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Three-phase delta (Δ)

Power, transformers and three-phase · Advanced · about 20 minutes · part of Zen’s Electronics Design Mastery

In a delta each load sits directly between two lines, so it sees the full line voltage. Each line current is the phasor difference of two load currents, √3 times a load current when balanced.

Three-phase delta (Δ): the circuit on the simulator's bench

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How it works

In a delta, Vload = Vline = 220 V

Iphase = Vline / Rlamp = 181.8 mA

Iline = I12 − I31 (phasors) = √3 · Iphase = 314.9 mA when balanced. P = 3 · VL · Iph = 120 W

Try it on the bench

  1. Switch the supply to 230/400 V. The 240 V lamps now get 400 V each and blow. A delta load must be rated for the line voltage.
  2. Change one lamp’s wattage and see I_line / I_phase move away from 1.732.

Parts on the bench

In the course

Zen’s Electronics Design Mastery, module “AC & Reactance”.

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