The Transformer Sandbox for Linemen
Build transformer bank connections from scratch. Wire them however you want. Hit Energize to instantly see your secondary voltages. Get it right — or get it wrong on purpose.
No textbook lectures. No multiple choice quizzes. Just wire it up, see the results, and learn by doing.
Drop single-phase cans with actual H1/H2 and X1/X2/X3 terminals. Set primary voltage, kVA, and polarity — just like reading a nameplate.
Energize and get secondary voltages in realtime. Change a wire while it's live and the results update immediately. No waiting, no lag.
Every hookup gets classified: VALID, FLOATING, or FAULT. The app highlights exactly which wires cause the problem.
3-phase: AB, BC, CA plus phase-to-neutral. Split-phase: L1-L2, L1-N, L2-N. All values in RMS — just like your meter reads.
From a clean canvas to energized results — every connection is computed, not looked up.
Tap terminals to connect wires. Build the connection from scratch — no presets, no hand-holding.
Hit Energize and instantly see secondary voltages. Familiar numbers like 120/240V — computed from your actual wiring.
Wye, Delta, Open — build them all from individual cans. Wire it wrong on purpose and see what actually happens.
Shorts and conflicting connections are caught and highlighted. Learn from mistakes without consequences.
Build all of these from individual cans. Plus anything else you can dream up.
| Connection | Transformers | Typical Output |
|---|---|---|
| Wye–Wye | 3 cans | 208Y/120 or 480Y/277 |
| Delta–Delta | 3 cans | 240 3-wire |
| Delta–Wye | 3 cans | 208Y/120 or 480Y/277 |
| Wye–Delta | 3 cans | 240 3-wire |
| Open-Wye / Open-Delta | 2 cans | 240/120 with wild leg |
| Open-Delta / Open-Delta | 2 cans | 240 3-wire (reduced kVA) |
| Single-phase | 1 can | 120/240 split-phase |
Delta or Wye. Choose from common primary voltages — 4.16 kV to 34.5 kV — or enter a custom value.
Set the nameplate: primary voltage, kVA rating, polarity. Toggle series or parallel secondary.
Tap terminal to terminal. Build any connection you want — standard or experimental.
See voltages instantly. Change something — the results update live. That's it.
Build the hookups from your training book and verify them. Then try the wrong way and see what happens.
Brush up on connections you haven't done in a while. Try that weird configuration your buddy told you about.
Demonstrate why polarity matters, what open-wye does to the wild leg, or what happens when you short two phases.
Top Hand uses a phasor-domain circuit solver — the same kind of Modified Nodal Analysis (MNA) used in engineering simulation tools. Every result is computed from your actual wiring.
You can wire up any combination and the solver computes the real resulting voltages — including all the weird ones that come from mistakes.
$9.99. Offline. No account needed. If you can read a transformer nameplate, you can use this app.
Download on the App Store