Answer / harish

depends which component rheostat..if field rheostat is
there it should be at the minimum....the armature rheostat
should be at the maximum..it should be done to limit the
speed of the machine.....at starting due to very less
induced emf the speed increases terribly

Answer / bhavani

In dc motor v=Eb-IaRa is the voltage equation.at starting Eb=0 so V=IaRa and the armature resistance is very small nearly 0.01ohm.so Ia increases ,to avoid this problem we kept 3-point starter.in motors field resistance is kept in minimum in order to get high starting torque.if v increases speed also increase and flux in field rheostat and field current are decreases. at the instant of starting to control the speed not to go beyond its rated value.that's why we kept field resistance in minimum.If we kept in maximum,R increases,I decreases,N increases so the motor will exceed its rated speed,then motor will damaged.or to avoid this probiem,we can control the speed of motor ,when armature rheostat is in maximum,voltage applied is minimum,so N decreases.so we will get rated speed by controlling any one of this.either by incresing applied voltage to armature or by decreasing the current in field winding.THANK YOU

Answer / karthik raman.b

N indirectly proportional to the field flux if it is o the speed will be dangerous so we have to keep in minimum position

Answer / ramanareddy

actually rheostat means -diverting......if keep the rheostat in minimum position motor will run at rated speed....if rheostat in maximum position ,the motor will run above the rated speed ,so that speed make the motor damage....

Answer / habeebm

The speed of the motor will reduce.

Answer / therion

i rheostat is just a potentiometer so speed will slow to
minimum or speed up to maximum

Answer / jyothi

if resistance is low then flux high,if then speed is low
because N invrsely praportional to flux

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