1. The resistance of the field coils with copper conductor of a dynamo is 120 Ohms at 25 o C. After working for 6 hours on full load, the resistance of the coil increases to 148 Ohms. Calculate the mean temperature rise of the field coil. Take the temperature coefficient of the conductor material as 0.0042 at 0 o C. 2. The resistance of the field coil of a 400 kW, 230-Volt shunt generator is measured after the machine has been standing for some time in a room temperature of which is 21 o C and is found to be 14.6 Ohms. After the generator has been in operation for three hours, the resistance is again measured and found out to be 18.2 Ohms. Determine (a) average temperature of field coils after 3-hours; (b) temperature rise. 3. A certain copper winding has a resistance of 0.25 Ohm @ a temperature of 18 o C. Calculate the temperature rise in the winding, when after the period of operation the resistance increases to 0.81 Ohm.
1. The resistance of the field coils with copper conductor of a dynamo is 120 Ohms at 25 o C.
After working for 6 hours on full load, the resistance of the coil increases to 148 Ohms.
Calculate the mean temperature rise of the field coil. Take the temperature coefficient of the
conductor material as 0.0042 at 0 o C.
2. The resistance of the field coil of a 400 kW, 230-Volt shunt generator is measured after the
machine has been standing for some time in a room temperature of which is 21 o C and is
found to be 14.6 Ohms. After the generator has been in operation for three hours, the
resistance is again measured and found out to be 18.2 Ohms. Determine (a) average
temperature of field coils after 3-hours; (b) temperature rise.
3. A certain copper winding has a resistance of 0.25 Ohm @ a temperature of 18 o C.
Calculate the temperature rise in the winding, when after the period of operation the
resistance increases to 0.81 Ohm.
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