Motor Selection Std
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▸Formula · assumptions · example(IEC 60034-1 / IEC 60034-30-1 (IE3/IE4 Premium Efficiency) · NEMA MG-1)
Formula
P_{\text{req}} = \frac{T_{\text{load}} \cdot \omega}{1000 \cdot \eta_{\text{trans}}}, \quad T_{\text{acc}} = (J_{\text{motor}} + J_{\text{load}}') \cdot \alpha, \quad P_{\text{installed}} \ge P_{\text{req}} \cdot k_{\text{service}}
IEC 60034 three-phase induction and servo motor sizing, reflected load inertia ratio J_load/J_motor, and thermal continuous torque margin.
Assumptions
- · Reflected inertia ratio to motor shaft (J_load/J_motor) designed within stable control range (≤ 5:1 for dynamic servo, ≤ 10:1 for standard drives)
- · Ambient operating temperature ≤ 40 °C at installation altitude ≤ 1000 m above sea level
- · Service factor k_service chosen per daily duty cycle and shock loading class (A/B/C)
Worked example
Worked example — Conveyor Drive (Tload = 45 N·m, speed n = 150 rpm, reducer η = 0.90, service factor = 1.25)
Net mechanical power Pnet = 0.707 kW. Accounting for reducer efficiency and service factor yields 0.98 kW, sizing a standard IEC 90S 1.1 kW 4-pole IE3 motor.