Third year14 items · about 3 hours
Third-year electrical apprentice
Third year is where the trade turns three-phase. These lessons take wye and delta apart, build transformer banks, spin up an induction motor and start it five ways, turn a relay circuit into PLC ladder logic, and then walk the commercial jobsite — protection, grounding, wiring methods, prints and fire alarm. Each lesson ends in a short quiz; pass it at 80% and it is ticked off here.
Comes after: First year · Second year
The lessons, in order
- Wye and delta: line vs phase The two ways three windings are joined, and the √3 that separates line from phase voltage and current.
- Unbalanced loads and neutral current Why a balanced wye neutral carries nothing, what it carries when the loads are uneven, and the harmonics that break the rule.
- Three-phase power and power factor kW, kVA and kVAR on a three-phase load: the power triangle, the √3 formula and what a poor power factor costs.
- Three-phase transformer connections Delta-wye, wye-wye, delta-delta and wye-delta: what each gives you on the secondary and where you meet it.
- Polarity, phase shift and open delta Additive and subtractive polarity, the 30° shift through a delta-wye, and running a bank on two cans.
- How an AC induction motor works The rotating field, synchronous speed, slip, and reading the nameplate numbers that come out of them.
- Motor starting methods Across-the-line, primary resistor, autotransformer, wye-delta, soft starter and drive — what each trades away.
- Intro to PLCs: from relays to ladder logic Inputs, outputs, the scan cycle, and how a hard-wired start/stop becomes three rungs of ladder logic.
- Overcurrent protection and coordination Overload versus short circuit, reading a time-current curve, and what "selective coordination" is trying to do.
- Grounding and bonding as a system System grounding, equipment bonding, the fault return path and separately derived systems, end to end.
- Commercial wiring methods EMT, rigid, flex, cable tray, armoured cable and busway — what each is good at and the questions to ask of the book.
- Reading commercial and industrial prints The drawing set, single-lines, risers, panel and luminaire schedules, and finding your way around a sheet.
- Fire alarm basics Initiating and notification devices, supervision and end-of-line devices, conventional versus addressable.
- Third-year review quiz Every third-year question in one place, mixed, with explanations. Filter to a topic you are weak on.
Tools for this year
- Three-phase power calculator kW, kVA, kVAR and amps from any one of them, with voltage and power factor — three-phase or single.
- Transformer full-load current & ratio Primary and secondary full-load amps, line and turns ratio, and the current in each winding for delta or wye.
- Motor synchronous speed & slip Synchronous speed from frequency and poles, the pole count a nameplate speed implies, slip and rotor frequency.
- Delta ↔ wye impedance conversion Turn a delta of three impedances into the equivalent wye, or back — balanced or not.
How to use this year
Go in order the first time — each lesson leans on the one before, and the three-phase lessons at the top feed everything after them. Every number on these pages is physics or a practice figure; ratings, sizes and limits come from your own code book (CSA C22.1 in Canada, the NEC in the US), which is the book your exam uses. When a topic has a hands-on side, the lesson points you at the motor control labs or one of the tools above.
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A heads-up on tools that fit — by email, optional
Leave your email and tick the box for a short heads-up, at most every two weeks, about tools, drills and diagrams that fit what you've been working through — here and on bentright.com and fieldcalc.net. One list across the three, one click to leave, and nothing is sent until you confirm from your inbox.