Direct Current machines lectures.pptx

DC Machines

1. DC MACHINES

2. A linear DC machine comprises of battery with a resistor linked with each in the use of a switch that makes frictionless rails. The expression of the force applying on the wire in the existence of magnetic field is F = i (I X B) Here F denotes the force applying on wire, i is the magnitude of current flowing in wire, I is the length of wire, B is the magnetic flux density

3. The expression of the voltage produced in the moving conductive wire is in the field is e ind = ( vXB ) . l e ind denotes voltage in the wire v denotes the velocity of the wire B indicates magnetic flux density I is the length of the conductor

4. If we apply KVL to the circuit shown in the above figure V B – iR – e ind = 0 V B = iR + e ind When the switch is closed i = ( V B - e ind )/R

5. Starting Linear DC Machine When the switch is closed i = ( V B - e ind )/R As the bar is at rest e ind or induced voltage value is zero. In a result above equation become i =V B /R F is induced F = ilB to the right When the velocity of bar increases e ind = vBl in up direction Which reduces the current to The induced force is decreased till it becomes zero. At this point e ind = V B and the bar moves at constant no load speed

6. ROTATING LOOP BETWEEN CURVED POLE FACES