Weather-Protected Machine: TYPE I (WPI) weather-protected machine is an open machine with its ventilating passages so constructed as to minimize the entrance of rain, snow and airborne particles to the electric parts. Its ventilating openings are constructed to prevent the passage of a cylindrical rod 3/4 inch in diameter.

Weather-Protected Machine: TYPE II (WPII) have, in addition to the enclosure defined for a type I weather-protected machine, its ventilating passages at both intake and discharge so arranged that high velocity air and airborne particles blown into the machine by storms or high winds can be discharged without entering the internal ventilating passages leading directly to the electric parts of the machine itself. The normal path of the ventilating air which enters the electric parts of the machines are arranged by baffling or through a separate housing to provide at least three abrupt changes in direction, none of which shall be less than 90 degrees C. In addition, an area of low velocity not exceeding 182.9 meters (600 feet) per minute. Wk2 (reflected to motor shaft) =Wk2 (driven equipment) x (driven equipment rpm) (motor rpm)2

Witness: A witness test is a test performed with a customer representative present.

Wk2 (Moment of Inertia): The moment of inertia is expressed as Wk2 in terms of pound-feet squared. It is the product, the weight of the object in pounds and the square of the radius of gyration in feet. If the application is such that the motor is driving through a pulley or gear so that the driven equipment is operating at a higher or lower speed than the rotor, it is necessary to calculate the inertia reflected to the motor shaft. This is an equivalent Wk2 (reflected to motor shaft) = Wk2 based on the speed (rpm) of the motor.

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