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Question Detail
Belt conveyors offer
Options
Option A: Zero starting torque
Option B: Low starting torque
Option C: Medium starting torque
Option D: High starting torque
Correct Answer
High starting torque
Solution & Explanation
{"type":"technical","methodBadge":"Concept & Principle","explanation":"Belt conveyors are high-inertia, constant-torque loads that require significant force to overcome static friction and inertia at the instant of starting. Therefore, electric motors driving these conveyors must possess a high starting torque characteristic to initiate movement from a standstill.","workingPrinciple":"The total torque required for a conveyor is given by $T_{total} = T_{static} + T_{inertia}$, where $T_{static}$ accounts for the friction of rollers, belt weight, and material load, and $T_{inertia}$ is $J \\cdot \\frac{d\\omega}{dt}$. During start-up, the motor must overcome the combined static friction (which is higher than dynamic friction) and accelerate the entire mass of the conveyor system, necessitating a torque significantly higher than the running torque.","diagramSvg":"Conveyor Torque RequirementStatic Friction + InertiaHigh Starting Torque Required","keyFormulas":["$T_{start} > T_{static} + J \\cdot \\frac{d\\omega}{dt}$ тАФ Requirement for motor torque at start","$T \\propto \\Phi \\cdot I_a$ тАФ Torque production in DC motors"],"keyPoints":["Conveyor systems belong to the 'Constant Torque' load category.","The starting period is critical for protecting the belt and motor from overcurrent.","DC Series motors or Slip-ring Induction motors are often chosen for such applications due to their high starting torque capability."],"advantages":["Ensures smooth acceleration of heavy loads","Prevents motor stalling during initial phase"],"disadvantages":["High current draw during startup","Mechanical stress on belt splices and drive components"],"applications":["Mining and mineral processing","Bulk material handling systems","Heavy industrial manufacturing"],"comparisonTable":[],"additionalInfo":["Low starting torque motors would fail to move a loaded belt conveyor, leading to locked-rotor current and potential motor burnout.","Option A is incorrect because zero torque would mean no motion; options B and C are insufficient for the heavy breakaway forces involved."],"answer":"D is correct тАФ Belt conveyors are high-inertia loads that require high starting torque to overcome static friction and initiate motion.","correctedOptions":["Zero starting torque","Low starting torque","Medium starting torque","High starting torque"],"coreConcepts":["Starting Torque","Inertia Loads","Conveyor Dynamics"],"crossTopicTip":"For high-inertia loads like conveyors and crushers, always choose motors with high starting torque (e.g., DC Series or Wound-rotor Induction motors). In speed control, variable frequency drives (VFDs) are now preferred as they provide high torque at low speeds."}
