Calculadora de Dimensionamiento de Motores

Ingresa HP, voltaje y eficiencia del motor para calcular FLA, tamaño de arrancador, protección de sobrecarga y calibre de cable según NEC. Soporta motores monofásicos y trifásicos.

Load Power

Speed (RPM)

Service Factor

Motor Phase

Common Applications

Recommended Motor

Recommended HP

60 HP

44.74 kW

NEMA Frame

364T-365T

Efficiency

95.0%

NEMA Premium

Required HP

57.50 HP

Full-Load Torque

175.1 ft·lb

FLA at 200V

169 A

FLA at 230V

154 A

FLA at 460V

77 A

FLA at 575V

62 A

Motor Nameplate

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What is a Motor Sizing Calculator?

A motor sizing calculator determines the correct motor horsepower (HP), frame size, and electrical requirements for a given mechanical load. It uses NEC (National Electrical Code) tables for full-load amperage, NEMA frame standards for physical dimensions, and motor efficiency data to recommend the right motor. Proper motor sizing prevents undersizing (overheating, premature failure) and oversizing (wasted energy, poor power factor).

How to Use the Motor Sizing Calculator

Select the Motor Sizing tab and enter your mechanical load power in HP or kW
Set the speed (RPM) and service factor for your application (1.15 for general purpose, 1.25 for severe duty)
Choose three-phase or single-phase and view the recommended motor HP, NEMA frame, and FLA at standard voltages
Use the FLA Table tab to look up full-load amps from NEC Table 430.248 (1-phase) or 430.250 (3-phase)
Use the Starter Sizing tab to determine the NEMA starter size, overload relay, and breaker for your selected starting method

Frequently Asked Questions

How do I determine the HP I need for a motor?

Calculate the mechanical power your load requires: HP = (Torque in lb-ft × RPM) / 5252. Then multiply by the service factor (1.15 for normal duty, 1.25 for severe duty) and round up to the next standard motor size. This calculator automates this process — enter your load power and service factor, and it recommends the correct NEMA standard motor size.

What is the difference between NEC Table 430.248 and 430.250?

NEC Table 430.248 provides full-load current (FLA) for single-phase AC motors at 115V, 200V, and 230V. Table 430.250 covers three-phase AC motors at 200V, 230V, 460V, and 575V. These tables are used for sizing conductors, overload protection, and short-circuit protection — not the motor nameplate FLA, which may differ.

What NEMA frame size do I need?

NEMA frame size is determined by motor HP and speed. For standard 4-pole (1800 RPM) motors: 1-2 HP use 143T-184T frames, 3-5 HP use 182T-184T, 7.5-10 HP use 213T-215T, 15-20 HP use 254T-256T, up to 200 HP using 447T-449T frames. The frame determines mounting dimensions, shaft height, and shaft diameter.

What is the difference between DOL, Star-Delta, Soft Starter, and VFD?

DOL (Direct On Line) applies full voltage instantly — simple but draws 6-8× FLA inrush. Star-Delta starts at reduced voltage then switches — 2-3× FLA inrush. Soft starters ramp voltage gradually — 3-4× FLA. VFDs control frequency and voltage for the smoothest start at 1-1.5× FLA, plus speed control benefits.

How do I size a motor starter per NEC?

Motor starters are sized by NEMA standards based on motor HP and voltage. The overload relay is set to 115-125% of motor nameplate FLA. Branch circuit breakers follow NEC 430.52: 250% FLA for inverse-time breakers (DOL), or 150% for VFD applications. The starter contactor must be rated for the motor HP at the system voltage.