bypasses the seal-in so the motor runs only while you hold the button — for inching and positioning. Two methods, wired interactively.
What Is an OL Trip and How Do You Reset One?
An overload relay trips when motor current exceeds the heater rating. How OL relays detect overcurrent, why the 95-96 contact opens, and how to reset.
Overload Relay Keeps Tripping? How to Diagnose It
The relay is the messenger, not the fault. Read the trip pattern, then check supply voltage, motor current, heater sizing, and ambient temperature.
Motor Starter Manual Operator: What It Does
The manual operator closes the contactor without energizing the coil. Bump testing splits power faults from control faults — and what it cannot tell you.