CEWP Commercial - independent technical foundations cheat sheet
CEWP Commercial - independent technical foundations · Keep the key ideas within reach.
Electrical circuits, machines and digital logic
For a sinusoid V_rms = V_peak/√2; the stated impedance magnitude is for a series RLC model.
Q_C = P(tan φ₁ − tan φ₂) for power-factor correction
Transformer: V₁/V₂ = N₁/N₂ = I₂/I₁
Induction motor: n = (1 − s)·60f/p
Thévenin voltage is open-circuit voltage; deactivate independent sources to obtain resistance while preserving dependent-source behavior.
Karnaugh: give the minimum sum of products
Transformers, machines and distribution-system reasoning
Demand assumptions and nameplate totals describe different quantities.
Real transformers require losses, impedance and actual ratings.
State whether a speed formula uses poles or pole pairs.
An additional source changes fault and operating conditions as well as reliability.
Evaluate lifecycle behavior rather than one component efficiency or initial cost.
Fault models, protective coordination and earthing concepts
Separate prospective fault current, load current and device rating.
Use the proper balanced or unbalanced fault model.
An RCCB alone is not overcurrent protection.
Nominal device ratios do not by themselves prove selectivity.
Earthing does not guarantee zero touch voltage.
Installation planning, measurement and evidence of compliance
Cable selection needs installation conditions and several distinct checks.
Control drawing revisions and review material field changes.
Continuity, insulation, polarity and protection tests are not interchangeable.
An indicator or switch label does not prove absence of every source.
Record actual evidence, limitations and unresolved defects.
Measurement, feedback, PLC and automation
Sensitivity = Δoutput/Δinput; resolution = smallest detectable change
Closed-loop error compares reference and measurement; integral action can remove appropriate steady-state error only under suitable stability and operating assumptions.
PLC scan: read inputs → run program → update outputs
4–20 mA live zero: (I − 4)/16 of the span
Repeatability ≠ accuracy, resolution ≠ sensitivity
Robot DOF come from its joints; workspace is the reachable volume
Lighting models, metering and building-control integration
Lumens, lux, luminance and watts are different quantities.
A lumen-method calculation uses the explicitly stated factors.
Compare energy measures with a defined operating baseline.
A command and a verified physical state are different evidence.
Ordinary BMS integration does not create life-safety approval.
Engineering models, drawings, evidence and project decisions
State the system boundary and assumptions before calculation.
Units, sign conventions and uncertainty are part of the answer.
Verification against a specification differs from validation for an intended use.
Drawings need a declared convention and controlled revision.
Classroom models do not authorize physical operation or structural approval.