AC Motor Sizing Calculator & RFQ Schedule

Technical Engineering Sizing Platform

AC Motor Sizing Calculator & RFQ Schedule

Vendor-neutral electrical parameters, continuous shaft torque, full load amperes (FLA), and metric frame geometry reference.

Drive Topology & Electrical Inputs

General engineering parameters for continuous S1 duty operation.

kW
V AC

Sizing Output & RFQ Schedule

Vendor-neutral technical schedule for sizing estimation and procurement RFQ.

[OK] Parameters within Commercial Standards
Continuous operating parameters fall within standard commercial frame envelopes.
Full Load Current (FLA)
4.7 A
Continuous RMS phase current
Continuous Shaft Torque
14.7 Nm / 10.8 lb-ft
@ 1433 RPM (4-Pole)
Nominal Frame Footprint
Frame 100L
Shaft height: 100 mm
Nominal Efficiency / PF
86.7% / 0.82
Full-load eta and cos phi
Drive Topology 3-Phase Induction (Squirrel Cage)
Mechanical Output 2.20 kW / 2.95 HP
Continuous Shaft Torque 14.7 N.m (10.8 lb.ft)
Rated Voltage & Hookup 380V Star / Y (50 Hz)
Poles / Full Load Speed 4-Pole / 1433 RPM (50 Hz)
Frame Envelope Designation Frame 100L (Metric Geometry)
Enclosure & Mounting IP55 / Foot Mounted (IM B3)

This sizing schedule is provided for preliminary technical estimation and engineering reference only. Calculations do not constitute professional engineering certification or guarantee under specific commercial conditions. Ambient thermal derating, switching harmonics, cable run inductance, and duty cycle require site verification against certified manufacturer data sheets.

⏚ MAIN EARTH GROUND (PE) UTILITY GRID · 380V 50Hz STAR-DELTA STARTER 0 8 AMPERE L1 L2 L3 KM-Y KM-D KT · 3s QF L1 L2 L3 PE PWR LOOP: 3-PH 380V + PE (⏚) Squirrel-Cage Rotor 4-Pole · 1433 RPM @ 50 Hz 3~ INDUCTION MOTOR FRAME 100L · IM B3 2.2 kW · 1433 RPM U1 V1 W1 PE W2 U2 V2 COUPLING GUARD CENTRIFUGAL FAN · AHU LOAD Foot Mounted IM B3 Frame 100L · Shaft H = 100 mm
FULL-LOAD S1 RUNNING
Full-Load CurrentFLA 4.7 A
4.7A RMS
Shaft TorqueTn = 9550·P/n
14.7N·m
Full-Load Speedη 86.7% · cosφ 0.82
1433RPM · 4-Pole
Load Rate (Mechanical Torque Demand)100% Rated
0% NO-LOAD50% PARTIAL100% FLA RATED115% SERVICE FACTOR
Engineering Mechanism & Sizing Principle (IEC / NEMA Standards)

An alternating current (AC) induction motor converts three-phase electrical power into mechanical torque via electromagnetic induction. Synchronous rotational speed is governed by ns = 120f / p, where supply frequency f and pole count p determine magnetic field velocity. The resulting rotor slip generates shaft torque T = (9550 × P) / n. Accurate sizing harmonizes load inertia, continuous thermal capacity, and breakdown torque margins to ensure peak operating efficiency across variable-frequency drive profiles.

Engineering Guide: AC Motor Sizing Calculator Principles & Form Factors

An AC motor sizing calculator provides design engineers, electrical estimators, and plant technicians with mathematical modeling to specify continuous operating currents, mechanical output torques, and nominal frame dimensions for industrial rotating equipment. Matching electromagnetic torque, thermal limits, and stator supply voltage ensures system reliability without unnecessary capital expenditure from motor over-sizing.

1. Typical Continuous Torque Reference by Power Rating (4-Pole Baseline)

Shaft continuous torque (Tn) is inversely proportional to rotor speed. Standard 4-pole machines operating on 50 Hz and 60 Hz grids exhibit characteristic full-load torque envelopes:

Rated Power 50 Hz Speed & Torque 60 Hz Speed & Torque Nominal Metric Frame Typical Applications
0.37 kW (0.50 HP) 1380 RPM • 2.56 N·m (1.89 lb·ft) 1680 RPM • 2.10 N·m (1.55 lb·ft) Frame 71 Small dosing pumps, laboratory blowers
0.75 kW (1.00 HP) 1410 RPM • 5.08 N·m (3.75 lb·ft) 1710 RPM • 4.19 N·m (3.09 lb·ft) Frame 80M Centrifugal transfer pumps, light conveyors
1.50 kW (2.00 HP) 1420 RPM • 10.09 N·m (7.44 lb·ft) 1720 RPM • 8.33 N·m (6.14 lb·ft) Frame 90L Hydraulic power packs, packaging machinery
2.20 kW (3.00 HP) 1430 RPM • 14.69 N·m (10.84 lb·ft) 1730 RPM • 12.14 N·m (8.95 lb·ft) Frame 100L Industrial fans, air handling units (AHU)
4.00 kW (5.50 HP) 1440 RPM • 26.53 N·m (19.57 lb·ft) 1740 RPM • 21.95 N·m (16.19 lb·ft) Frame 112M Centrifugal blowers, vacuum extraction pumps
7.50 kW (10.0 HP) 1450 RPM • 49.40 N·m (36.43 lb·ft) 1750 RPM • 40.93 N·m (30.19 lb·ft) Frame 132M Rotary screw compressors, slurry pumps
15.00 kW (20.0 HP) 1460 RPM • 98.12 N·m (72.37 lb·ft) 1760 RPM • 81.39 N·m (60.03 lb·ft) Frame 160L Heavy screw conveyors, process chillers
30.00 kW (40.0 HP) 1470 RPM • 194.9 N·m (143.8 lb·ft) 1770 RPM • 161.9 N·m (119.4 lb·ft) Frame 200L Crushers, main water utility pumps
55.00 kW (75.0 HP) 1480 RPM • 354.9 N·m (261.8 lb·ft) 1780 RPM • 295.1 N·m (217.6 lb·ft) Frame 250M Extruders, heavy ball mills, cooling tower fans

2. Winding Topologies & Voltage Matching (Delta vs. Star)

Industrial 3-phase asynchronous motors have six external terminals inside the conduit box (designated U1-U2, V1-V2, W1-W2). How these stator phases are bridged determines their continuous voltage rating:

Winding Hookup Mains Supply Voltage Phase Coil Voltage Typical Industrial Application & Sizing Context
220V Delta / 380V Star 3-Phase 220V or 380V 220 V Common in small motors (≤ 3 kW). Connected in Star (Y) for 380V distribution. Connecting in Delta on 380V will over-excite stator coils by 1.732×, leading to immediate thermal failure.
380V Delta / 660V Star 3-Phase 380V or 660V 380 V Standard for medium-to-large motors (≥ 4 kW). Allows Star-Delta (Y-Δ) reduced-voltage starting on 380V networks to limit inrush current during acceleration.
400V Delta / 690V Star 3-Phase 400V or 690V 400 V Standard heavy industrial metric distribution. Operates in Delta on 400V mains and Star on 690V process distribution.
1-Phase PSC (Single Run Cap) 1-Phase 110V / 220V / 230V Mains Voltage Permanent Split Capacitor. High continuous running efficiency with quiet operation, but modest breakaway starting torque (0.5 to 0.8× rated). Ideal for fans and centrifugal pumps.
1-Phase Dual Capacitor 1-Phase 110V / 220V / 230V Mains Voltage Combines electrolytic start capacitor (disconnected via centrifugal switch) and run capacitor. Yields high breakaway torque (2.0 to 2.5× rated) for piston compressors and loaded conveyors.

3. Governing Electromechanical Equations

Motor shaft torque, rotational velocity, and input electrical power balance across air-gap electromagnetic boundaries according to established engineering physics:

Tn =
9550 × PkW nrated
[N·m]   ≡   Tlb·ft =
5252 × PHP nrated
[lb·ft]
Where PkW is shaft mechanical output power in kilowatts, PHP is mechanical horsepower, and nrated is full-load rotational speed in RPM.
nsync =
120 × f p
[RPM],      nrated = nsync × (1 − s)
Where f is grid frequency (50 or 60 Hz), p is stator pole count (2, 4, 6, 8), and s is rotor slip (typically 0.015 to 0.05 for industrial induction machines).
IFLA (3-Phase) =
PkW × 1000 √3 × VLL × cosφ × η
[A],      IFLA (1-Phase) =
PkW × 1000 VLN × cosφ × η
[A]
Where VLL is line-to-line RMS AC voltage, VLN is single-phase supply voltage, cosφ is full-load operating power factor, and η is conversion efficiency according to IEC 60034-30-1.

4. Standard Metric Motor Frame Envelope Reference

General industrial metric motor footprints conform to fixed physical shaft heights and bolt hole patterns, ensuring field interchangeability:

Frame Designation Shaft Center Height (H) Shaft Diameter (D) Shaft Extension Length (E) Typical 4-Pole Power Envelope
Frame 80M 80 mm 19 mm 40 mm 0.75 kW (1.0 HP)
Frame 90S / 90L 90 mm 24 mm 50 mm 1.1 kW – 1.5 kW (1.5 – 2.0 HP)
Frame 100L 100 mm 28 mm 60 mm 2.2 kW – 3.0 kW (3.0 – 4.0 HP)
Frame 112M 112 mm 28 mm 60 mm 4.0 kW (5.5 HP)
Frame 132S / 132M 132 mm 38 mm 80 mm 5.5 kW – 7.5 kW (7.5 – 10 HP)
Frame 160M / 160L 160 mm 42 mm 110 mm 11 kW – 15 kW (15 – 20 HP)
Frame 180M / 180L 180 mm 48 mm 110 mm 18.5 kW – 22 kW (25 – 30 HP)

5. Frequently Asked Questions (FAQ)

When should I specify a dual-capacitor 1-phase motor over a single-capacitor (PSC) unit?
Selection hinges on breakaway starting resistance. Centrifugal pumps and axial fans start unloaded, requiring minimal starting torque; a single-capacitor (PSC) motor is well suited, providing high operational efficiency and low acoustic noise. Conversely, positive displacement compressors, heavily loaded conveyors, and gear pumps require 200% to 250% locked-rotor torque, demanding a dual-capacitor design to prevent stall and capacitor burn-out during start-up.
Why do motors 4 kW and larger typically utilize 380V/660V or 400V/690V dual windings?
This dual-voltage wound stator allows motors to operate in Delta (Δ) under normal 380V or 400V supply, while facilitating Star-Delta (Y-Δ) reduced voltage starting. Starting in Star connects the coils across line-to-neutral potential (√3 lower), reducing locked-rotor current and starting torque to one-third of across-the-line values, minimizing network voltage sags.
Does identical frame sizing guarantee complete field interchangeability?
Standard metric frame designations (such as Frame 100L or 132M) define shaft center height, shaft diameter, keyway dimensions, and mounting foot hole spacing. However, overall axial length, terminal box orientation, and fan cowl clearance can vary between manufacturers. Always verify total envelope clearance in tight machine enclosures.