Popular Knowledge of Transformers

I. What is a transformer?

Core function: through the principle of electromagnetic induction to change the alternating current voltage (step-up / step-down)

Energy conversion: electrical energy → magnetic energy → electrical energy (conservation of energy, output power ≈ input power)

Symbol: circuit diagram with two coils + vertical line in the center (⚡️→⚡️)

Key point: transformers can only change AC voltage, not effective for DC!

Second, the principle of operation: electromagnetic induction

The primary coil is energized with alternating current → alternating magnetic field is generated.

The magnetic field passes through the iron core → the secondary coil cuts the magnetic lines of inductance → induced voltage

Voltage transformation formula:

V₂ / V₁ = N₂ / N₁

(V = voltage, N = number of turns in the coil, the subscript 1/2 stands for primary/secondary respectively)

Example:

Step-down transformer: input 220V (N₁ = 1000 turns) → output 12V (N₂ = 55 turns)

Step-up transformer: wind turbine output 690V → step-up to 10kV into the grid

Anatomy of the core structure

Components: Materials and Roles

Core: Silicon steel sheet stacked (to reduce eddy current losses), to provide a magnetic pathway

Coil: Copper/aluminum wire winding, primary to power supply, secondary to load

Insulating oil: mineral oil or synthetic ester (cooling + insulation), large transformers need to be oil-immersed to prevent breakdowns

Heat sink: corrugated oil tank/heat sink (to prevent overheating)

Tap changer: adjustment of the number of turns of the coil (±5% voltage fine-tuning)

Cold knowledge: transformer hum is generated by vibration of silicon steel sheet under 50Hz magnetic field!

IV. Classification and Application Scenarios

Type Feature and use

Power transformer Power grid hub (500kV ultra-high voltage transmission → 10kV distribution → 220V to the home)

Distribution transformer Small area/factory terminal voltage reduction (column/box type)

Instrument Transformer Transformer (CT/PT) to convert high voltage/high current to safe measurement value

Electronic transformer Cell phone charger (220V→5V), audio equipment isolation interference

Special transformer Arc furnace transformer (super high current), rectifier transformer (electrolytic aluminum)

V. Key performance parameters

Rated capacity: unit kVA (example: neighborhood distribution transformer common 630kVA)

Efficiency: 95%-99.7% (large transformer loss <0.3%)

Cooling method:

ONAN (oil-immersed self-cooling)

OFAF (forced oil circulation air-cooled)

Insulation level: A (105 ℃) to H (180 ℃), determine the temperature resistance ability

Six, cutting-edge technology breakthroughs

Superconducting Transformer

Bismuth-based superconducting coils cooled by liquid nitrogen instead of copper wires → zero resistance, 90% loss reduction

Challenge: high cost of cryogenic system (Siemens 420kV prototype tested)

Amorphous alloy core

Atomic disorder → magnetization losses 70% lower than silicon steel

Application: State Grid Rural Transformation Project (annual power saving of 2 billion kWh)

Smart Transformers

Integrated power electronics + AI algorithm → automatic voltage regulation, fault prediction

VII. Safety and Energy Saving General Knowledge

Hazard warning:

⚠️ Breakage of insulation on the high voltage side may cause an arc explosion (temperatures exceeding the surface of the sun!)

⚠️ Waste transformer oil contains carcinogens and requires professional treatment.

Power saving tips:

✅ Choose first-class energy efficiency (e.g. SCB18 dry-type transformer).

✅ Avoid long-term low load operation of the transformer (efficiency degradation)

Eight, interesting cold knowledge

The world's largest transformer: China Kunliulong DC project ± 800kV converter (weighing 700 tons ≈ 500 cars)

The earliest transformer: 1885, Hungary, Gantz factory manufacturing (5kVA, efficiency of only 80%)

Voltage “pacemaker”: on-load voltage regulator switch adjusts voltage without disconnecting the power supply

Thinking question: Why use step-up transformers for high-voltage power transmission?

Answer: Reduce current → reduce line losses (P loss = I²R), higher voltage is more economical for the same power!