00:01
Hello, in the question we have given that a 230 v dc shunt motor, so we have given the voltage, so that is equal to 230 v and this is dc shunt motor has an armature resistance of 0 .5 ohms.
00:20
So, this armature resistance we will call it as ra that is given to be 0 .5 ohms and r shunt, so we have given the shunt resistance, so r shunt is equal to 115 ohms.
00:39
So, at no load the speed is 1200 rpm, so we will call this as n1, so that is 1200 rpm and the armature current is ia, so i will write over here, so armature current is 2 .5 amperes.
01:02
Further, on application of the rated load, speed drops to 1120 rpm, so n2 is 1120 rpm, rotations, revolutions per minute.
01:18
So, determine line current and the power input when motor delivers rated load.
01:26
So, now these are the known quantities, so we will simply use the equation over here, so that is emf is equal to e minus ia ra.
01:41
So, if we plug the values, so we know what it is, so we have given this voltage to be 230 minus ia, the armature current is given that is of 2 .5 amperes into ra is 0 .5, let us check, it is 0 .5.
02:05
So, from here if we calculate this emf, so we will get it as 228 .75 volts.
02:19
So, now this emf, this is the emf, so now this emf we can use to find out the emf across the load.
02:35
So, we can use e1 by e2 is equal to n1 by n2 because e is directly proportional to n.
02:44
So, from that, so we know what is e1, we just calculated, so we will call this over here as e1.
02:55
So, e2 from here will be equal to n2 divided by n1 times e1.
03:01
So, let us plug the value, so n2 is 1120 divided by 1200 times 228 .75.
03:15
So, if we calculate this, we will get this e2 as equals to 213 .5 volts.
03:27
So, now again we will use this equation e is equals to v minus i times r, so it will be ia ra.
03:42
So, from here i can find out this current.
03:45
So, this current will be equal to, so this will be, so i will bring over here, so this will be v minus e divided by ra.
03:57
So, this is 230 minus e is 213 .5 divided by 0 .5.
04:11
So, from here, if we calculate, we will get this i as equals to 33 amperes, but this is not the line current, this is the armature current...