Dc Machine :: essays research papers

2a.i) Startup of a linear DC machineStartup of a linear DC machine (See figure 1.1)1.The switch is closed which allows current to flow. The current flows survey the prohibition, which is given Kirhhoffs electromotive crush law.Note The band was at remnant so eind = 0 I = VB-eind = VB/R R R2. bandage this current flows thu the there is a magnetic suck up, which induce a force on the wires. become = i/B3. The bar leave accelerate. When the the hurrying of the bar annex, the voltage appears across the barfind = vBl4. Thus the adjoin voltage reduces the current flowing through the bar.I = VB-eind R5. The egress of this action is that eventually the bar will reach a immutable steady state speed where the net force on the bar is zero. This happen when eind has risen all the way up to equal the voltage of VB & I=0. At that time the bar will be mournful at a speed given byVss= VB Bl6. The bar will continue to move forever unless some external force disturbs it. running(a) DC Motor or Generatorii) Motor Operation (See Fig 1.2)Since the bar was initially at steady state, application of the force Fload proceeding will result in a force on the bar in the direction opposite the direction of consummation.Fnet = Fload Find The resulting acceleration a = Fed/m is negative, so the bar slows down the voltage eind=v Bl falls, and so I=(VB eind)/R increaseThe induced force Find = I lB increase until Find = Fload at a lower speed v.An amount of electrical power equal to eindi is now world converted to mechanical power equal to Findv and and the machine is acting as a motoriii) Generator Operation (See Fig 1.2)The concept of a generator is similar to the motor. When (Fig 1.2) moved rapidly it is a generator precisely when it move slowly it a motor. In a Generator a force is applied in direction of motion. Now the applied force will cause the bar to accelerate in the direction of motion and the velocity of the bar will increase as the velocity increase , eind = v Bl will increase and will be larger than the bombing voltage VB.