What is need of motor starter or advantages of motor starter ?
Answers
Answered by
0
In a small motor usually the current requirement is small. So the armature resistance is high. The rotor in the motor may not spin at high speeds. Here the current flowing the armature is small and so does not create any trouble.
But in huge motors of 3-phases. the load and power requirements are high. The armature resistance is low, for example, a few Ohms only, in order to have higher efficiency. The normal current flowing in the armature is around 10 A to 60 Amp for example.
When the motor is connected across 220V or 440 V supply, the the current that flows immediately will be in hundreds of Amperes. That could be more than 3 times rated current. That will damage the motor parts and burn the armature coil itself.
However, when the motor is running at full speed, there is a back emf that is generated which depends on the armature wire length, speed of rotation and the magnetic field of the permanent magnets. This emf is generated to oppose the current that induces the rotation of the rotor. This is according to the Faraday's law of Induction.
This back emf opposes the input voltage to the motor and reduces the net potential drop across the coil. However, back emf is substantial only when the motor rotates at full speed.
In order to fix this problem, a motor starter is used. Motor starter has a high resistance. At the time of starting of the motor, motor starter is connected in the circuit. So motor rotates slowly and develops the back emf. Slowly the motor reaches its full speed and then either manually or automatically the motor starter is disconnected.
motor starter advantage: It protects the motor and armature against high initial current.
It disconnects later so the dissipation of heat is avoided. So efficiency is improved.
But in huge motors of 3-phases. the load and power requirements are high. The armature resistance is low, for example, a few Ohms only, in order to have higher efficiency. The normal current flowing in the armature is around 10 A to 60 Amp for example.
When the motor is connected across 220V or 440 V supply, the the current that flows immediately will be in hundreds of Amperes. That could be more than 3 times rated current. That will damage the motor parts and burn the armature coil itself.
However, when the motor is running at full speed, there is a back emf that is generated which depends on the armature wire length, speed of rotation and the magnetic field of the permanent magnets. This emf is generated to oppose the current that induces the rotation of the rotor. This is according to the Faraday's law of Induction.
This back emf opposes the input voltage to the motor and reduces the net potential drop across the coil. However, back emf is substantial only when the motor rotates at full speed.
In order to fix this problem, a motor starter is used. Motor starter has a high resistance. At the time of starting of the motor, motor starter is connected in the circuit. So motor rotates slowly and develops the back emf. Slowly the motor reaches its full speed and then either manually or automatically the motor starter is disconnected.
motor starter advantage: It protects the motor and armature against high initial current.
It disconnects later so the dissipation of heat is avoided. So efficiency is improved.
Answered by
6
Answer:
Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to themotor, which is connected in series to the motor's armature winding and restricts the current to an acceptable level.
Similar questions