What is Saturation in terms of magnetism?
The state when the applied external magnetic field on the material can not increase further causes a peak of magnetization. This peak causes the material to saturate or in terms of the magnetic core to heat up. In Electrical motors, this is severe as if the magnetic core and windings saturate, there will be damage to the electrical components.
A chopper is used to control the speed of a 200-V, 600-rpm, 100-A separately excited DC motor. The motor has an armature resistance of 0.1 Ω. The chopper supply voltage is 200 V and the chopper switching frequency is 1 kHz. What is the motor speed if the motor operates at 50% of the rated torque and the chopper operates at a duty ratio of 0.6? The motor current is assumed continuous. The field current remains constant at rated value.
Ea=Vt-RaIa = 200-100x0.1 =190V Vt=D*V=0.6 x 200 =120V Becasue torque is proportional to Amarture current Ea=Vt-(Ra*0.5*Ia) = 120 - 0.1 x 0.5 x 100 = 115 V n = Ea/Ea(rated) = 115/190 *600 = 363 rpm