National Electrical Code (NEC): The recommendation of the National Fire Protection Association and is revised every 3 years. The NEC determines the divisions, classes, groups, and temperature codes of explosionproof motors.
National Electrical Manufacturers Association (NEMA): A non-profit organization organized and supported by manufacturers of electrical equipment and supplies. Some of the standards NEMA specifies are horsepower ratings, speeds, frame sizes and dimensions, and torques and enclosures.
NEC: The National Electrical Code is the recommendation of the National Fire Protection Association and is revised every three years. City or state regulations may differ from these code regulations and take precedence over NEC rules.
Negative Feedback: A condition where feedback is subtractive to the input reference signal. Negative feedback forms the basis for automatic control systems.
Negative Torque: A torque developed in opposition to the normal torque of the motor. This may occur at starting (common to 2 pole motors) or at some speed below nameplate RPM. This causes "cusps" or "saddles" in the graphed torque curves.
NEMA Design A Motors: Classification of motors by NEMA used on machines such as fans, blowers, pumps and compressors, requiring relatively low starting torque followed by increasing torque with increasing speed up to the full-load speed and torque. Design A motors are differentiated from design B motors by a higher locked-rotor current.
NEMA Design B Motors: Classification of motors by NEMA used on machines such as fans, blowers, pumps and compressors, requiring relatively low starting torque followed by increasing torque with increasing speed up to the full-load speed and torque. This is the most popular motor design.
NEMA Design C Motors: Classification of motors by NEMA used on machines such as reciprocating air compressors and conveyors, requiring relatively high starting torque that is normally greater than the torque required at full-load speed.
NEMA Design D Motors: Classification of motors by NEMA used on machines that impose pulsating loads or require frequent starting of the motor, such as punch press, oil well pumping, and hoist applications. Design D motors are not offered by USEM.
NFPA: National Fire Protection Association. The group that prepares and published the National Electric Code, Hazardous Chemicals, and numerous other such publications.
No Load: The state of a machine rotating at normal speed under rated conditions, but when no output is required from it.
Non-Reverse Ratchet: A feature on vertical motors for use in deep well applications where water lubricated pump bearings are installed. These ratchets stop the shaft from spinning once the power is discontinued and the pump water column is receding. USEM uses a ball-type non-reverse ratchet which has extended life over pin types as used by other vertical motor manufacturers.
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