Guides
Short, practical explanations for students and technicians. Each guide links to a hands-on exercise in the free PlantFlow 3D simulator.
How a DOL motor starter worksThe direct-on-line starter explained step by step: power circuit, control circuit, seal-in contact, stop button and overload protection.Star–delta starting explainedWhy star–delta starting reduces starting current, how the three contactors and the timer work, and the interlocks that keep it safe.Forward–reverse motor control and interlocksHow swapping two phases reverses a three-phase motor, and the electrical and push-button interlocks that prevent a phase-to-phase short.Motor full-load current and overload settingsHow to calculate a three-phase motor's full-load current, why the nameplate value wins, and how it is used for overload and cable checks.4–20 mA current loops for beginnersWhy industry sends measurements as 4–20 mA, how a 2-wire loop is powered, how to convert mA to engineering units and how NAMUR NE 43 signals faults.PLC ladder logic basicsContacts, coils, latches, timers and counters explained with a real pump control program, and how a PLC scan works.Conventional fire alarm zones and EOL supervisionHow a conventional fire alarm panel detects alarms and cable faults using an end-of-line resistor, and what silence, reset and disable do.Access control: fail-safe and fail-secure locksHow an access controller decides to open a door, the difference between fail-safe and fail-secure locks, and why fire release matters.Reading P&ID instrument tagsHow instrument tag letters describe what is measured and what the device does, with examples like LT, LSHH, PDT and FIC.Instrument loop diagrams and cable screensWhat an instrument loop diagram shows, how a 2-wire loop is wired from field to PLC, and why cable screens are earthed at one end only.Industrial network basics: VLANs, PoE and cable limitsHow plant networks separate control, CCTV and access control with VLANs and a firewall, and the practical limits of copper, fibre and PoE.Variable frequency drives (VFD) explainedHow a VFD controls motor speed, why it starts without inrush current, how its 24 V control inputs work and what to check when it trips.Soft starters: gentle starting for big motorsHow a soft starter limits starting current and mechanical shock by ramping the motor voltage, and how it differs from a VFD.Single-phase capacitor motorsWhy a single-phase motor needs a capacitor, how to reverse it, and how to find a failed capacitor.Automatic transfer switches (ATS) for standby generatorsHow an ATS moves an essential load from the mains to a standby generator and back, and why the two sources must never be connected together.Power factor and capacitor banksWhat power factor means, why motors lower it, and how an automatic capacitor bank brings it back up and reduces the line current.Two-speed Dahlander motorsHow one tapped winding gives two speeds, why a third contactor makes a double star, and why two phases are swapped for high speed.Lighting control with a photocell and a HAND–0–AUTO switchHow outdoor and street lighting is switched automatically by a photocell through a lighting contactor, with a selector for maintenance.Three-phase distribution boards, MCBs and RCDsHow a 400/230 V board feeds single-phase final circuits from three phases, why the neutral current depends on balance, and how MCBs and RCDs protect people and cables.Overload relay contacts 95-96 and 97-98: test, reset and settingWhat the overload relay terminals 95-96 and 97-98 do, how to use the TEST and RESET buttons, manual and automatic reset, and how to set the current dial.How to use a multimeter: voltage, continuity and resistanceA practical guide to measuring AC voltage, testing continuity with the buzzer, reading coil and winding resistance, and using a clamp meter safely in control panels.Troubleshooting a motor control circuit step by stepA safe and logical method to find why a motor does not start or stops: symptoms, visual checks, the voltage trace, and dead testing.Emergency stop circuits: how an E-stop should be wiredHow emergency stop buttons work, why they use normally closed latching contacts, where to wire them, and why releasing an E-stop must not restart a machine.Contactor terminals explained: 1-2, 3-4, 5-6, A1-A2, 13-14 and 21-22How to read contactor terminal numbers, which contacts carry motor current, how the coil is connected, and how auxiliary contacts are used for hold-in and interlocks.Electrical wire colours and wire numbering in control panelsIEC conductor colours for three-phase and control circuits, how wire numbers and ferrules work, and why the same number means the same potential.