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Chapter 3: Motors
Electrical Theory & Applications for HVACR
THE MOTOR NAME PLATE
InstrucƟons for making electrical connecƟons to a motor are usually included on the motor
nameplate, also called the data plate. The nameplate should be carefully viewed before selecƟng,
replacing, or wiring a motor. Figures 3‐36 and 3‐37 show an example of a single‐phase motor
nameplate and a three‐phase motor nameplate.
NAME PLATE DATA DEFINITIONS
Frames and Type:
Motors of a given horsepower raƟng are built in a certain size of frame or housing.
NEMA has standardized the frame size and shaŌ heights to be used for each integral horsepower
motor. This permits easy replacement or interchanging of motors.
Max Amb:
The maximum ambient temperature at which a motor can be operated
Temperature Rise: The amount of temperature rise permiƩed above ambient air at rated load
Duty (Time / Hours):
All electric motors are designed for either conƟnuous or limited duty. Those
designed for conƟnuous duty deliver the rated horsepower for an indefinite period without
overheaƟng. Limited duty motors deliver rated horsepower for a specified period of Ɵme and will
overheat if operaƟon is extended. Limited duty motors are oŌen used to operate valves, pumps, or
louvers.
Thermal ProtecƟon:
Indicates type of thermal protecƟon provided, if any
FLA (Amps FL):
The rated current (in amperes) when operated at full load
LRA (Locked Rotor Amps):
The rated current (in amperes) if rotor is unable to turn
KVA Code:
A leƩer indicaƟng the starƟng current required; the higher the locked‐rotor‐kilovolt‐
ampere (kVa), the higher the starƟng current surge
Fig. 3‐36: Single‐phase motor nameplate
Fig. 3‐37: Three‐phase delta motor nameplate