Motor Nameplate Data
Motor nameplate data is the standardized set of electrical, mechanical, and thermal ratings permanently marked on an electric motor, as required by NEMA, NEC, and CSA standards. It includes voltage, full-load current, frequency, phases, speed, temperature rise, insulation class, duty cycle, horsepower, locked-rotor code letter, service factor, efficiency, frame size, and design code. This data defines safe installation, protection, and operation.
On a shop floor, motor nameplate data is the authoritative reference for electrical design and protection. Electricians use voltage, full-load amps, and phase to size branch circuits and set overload relays based on FLA and service factor. The locked-rotor code letter and design code inform starting current and short-circuit protection. For motor replacement, maintenance uses frame size, HP, rpm, and enclosure type to ensure like-for-like fit. Hazardous-location motors require Class/Division/Zone and T-Code markings for compliance. In asset registers, nameplate data supports lockout/tagout procedures, risk assessments, and safe work practices.
Why must I use the nameplate FLA instead of code-table current when setting overloads?
NEMA MG 1 and NEC treat nameplate full-load amps as the definitive value for that specific motor's thermal design. Tabulated currents assume typical efficiency and power factor, but real motors may differ. Overload devices must protect the actual motor based on its nameplate FLA, service factor, insulation class, and ambient rating to avoid mis-coordination and comply with manufacturer data requirements.
How does the locked-rotor code letter on the nameplate affect short-circuit and starting duty?
The locked-rotor code letter identifies kVA per HP drawn at rated voltage when the rotor is locked. Higher letters (e.g., H, J, K) indicate higher inrush current. Engineers use this for short-circuit studies to assess starting currents relative to upstream device SCCR, voltage-drop calculations for long feeders, and protection coordination to ensure devices allow starting without tripping while clearing faults.
For WorkSafeBC compliance, why is third-party certification and CSA monogram on the nameplate important?
CSA-accepted motors must carry a CSA or CSA c/us monogram, along with submitter details, type designation, production date, electrical ratings, speed, insulation class, and enclosure marking. This demonstrates the motor has been evaluated against CSA/UL standards for safety. Non-certified or mis-marked motors can be cited during inspections as failure to use approved equipment, especially in hazardous locations.