Which of the following materials is used in the manufacture of resistance grids to be used in the starters of large motors ?
Correct answer: D. Cast-iron
- A. Copper
- B. Aluminium
- C. Steel
- D. Cast-iron
Explanation
Cast iron is used for starter resistance grids because its relatively high resistivity allows compact resistance and its high heat capacity tolerates starting heat pulses. Copper and aluminium have too little resistance for this purpose.
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