How to Read a NEMA Motor Nameplate
Identify motor voltage, current, speed, service factor, frame, enclosure, and connection information before using ratings in calculations or replacement checks.
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Nameplate field lookup
Read the whole nameplate and the motor’s connection diagram before transferring a rating into a worksheet. The following terms describe common NEMA motor information. The exact product, duty, and manufacturer instructions still determine how the information applies.
| Field | What it describes | Next check |
|---|---|---|
| HP / kW | Rated mechanical output | Not electrical input power or a complete replacement specification. |
| V / VOLTS | Rated operating voltage or listed voltage combinations | Read the corresponding current and manufacturer connection diagram. |
| A / AMPS / FLA | Nameplate full-load current for the stated rating | Do not substitute it for every code-table current reference. |
| PH / Hz | Number of phases and rated frequency | Confirm the actual supply and any separately documented drive application. |
| RPM | Rated speed under the stated load conditions | Not the synchronous speed of a mathematical pole/frequency example. |
| SF | Service factor under the applicable stated conditions | Not blanket permission for continuous overload or operation at any voltage/frequency. |
| FRAME | Mechanical frame designation | Check shaft, mounting, enclosure, and exact dimensional drawing. |
| ENCLOSURE / enclosure abbreviation | Motor construction/environment description | Not a substitute for every environmental or hazardous-location approval. |
| INS CL / temperature rise / ambient | Insulation and thermal-condition information | Distinguish insulation class, rated rise, and permitted ambient conditions. |
| DESIGN / CODE | Different NEMA design or locked-rotor code information | Do not interpret a design letter as a locked-rotor kVA code letter. |
| EFF / PF | Efficiency and power factor at the stated rating | Read any load or test condition; they are different quantities. |
| DUTY / connection diagram / catalog | Operating duty and exact product identification | Retrieve the matching manual and terminal/lead diagram. |
Read a sample plate
Illustrative data only
A hypothetical plate reading “3 PH · 60 Hz · 230/460 V · 24/12 A” shows paired voltage/current information. It does not describe how to move leads or connect a particular motor.
Match the voltage and current entries in the same order and verify that interpretation with the manufacturer data. A motor lead box, replacement terminal board, or separate diagram may contain information absent from the main plate. Record those identifiers as well.
If the diagram is missing or unreadable, the number of leads and the voltage pair alone do not supply a reliable connection method. Obtain the exact motor diagram rather than using a generic lead-color rule.
Keep different current references separate
Nameplate current, code-table full-load current, measured running current, drive output current, and locked-rotor information answer different questions. Record which one a worksheet asks for before entering a number.
The motor circuit reference uses supported code-table data for its stated tasks. The overload reference asks for nameplate information under its own limits. Neither makes all nameplate and measured currents interchangeable.
Gather replacement information
- Record the manufacturer, full catalog number, serial/date information where available, all electrical ratings, duty, and connection diagram.
- Record frame, mounting, shaft, enclosure, driven-equipment requirements, and the actual dimensional drawing.
- Check any drive application, cooling, operating speed range, environmental limits, and special listing separately.
- Keep uncertain or unreadable fields unresolved instead of deriving them from appearance.
This page helps read and collect information. It does not select a motor, approve a replacement, or establish safe wiring or rotation.
Use the VFD compatibility worksheet to compare its stated motor and drive ratings. For the separate base-speed, frequency and slip estimate, use the VFD motor-speed calculator. Neither task establishes a permitted operating speed range or approves a motor replacement.