SSE JE Electrical Engineering 28 Oct 2020 Shift 1 Papers

Question : 138 of 200

Marks: +1, -0

In an Induction motor, what will be the value of slip to get maximum torque under running condition?

Solution:

The expression for Torque produced in the induction motor is

\T={3 × 60}/{2 \π\N_{\s}} × {\s \E_{2}^{2} \R_{2}}/{\R_{2}^{2}+(\s \X_{2})^{2}}

Condition to get maximum torque:

{ \d\T }/{ \d\s } = 0

⇒{ \d }/{ \d\s }({3 ×60}/{2 \π\N _{ \s }} ×{ \sE _{2}^{2} \R _{2}}/{ \R _{2}^{2}+( \sX _{2})^{2}})=0

⇒{ \d }/{ \d\s }({ \sR _{2}}/{ \R _{2}^{2}+ s ^{2} \X _{2}^{2}})=0

⇒{( \R _{2}^{2}+ \s ^{2} \X _{2}^{2}) \R _{2}- \sR _{2}(0+2 \s \X _{2}^{2})}/{( \R _{2}^{2}+ \s ^{2} \X _{2}^{2})^{2}}=0

⇒\R _{2}^{2}- \s ^{2} \X _{2}^{2}=0

⇒\R _{2}= \s \X _{2}

The slip at maximum torque is,

\s=\R_{2} / \X_{2}

Go to Question:

Prev Question

Next Question