REE: Circuits, Machines, and Power Systems

REE circuits and machines is the heart of the Registered Electrical Engineer licensure exam. The third paper — Electrical Engineering Professional Subjects — pulls heavily from circuit analysis, electric machines, and power systems. It's the longest paper, the most calculation-heavy, and the one that most determines whether your general average clears 70%. Reviewers who memorise without practising live calculations come unstuck under exam pressure.

The next REE board sitting is September 5–6, 2026. The PRC Board of Electrical Engineering runs it bi-annually — April and September — with around 10,000 candidates per year. Pass rates hover around 55–60%.

What the Paper Covers

The REE board exam splits into three subjects under PRC Resolution 2113 s.2025. The third paper — Electrical Engineering Professional Subjects — is the largest. Topic mix:

• DC and AC circuit analysis — Kirchhoff's laws, mesh and nodal, AC steady state, three-phase. Around 20–25 items.
• Transformers — single-phase, three-phase, equivalent circuit, regulation, efficiency. Around 12–15 items.
• Induction motors — equivalent circuit, slip, torque-speed, starting, control. Around 10–12 items.
• Synchronous machines — generators and motors, voltage regulation, parallel operation. Around 8–10 items.
• DC machines — generators and motors, characteristics, control. Around 5–8 items.
• Power systems — transmission line parameters, fault analysis, per-unit system. Around 10–12 items.
• Protection and control — relays, circuit breakers, coordination. Around 5–8 items.
• Illumination and electrical wiring — Philippine Electrical Code (PEC). Around 5–8 items.
• Electronics fundamentals — diodes, BJTs, op-amps. Around 5 items.

The Recurring Problem Archetypes

Three-Phase Circuit Analysis

Wye-wye, wye-delta, delta-delta connections. Line vs phase quantities. Power calculations using line values. Around 3–4 items per cycle. The trap is forgetting the √3 factor when converting between line and phase.

Single-Phase Transformer Equivalent Circuit

Open-circuit and short-circuit tests. Calculate equivalent resistance and reactance referred to primary or secondary. Voltage regulation at given power factor. Around 2–3 items. Drill the per-unit conversion as well.

Three-Phase Transformer Banks

Wye-delta, delta-wye connections. Phase shift between primary and secondary. Around 1–2 items.

Induction Motor Performance

Slip given. Calculate rotor frequency, rotor current, developed torque, efficiency. The torque-slip curve. Around 3–4 items per cycle. Memorise the equivalent circuit and the relationship between slip and rotor copper losses.

Synchronous Generator Voltage Regulation

Synchronous reactance given. Calculate excitation EMF for a given load. Voltage regulation. Around 2 items.

Transmission Line Parameters

Series impedance and shunt admittance per unit length. Short, medium, long line classifications. ABCD parameters. Around 2 items.

Symmetrical Fault Analysis

Three-phase fault on a power system. Per-unit conversion. Fault current calculation. Around 1–2 items.

Where Reviewers Leak Points

• Per-unit base mismatch — using one MVA base for the system but forgetting to convert transformer reactance to that base. Common trap.
• Power factor sign convention — leading vs lagging. Capacitive vs inductive. Sketch the phasor on every problem.
• Slip calculation — synchronous speed minus mechanical speed, divided by synchronous speed. Easy to slip the sign under pressure.
• PEC code references — the controlling code is the latest Philippine Electrical Code. Don't drill from older editions.

An 8-Week Plan

1. Weeks 1–2 — DC and AC circuit fundamentals. Three-phase systems. 80 problems.
2. Week 3 — Transformers. Single-phase and three-phase. 50 problems.
3. Week 4 — Induction motors. 50 problems.
4. Week 5 — Synchronous and DC machines. 50 problems.
5. Week 6 — Power systems. Transmission, fault analysis, per-unit. 50 problems.
6. Week 7 — Protection, illumination, PEC, electronics. 60 problems.
7. Week 8 — Mock papers. Two minimum.

The Per-Unit System

Master this. Around 5–8 items per cycle hinge on per-unit conversion done correctly.

Why Per-Unit

It normalises calculations across multiple voltage levels in a power system. A transformer's per-unit impedance is the same on either side. Per-unit fault currents simplify cross-system analysis.

The Conversion Rules

• Choose a base MVA and base voltage on one side of the system.
• Base current = base MVA / (√3 × base voltage line) for three-phase.
• Base impedance = base voltage line² / base MVA.
• Per-unit impedance = actual impedance / base impedance.
• To convert per-unit between bases, multiply by (new MVA / old MVA) and (old kV / new kV)².

Drill the conversion until automatic. Items often present a transformer rated on one MVA base and ask for fault current on a different system base.

Power System Protection

Around 5–8 items. The high-yield topics:

• Overcurrent relays — definite-time, inverse-time, instantaneous. Coordination with downstream relays.
• Differential protection — for transformers and generators. Restraining and operating coils.
• Distance protection — for transmission lines. Zone reach and timing.
• Circuit breaker ratings — interrupting capacity, BIL, voltage class.

Illumination and PEC

Around 5–8 items. The Philippine Electrical Code carries the bulk of these. The PEC blocks tested most:

• Conductor sizing — ampacity tables, voltage drop calculations.
• Branch circuits and feeders — load calculations.
• Grounding — equipment grounding, system grounding.
• Motor circuits — overload and short-circuit protection.
• Illumination — lumen method, point-by-point method, recommended levels.

How This Subject Connects to the Other REE Papers

The REE board has three papers. The first tests math and engineering sciences. The second tests engineering sciences and allied subjects. The third — this one — tests the professional electrical engineering subjects.

Cross-references matter. Calculus from paper one feeds the AC steady-state analysis. Statics from paper two feeds the mechanical aspects of machine design. Drill in parallel.

Where REE Differs From Other Engineering Boards

REE is the most calculation-heavy of the four engineering boards. The CELE has heavier individual structural problems but lower problem density per paper. The ME blends thermodynamics with design. The ECE blends communications theory with applications. REE is sustained calculation across circuits, machines, and power systems — and the per-unit system threads through everything.

That makes pacing critical. Aim for 90 seconds average per item, with the harder transformer and machine problems taking up to three minutes. Drill mock papers under timed conditions.

How Super Tutor Drills REE

Our REE Electrical Engineering track runs subject-tagged practice across all three REE papers. Professional subject items are split by domain — circuits, transformers, motors, generators, power systems — so you can see exactly which block is dragging your average. Every item carries a worked rationale that walks the per-unit conversion, the phasor diagram, and the common trap. The Focused Yearly tier is ₱1,999/year, around 80% less than equivalent classroom review.

For broader context, see the engineering board review pillar. For cross-domain context, electronics reviewers can compare the AC analysis block with the ECE electronics systems guide. Mechanical reviewers can cross-reference the motor materials selection block with the ME machine design guide. STM's grade 12 electrical engineering page and grade 11 mathematics page backfill the foundational topics. The PRC Board of Electrical Engineering publishes the current TOS — confirm before each cycle.

FAQ

How heavy is per-unit on the paper?

Threaded through the power systems and transformer blocks — easily 8–10 items hinge on per-unit done correctly. Drill it cold.

Is the PEC tested in detail?

Around 5–8 items. Conductor sizing, voltage drop, motor circuits, grounding. Read the latest PEC edition once and drill the recurring chapters.

Are electronics fundamentals heavy?

No. Around 5 items at the introductory level. Diodes, BJTs, op-amps in basic configurations. Don't over-prep.

What's the worst trap?

Per-unit base mismatch. The cleanest path is to set the base, convert all impedances at the start, then run all calculations in per-unit.

What to Do This Week

• Engineering Board Review Pillar
• ECE Electronics Systems Strategy
• ME Machine Design Strategy
• Super Tutor's REE Track