Winding skill takes years: HR for transformer manufacturers

The master winder at a transformer works has two years left before he plans to stop. He winds every HV disc coil for the larger units himself. A junior's first attempt on a disc coil comes off the mandrel too tall for the core window, and three days of paper-covered copper go to the scrap bin. The owner realises that the most valuable skill in the building has no understudy.

That is the first pressure point on any transformer floor. Winding is learnt by hand over years, and most works only discover how thin their bench is when someone retires, falls ill or is hired away.

• Tension. The brake on the conductor drum set so turns lie tight without stretching or cracking the paper covering.
• Layer and turn count. Every turn counted and every layer finished square, so the ratio test passes first time.
• Transpositions. Strands swapped at the right point in a multi-strand conductor, without kinking or tearing insulation.
• Insulation placement. Layer paper, pressboard spacers and duct sticks fitted where the design says, clean and dry.
• Coil dimensions. Height and radial build held so the coil slides over the core leg and sits in the window as drawn.
• Tapping leads. Leads brought out, brazed and insulated at the correct turns, ready for the tap changer.

None of these is hard to describe. All of them are hard to do consistently, at speed, on a design the winder has not seen before.

Distribution transformers repeat often, so LV spiral winding on round or strip conductor can be learnt in months. Power transformer coils are another matter. Each order brings a new rating, voltage or conductor size, and a works may build only a handful of each design a year. Repetition, the teacher of any hand skill, is scarce. Errors also show up late. A turn miscount appears at the ratio test, and a slack layer shows after drying, when the coil has shrunk and the unit is already assembled.

• Scrapped conductor and paper whenever a learner spoils a coil without a practice stage first.
• Active parts lifted back out of the tank after a ratio or winding resistance failure, with the oven cycle repeated.
• Test bay queues as units wait for the one winder who can correct a fault.
• Delivery dates that hinge on one person's health, and a master who never takes a full week off.
• A bargaining position the master knows he holds, which tends to end in a poaching offer or a quiet burnout.

1. 1

   Rung 1: Pressboard and preparation

   Cutting spacers and duct sticks, preparing formers and paper, loading the conductor drum. Signed off when the helper prepares a full coil kit without errors.

2. 2

   Rung 2: LV winding on distribution sizes

   Spiral or layer winding on repeat designs under a senior's eye. Signed off on practice coils wound with reject conductor, measured for height and turns.

3. 3

   Rung 3: HV crossover and tapping leads

   Multi-layer HV coils, tap leads brought out and brazed. Signed off when two production coils pass ratio and resistance tests first time.

4. 4

   Rung 4: Disc windings and transpositions

   Disc coils for power units, transposed conductor, spacer placement. Signed off by the master on a production coil he has inspected turn by turn.

5. 5

   Rung 5: Setting up a new design

   Reading the design sheet, choosing formers, setting tension and planning the winding sequence. The rung that makes someone a successor rather than a pair of hands.

Each rung carries a pay step, and the transformer learning and development page shows how the sign-offs sit in a training plan. Clear rung definitions belong in the role descriptions too, which the transformer role design guide covers.

DESIGN AND RATING: ______  COIL: LV / HV / tertiary.  CONDUCTOR: size, covering, strands.
FORMER AND MANDREL: which one, packing used, starting position.
TENSION SETTING: brake position that worked, and how the senior judges it by hand.
SEQUENCE: layers or discs, transposition points, where spacers and duct sticks go.
TAPPING LEADS: turns at which leads come out, brazing method, insulation wrap.
CHECKS DURING WINDING: height after each section, turn count method, what to do if height runs over.
KNOWN TRAPS: notes in the master's own words, with phone photos of the tricky points.
WOUND BY: names and dates for every coil of this design, from the traveller.

The card is filled while the master winds, by a junior holding the phone and a notebook. It is far easier than asking a busy master to write a manual, and it records the parts he would never think to mention.

The person who holds the skill has to want to pass it on. Recognition matters as much as money. Give the master a title such as chief winder, a lighter output count while training, a voice in design reviews and credit when a junior signs off. Benchmark pay against nearby works, since competitors know exactly who your master is. The transformer retention page sets out further levers, and succession planning covers naming successors before a leaving date is fixed.

Ask your master winder who is learning from him, and which coil he would trust that person with today. Count units reopened last quarter and which coil caused each. Then start a winding card on the next new design. The transformer manufacturers page lists the trade's other pressure points, and the electrical equipment manufacturing section sets them beside panels, motors and cable.