With reference to Dry-type Transformers in commercial buildings, consider the following:1.They use air as the cooling and insulating medium instead of oil.2.They are preferred for indoor installations due to reduced fire hazard.3.They require frequent oil filtration and acidity testing.Which of the statements given above is/are correct?

Correct Answer: A - 1 and 2 only

Quick Concept Explanation

Dry-type transformers use solid insulation and air/natural/forced-air cooling rather than flammable insulating oil. Their lower fire and environmental risk makes them suitable for indoor/commercial installations. Key relation: Cooling classes include AN/AF for dry-type designs.

Exam focus: Indoor fire-risk questions often favor dry-type transformers. Common trap: Oil maintenance belongs to oil-filled transformers, not dry-type units.

Statement-wise Verification

• Statement 1 - Correct.
  They use air as the cooling and insulating medium instead of oil.
  Dry-type transformers use solid insulation and air/natural/forced-air cooling rather than flammable insulating oil.
• Statement 2 - Correct.
  They are preferred for indoor installations due to reduced fire hazard.
  Their lower fire and environmental risk makes them suitable for indoor/commercial installations.
• Statement 3 - Incorrect.
  They require frequent oil filtration and acidity testing.
  Dry-type transformers do not contain insulating oil, so routine oil filtration/acidity testing is inapplicable

Core Concept

Dry-type transformers use solid insulation and air/natural/forced-air cooling rather than flammable insulating oil. Their lower fire and environmental risk makes them suitable for indoor/commercial installations. Because there is no transformer oil, oil filtration and acidity testing are not routine requirements.

Formula / Key Relationship

Cooling classes include AN/AF for dry-type designs.

Why the Other Options Are Wrong

Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1. Option C is incorrect because it omits correct statement(s) 2. Option D is incorrect because it includes incorrect statement(s) 3.

Exam Shortcut / Approach

Indoor fire-risk questions often favor dry-type transformers.

Common Mistake

Oil maintenance belongs to oil-filled transformers, not dry-type units.

Quick Revision

Indoor Fire Safety and Cooling is linked with Dry-Type Transformer, Transformers and Electrical Building Services. Indoor fire-risk questions often favor dry-type transformers.