The Principle Of Dry Type Transformer

1. Working Principle: Electromagnetic Induction

(1) Core Process

1. When the primary winding is connected to an AC power supply, alternating current (I₁) flows through it, generating alternating magnetic flux in the closed iron core.
2. According to the electromagnetic induction law, this alternating magnetic flux passes through both the primary and secondary windings, inducing an electromotive force (voltage) in the secondary winding.
3. When the secondary winding is connected to a load, the induced electromotive force drives load current (I₂), realizing energy transfer from the primary to the secondary.

(2) Voltage & Current Transformation

• The voltage ratio is determined by the number of turns of the primary (N₁) and secondary (N₂) windings: U₁/U₂ = N₁/N₂.
• The current ratio is inversely proportional to the turn ratio: I₁/I₂ = N₂/N₁ (to maintain power balance, ignoring losses).
• Transformer Type Definition:
  • If U₁ > U₂ (N₁ > N₂): Step-down transformer (most common, e.g., 10kV/0.4kV for distribution).
  • If U₁ < U₂ (N₁ < N₂): Step-up transformer (used for long-distance power transmission).

(3) Key Advantage of Cast Coil Design

2. Installation Environment Requirements (Epoxy Resin Dry-Type Transformers)

(1) IP Protection Rating Constraint

• Indoor Use (Standard): Equipped with IP20 protection rating as default. It prevents intrusion of solid foreign objects ≥12.5mm (e.g., fingers, large debris) and withstands dripping water at a 15° angle—suitable for dry, clean indoor power distribution rooms.
• Outdoor Use (Special Requirement): Must be upgraded to IP23 protection rating (adds rainproof and dustproof capabilities). Without IP23, it cannot be used outdoors (moisture and dust will damage epoxy insulation).

(2) Ventilation Requirement

• The installation environment must have good natural or forced ventilation. The air flow rate around the transformer should be ≥0.5 m/s to ensure heat dissipation (avoiding overheating caused by poor air circulation).
• Keep a distance of ≥0.6m from walls or other equipment to reserve ventilation space.

(3) Cleanliness & Anti-Contamination

• The environment must be clean, free of excessive dust, corrosive gases (e.g., sulfur dioxide), or conductive particles (e.g., metal shavings). These contaminants will adhere to the coil surface, reducing insulation resistance and causing partial discharge.

(4) Anti-Animal Intrusion

• Install anti-rodent (rats, mice) and anti-snake devices around the transformer. Rodents or snakes entering the equipment may gnaw wires or cause short circuits between windings.

3. Protective Devices & Materials

(1) Protective Cover (Enclosure)

• Material: Made of steel, aluminum alloy, or stainless steel—corrosion-resistant, durable, and mechanically strong.
• Core Functions:
  • Achieve the required IP protection rating (e.g., IP20 for indoor enclosures with mesh ventilation holes; IP23 for outdoor enclosures with sealed panels and waterproof joints).
  • Prevent physical damage to coils and bushings during transportation or operation.

(2) Supplementary Protection

• For dusty environments (e.g., workshops), add a detachable dust filter to the enclosure’s ventilation holes—regularly clean the filter to maintain airflow.
• For high-humidity areas (e.g., coastal regions), the enclosure can be painted with anti-corrosion coating (e.g., epoxy primer + polyurethane topcoat) to extend service life.