capacitor start motor
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
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'.
4 times
to obtain high starting torque
The torque which is produced during the starting of motor is simply called as starting torque.
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.
A shunt-wound DC motor can maintain its speed well when the load torque varies.
Ac motor has a low starting torque so that DC series motor used in railways cause DC motor has high starting torque
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'.
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.
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.
4 times
to obtain high starting torque
3 Phase induction motor because it produce high torque at starting