Top Hand Transformer Lab

Wire it. Energize it. See what happens.

The transformer sandbox built by lineman for linemen.

Ever wonder what happens when you flip a polarity? Hook up an open-wye wrong? Wire a delta-wye backward? Now you can find out — on your phone, no consequences.

Top Hand lets you build transformer bank connections from scratch using single-phase cans, wire them up however you want, and hit Energize to instantly see your secondary voltages. Get it right and you'll see 120/240, 277/480, etc. Get it wrong and troubleshoot the problem.

No textbook lectures. No multiple choice quizzes. Just wire it up, see the results, and learn by doing.

What You Get
Real Transformer Components
Drop single-phase cans onto your workspace with actual H1/H2 and X1/X2/X3 terminals. Set your primary coil voltage, kVA rating, and polarity — just like reading a nameplate. Switch between series and parallel secondary modes and watch what changes.

Instant Results When You Energize
Energize and get secondary voltages in in realtime. Change a wire while it's live and the results update immediately. No waiting, no lag — just instant feedback on every connection you make.

Clear Fault & Status Indicators
Every hookup gets classified:

VALID — Clean voltages, everything checks out
FLOATING / OPEN — Something's not connected, output is undefined
FAULT — Short circuit or conflicting connections.

Voltage Tables That Make Sense
See your results laid out clearly:

3-phase: AB, BC, CA — plus A-N, B-N, C-N when neutral is present
Split-phase: L1-L2, L1-N, L2-N

All values in RMS, just like your meter reads

All Standard Hookups
Build all of these from individual cans — no presets, no hand-holding:

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
Plus anything else you can dream up. Wire it wrong on purpose — that's the whole point.

Built For The Trade
Pick your primary voltage from common system voltages:

4.16 kV
12.47 kV
13.2 kV
13.8 kV
24.9 kV
34.5 kV

Or enter a custom value. The app handles Delta and Wye sources with proper phase relationships — no shortcuts, no fake math.

Polarity matters. Each can shows its polarity marking. Wire an additive can like it's subtractive and you'll see it in the results. That's how you learn what polarity actually does to your voltages.

Series vs. Parallel secondary — toggle it on any can. In parallel mode, X2 disappears because there's no center tap. Any wires connected to X2 get removed automatically (the app tells you). Just like the real thing — you can't land on a terminal that isn't there.

Who It's For
Apprentices — Build the hookups from your training book and verify them. Then try the wrong way and see what happens.
Journeymen — Brush up on connections you haven't done in a while. Try that weird configuration your buddy told you about.
Instructors — Use it in class to demonstrate why polarity matters, what open-wye does to the wild leg, or what happens when you short two phases through a transformer.
What It's NOT
This is a learning simulator, not a field procedures guide.

No step-by-step hookup instructions
No arc-flash calculations
No protection or relay coordination
No substitute for your training, your foreman, or your brain
The app teaches you what happens electrically when you make connections. How you safely do that work on a pole is between you, your crew, and your safety requirements.

Built by a lineman, for linemen. No fluff, no filler — just transformers and voltages.