The torque developed in the squirrel cage induction motor with auto-starter is ____________.

Correct option is A

Given:

The torque developed in a squirrel cage induction motor with auto-starter.

Starting torque (Tst), Full load torque (Tn), Starting current (Ist), Full load current (In), and Full load slip (Sf).

For an auto-transformer starter, K represents the tapping (transformation) ratio.

$$\\[8pt]\textbf{Formula Used:} \\[4pt]\text{For Direct Online Starter:} \\[4pt]\dfrac{T_{st}}{T_n} = \left(\dfrac{I_{st}}{I_n}\right)^2 S_f \\[10pt]\text{For Auto Transformer Starter:} \\[4pt]\dfrac{T_{st}}{T_n} = K^2 \left(\dfrac{I_{st}}{I_n}\right)^2 S_f \\[10pt]\text{Where:} \\[4pt]T_{st} \rightarrow \text{Starting torque} \\[4pt]T_n \rightarrow \text{Full load torque} \\[4pt]I_{st} \rightarrow \text{Starting current} \\[4pt]I_n \rightarrow \text{Full load current} \\[4pt]S_f \rightarrow \text{Full load slip} \\[4pt]K \rightarrow \text{Tapping of transformation ratio}$$

Solution:

The torque developed in a squirrel cage induction motor with an auto-starter is

​$$K^2 \times \text{torque with direct switching}$$​​

as per the formula for the Auto Transformer Starter.

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