The minimum insulation resistance between windings and ground is 0.5 megohms.

The minimum insulation resistance between windings and ground is 0.5 megohms.

• A. 0.5 megohms
• B. 5 megohms
• C. 50 megohms
• D. 0.05 megohms

Answer: (A)

Insulation resistance to ground shows how well the winding is insulated from the chassis or earth. A higher reading means less leakage and better insulation. For this equipment, the minimum acceptable insulation resistance is 0.5 megohms. So a measurement of 0.5 megohms or higher means the winding insulation meets the minimum standard; readings below 0.5 megohms indicate degraded insulation and a need for drying, cleaning, or repair. Values like 5 or 50 megohms are higher than the minimum and are acceptable, while 0.05 megohms is far too low and signals poor insulation.

Insulation resistance to ground shows how well the winding is insulated from the chassis or earth. A higher reading means less leakage and better insulation. For this equipment, the minimum acceptable insulation resistance is 0.5 megohms. So a measurement of 0.5 megohms or higher means the winding insulation meets the minimum standard; readings below 0.5 megohms indicate degraded insulation and a need for drying, cleaning, or repair. Values like 5 or 50 megohms are higher than the minimum and are acceptable, while 0.05 megohms is far too low and signals poor insulation.