NEMA MG-1 / IEEE 841 reference tool — frame sizing, speed, and DOL / VFD datasheet generator
LOW VOLTAGE · ≤ 1000 V · AC INDUCTION
Application Inputs
NEMA
IEC
3-Phase
1-Phase
60 Hz
50 Hz
Supported range: 1–500 HP (0.75–373 kW)
Single-phase range: 1/20–10 HP standard (smallest standard sizes are NEMA 42/48 frame, ~1/20–1/6 HP), up to 15 HP for specialized "farm duty" or crop-drying designs.
Enter a speed to auto-select the nearest pole count instead.
Computed Selection
Synchronous Speed
–rpm
Est. Full-Load Speed
–rpm
NEMA Frame
–
Est. Full-Load Current
–A
Est. Locked-Rotor Current
–A
Assumed Eff. / PF
–
Shaft Diameter (DE)
–
Est. Motor Weight
–
Frame assignment for 1–250 HP at 2/4/6/8 poles uses a published NEMA T-frame assignment
chart (by HP, pole count, and ODP/TEFC) rather than an approximation; larger HP, 10/12-pole,
and 50 Hz cases fall back to a proportional estimate. Below 1 HP, the tool assigns the
standard fractional NEMA frame (42, 48, or 56 — confirmed shaft heights of 2-5/8", 3", and
3-1/2" respectively); single-phase motors stay in the 56 frame up to ~3 HP before stepping to
T-frames, matching common practice, but exact HP breakpoints for these fractional frames vary
more by manufacturer than the integral-HP T-frame chart does. Shaft diameter and center height
follow the published NEMA U/D dimension standard for the resulting frame, so they're normally
reliable. Efficiency/PF and motor weight are typical planning estimates by HP band/frame — not
a specific catalog motor — since weight varies with manufacturer, poles, and enclosure. Always
confirm final frame, shaft, weight, FLA, and LRA against the selected manufacturer's published
data before purchase or panel design.
Hazardous (Classified) Area
Max motor surface temperature must stay below the ignition temperature of the specific gas/dust present, at rated load including any VFD harmonic heating.
Mounting & Mechanical Configuration
F1/F2 describe which side the box sits on when facing the drive end — not the cable exit direction. Bottom-mounted boxes aren't offered here as they're not suitable for horizontal pedestal (foot-mounted) motors.
Direction the conduit/cable knockout faces on the terminal box itself.
Belt and chain drives impose radial (side-pull) shaft loads — confirm bearing L10 life and shaft/bearing rating with the manufacturer for the actual sheave/sprocket pitch diameter and tension.
Motor Outline sketch
Current Selection (Foot Mounted)
C-Face (C-Flange) Reference
Est. Overall Length (L)
–
Est. Overall Width (W)
–
Est. Overall Height (H)
–
The blue circle callout marks the terminal box location (T/L/R) on the drawing. For Left/Right,
the box itself is drawn mounted on the side of the frame at mid-height (not on top) to match how
it actually sits in the side elevation. This view conventionally looks at the Left/F1 side, so a
Right/F2 box sits on the far side of the motor — it's drawn with a dashed outline (standard
hidden-line convention) since it's physically obscured by the body from this viewing angle; the
end view on the right still shows its true clock position unambiguously. Cable/conduit entry
direction is tracked in the datasheet below rather than drawn on the sketch, to keep it readable.
Schematic side and end-view outline, not to scale/CAD accuracy. Shaft diameter and
center height (D) follow the standard NEMA U/D dimensions for the selected frame; overall L/W/H
use the published LEESON/NEMA height (D+O) and width (P) for frames 42–449T; overall length is
a typical TEFC value (NEMA does not standardize it) and varies by manufacturer, HP, pole count, and accessories (fan cover, terminal box size, cooling jacket). The
C-Face reference shows published NEMA AJ (bolt circle) and AK (register) dimensions for frames
56–449T; frames outside that range aren't covered by this reference and are drawn generically.
Confirm against the manufacturer's certified outline drawing before finalizing foundation,
coupling, or panel layout.
Site & Environmental Conditions
Indoor
Outdoor
meters above sea level (NEMA standard = 1000 m)
°C (NEMA standard = 40 °C)
°C
Application & Accessories
Not Required
Required
Bearing & Lubrication
For VFD service, stray shaft currents can pit bearings (fluting/EDM) — an insulated NDE bearing and/or grounding ring is commonly specified on frames ≥ 184T.
Testing & Inspection
Select the tests to be performed per NEMA MG-1 / IEEE 112 / IEC 60034-2 prior to shipment.
Routine Test (standard)
Witnessed Routine Test
Full-Load Run Test
No-Load & Locked-Rotor Test
Vibration Test (MG-1 Pt. 7)
Sound Level Test
Generated Datasheet
DOL — Direct-On-Line Start
VFD — Variable Frequency Drive
Motor Datasheet
LOW VOLTAGE INDUCTION MOTOR — SELECTION DATASHEET
Output
Frame
Shaft Diameter (DE, std.)
Shaft Center Height (D)
Est. Motor Weight
Est. Overall L × W × H
Voltage / Phase / Hz
Full-Load Speed
Full-Load Current
Locked-Rotor Current
Service Factor
Enclosure / Cooling
NEMA Design / Insul. Class
Temperature Rise
Area Classification
Duty
Continuous (S1)
Site Ambient (Max/Min)
Altitude
Location
Mounting
Orientation
Terminal Box Location
Cable/Conduit Entry
Shaft
Transmission
Driven Load
Space Heater
Painting / Coating
Bearings (DE / NDE)
Lubrication
Grease Type
Bearing Insulation / Grounding
Est. Relube Interval
Testing / Inspection
Engineering disclaimer: This tool provides preliminary sizing guidance only (typical NEMA MG-1
frame practice, planning-level efficiency/PF, and NEC 430-style current multipliers). It is not a
substitute for a certified manufacturer performance datasheet, a coordinated short-circuit/overload
study, or review by a licensed engineer. Locked-rotor current varies with NEMA code letter (B–V);
verify actual values, breaker/contactor sizing, and cable sizing against NEC 430 and the selected
motor's certified datasheet before specifying equipment.