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Which of the following Drying out method is note used in rotating machines?
Incandention lamp
Heating chamber
Circulating current
Circulating Oil
Circulating Oil
Quick Summary: Drying out is a maintenance process to remove moisture from electrical machine windings after exposure to damp environments or prolonged storage. 'Circulating Oil' is a cooling and insulation medium used in power transformers, not a method for drying out the windings of rotating electrical machines like motors or generators.
Drying out is a maintenance process to remove moisture from electrical machine windings after exposure to damp environments or prolonged storage. 'Circulating Oil' is a cooling and insulation medium used in power transformers, not a method for drying out the windings of rotating electrical machines like motors or generators.
P=I2R тАФ Power dissipation used in current-based drying
Q=mc╬ФT тАФ Heat energy required to increase temperature
The principle involves raising the temperature of the insulation system above the ambient temperature to drive off moisture. Common methods include passing a low-voltage DC or AC current through the windings (Circulating current), placing the machine in a heating enclosure (Heating chamber), or applying external heat sources such as Incandescent lamps.
Moisture in insulation reduces dielectric strength significantly.
Insulation resistance must be measured periodically during the drying process.
Temperature must be controlled to prevent damage to the varnish or insulation material.
Circulating oil is used for transformer cooling and insulation, not machine drying.
Prevents internal arcing and insulation breakdown
Restores original dielectric properties of the winding insulation
Time-consuming process requiring careful monitoring
Risk of insulation damage if temperature is not regulated
Post-flood restoration of machines
Pre-commissioning of machines stored in high-humidity areas
Standard drying temperature for Class B insulation is typically limited to 90-100┬░C.
Option D is incorrect because oil-filled cooling is a design feature of static equipment, not a drying technique for rotating machines.
D is correct тАФ Circulating Oil is a cooling medium for transformers and is not an accepted method for drying out rotating electrical machines.
Always distinguish between maintenance for static transformers (which use oil) and rotating electrical machines (which rely on air/hydrogen cooling and ohmic heating).