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Motor Sizing

T = J·α, with α from the speed change over the accel time. A gearbox reflects load inertia by 1/ratio² and divides load torque by the ratio — which is why gearing helps inertia mismatch so much. P = T·ω.

Calculator

Load inertia J (kg·m²)

Motor inertia (kg·m²)

Gear ratio

Speed change (rpm)

Accel time (s)

Load torque (N·m)

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Reflected inertia

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Angular accel

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Accel torque

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Load torque (at motor)

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Required power

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Power (kW)

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Add friction, duty cycle and a service factor before selecting. A helper, not a substitute for engineering judgment.