Types of NEMA Electrical Enclosure

General information on the definitions of NEMA enclosure types:
For enclosures used in

Non-Hazardous Locations

Type 1 : General Purpose - Indoor

• Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment and to provide a degree of protection against falling dirt.

Type 2 : Drip-Proof - Indoor

• Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment, to provide a degree of protection against falling dirt, and to provide a degree of protection against dripping and light splashing of liquids.

Design of Nema A, B, C and D for Electric Motor Control

Different motors of the same nominal horsepower can have varying starting current, torque curves, speeds, and other variables. Selection of a particular motor for an intended task must take all engineering parameters into account.
The four NEMA (National Electrical Manufacturers Association) designs have unique speed-torque-slip relationships making them suitable to different type of applications:

NEMA design A

• maximum 5% slip
• high to medium starting current
• normal lock rotor torque
• normal breakdown torque
• suited for a broad variety of applications - as fans and pumps

Efficiency of Electrical Motor

Electrical motor efficiency is the ratio between the shaft output power - and the electrical input power.

Electrical Motor Efficiency when Shaft Output is measured in Watt

If power output is measured in Watt (W), efficiency an be expressed as:

η_m = P_out / P_in?             (1)
where
η_m = motor efficiency
P_out = shaft power out (Watt, W)
P_in = electric power in to the motor (Watt, W)

Electrical Motor Efficiency when Shaft Output is measured in Horsepower

If power output is measured in horsepower (hp), efficiency can be expressed as:

η_m = P_out 746 / P_in            (2)
where
P_out = shaft power out (horsepower, hp)
P_in = electric power in to the motor (Watt, W)