STARTING
• In the dc motors, at the instant of starting, the back emf Eb = 0 and armature resistance is very less.
• Therefore if rated normal voltage is applied to the armature terminals of the motor the starting current would be dangerously high.
• This high current produces high mechanical stress and also heating which may damage the winding.
• Moreover there would be large voltage drop in the supply line and this affects the other machines working in the same supply line.
• Therefore to limit the starting current to a safe value reduced voltage should be applied to the motor at the time of starting until it picks up speed and develop sufficient back emf.
• Then full normal rated voltage could be applied to bring the motor to the rated speed.
• This could be achieved using starters.
APPLICATIONS
• In the dc motors, at the instant of starting, the back emf Eb = 0 and armature resistance is very less.
• Therefore if rated normal voltage is applied to the armature terminals of the motor the starting current would be dangerously high.
• This high current produces high mechanical stress and also heating which may damage the winding.
• Moreover there would be large voltage drop in the supply line and this affects the other machines working in the same supply line.
• Therefore to limit the starting current to a safe value reduced voltage should be applied to the motor at the time of starting until it picks up speed and develop sufficient back emf.
• Then full normal rated voltage could be applied to bring the motor to the rated speed.
• This could be achieved using starters.
APPLICATIONS
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