Hello friends in this video we are going to see types of DC motor as for the excitation given to the field winding types of DC motor can be classified into two types first is separately excited and second second type is self excited now what do you mean by separately excited we have independent supply for field winding or you can say a separate Supply to field winding to produce a main flux whereas self excited supply for field winding is obtained from arure voltage in self exided depends upon connection of field winding we are having further two different classes one is series motor and second shunt motor series motor field winding is in series with Armature or you can say Armature winding whereas in Shar motor field winding is connected in parallel with arat winding now let's see all these motors one by one first separately excited here field winding is excited through a separate Supply to produce a flux which is responsible for a motoring action this is the Armature excited by Armature voltage or Supply voltage vs it will pass arure current which will generate a bad EMF because of generating action of a motor so these are the terminals F1 F of field winding for Armature A1 and A2 so let's write voltage and current relationship for this since if is independent of vs and any other part of the Armature so constant flux you will get it's a constant F motor because flux only depends on VF so if I apply K to the Armature side I will get vs equal to e + I a v brush e is a b MF I is arat voltage drop and V brush is a drop because of brush resistances we can neglect them so neglecting brush voltage I can say vs = to e + i a r a let's go to Second type that is shun motor in sh motor the field winding is in parallel with the Armature this is Supply voltage vs this is the Armature which will produce a back EMF of this polarity and this is the resistance of field winding since it is connected in shun I will represent it as rsh this will be the arit current I a and this will be the field current if AR ter are A1 A2 field terminals are F1 fub now if I keep vs constant I will get voltage and current equations that we need to list out here I have is nothing but V d s upon RS and EMF equation will be V = to EB + i a r plus v brush now the lower current will be like this applying Cas over here I can get I = to I a + if so these are the voltage and current relationships we are having in a shun motor one important thing if I keep vs constant which is the case most of the time then I will get constant if and the constant if will produce constant flux so flux produce in this this motor is directly proportional to if and if is constant because vs is kept constant this motor is also called as constant flux motor let's move to the third type that is series motor in this motor field winding is connected in series with the Armature this is this is a supply voltage vs this is a resistance of fuel winding since it is connected in series I will represent it as RSC this is a Armature giving a back EMF EB and this will be the load current I let's write voltage and current relation now I is a current taken from the supply that is same as ISC which is same as I a current flowing through this winding is I and through Armature it is I so it's nothing but a same current which is drawn from the supply voltage equation once again it will be vs = to e+ i a r a this time one more drop will come because field winding is in series and that is I a RSA plus v brush so ultimately it is vs = to EB + I is taken common in braet ra a + r c plus v brush now series motor Armature current is passing through the field winding hence flux produce is directly proportional to I which is nothing but a field current or it is directly proportional to arat the current I8 thank you