A series-wound commutator motor has the best starting torque because the torque is proportional to the square of the current, and the starting current is set by a current-limiting resistor which is switched out as the motor builds up speed.
Ac motor has a low starting torque so that DC series motor used in railways cause DC motor has high starting torque
capacitor start motor
With some motor designs, as the motor starts to accelerate, its torque tends to fall somewhat before starting to increase again. The point of lowest torque in this region of the curve is termed the 'pull-up torque'.
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to obtain high starting torque
The torque which is produced during the starting of motor is simply called as starting torque.
1. Induction motor has high starting torque, therefore use for operate pump which need high starting torque. 2. Induction motor operate on variable speed. 3. It can be used as generator when speed of motor is higher than synchronous speed.
DC motors can spin at a much faster speed and have higher starting torque.
Ac motor has a low starting torque so that DC series motor used in railways cause DC motor has high starting torque
capacitor start motor
YES
The starting torque is low because this type of motor requires an additional way of ensuring that it starts rotating the right way. It is not economical to give this additional mechanism the capacity to deliver the full load torque.
With some motor designs, as the motor starts to accelerate, its torque tends to fall somewhat before starting to increase again. The point of lowest torque in this region of the curve is termed the 'pull-up torque'.
If the starting torque required is too high for a shunt motor, it could lead to stalling or jerky operation at startup. This can cause overheating and damage to the motor windings due to increased current draw. It is important to match the motor's torque capabilities with the load requirements to prevent these issues.
While starting a motor from standstill to its rated speed, the motor has to overcome the inertia and generate enough torque to over come it. In the process the motor takes higher current during the starting. Once started and set in motion the current reduces ti its normal value. Full load current is lower than the starting current normally.
Sometimes, for example in a separately excited dc motor. But in a series-wound dc motor the torque is proportional to current-squared, which gives the motor a very high starting torque and this makes series motors very popular for traction.
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