Vertical motors are electrically similar to horizontal motors, but are mechanically constructed differently because of the unique cooling requirements. Generally, enclosures are designed to handle a wider range of environmental conditions than Horizontal motors. Where footless requirements are required, it is common to apply vertical motors due to the many application advantages to the driven equipment.
Vertical motors are primarily designed to drive pumps. This means they are designed specifically to handle axial or radial thrust. Turbine, mixed flow and propeller pumps usually have high axial thrust; while centrifugal and non-clog pumps normally require a combination of radial and axial thrust. In order to make the ideal selection, it is necessary to have a complete description of all thrust conditions.
Temperature of Insulation Systems
Insulation systems are classified by NEMA by their ability to perform at a specified temperature rise over an ambient temperature constantly for a specified length of time before deterioration and failure.
NEMA MG1-12.421 - Open Motors are rated as follows:
Vertical Hollow Shaft (VHS)
HOLLOSHAFT® motors were designed and patented by U.S. Electrical Motors in 1932. Their primary use has been with deep well pumps. However, development of the turbine pump for industrial purposes has led to a more versatile design.
Weather Protected Type I Enclosure (NEMA MG1-1, 188.8.131.52) is specifically designed to minimize the entrance of rain and dust. These units are normally applied outside rather than indoors. Screens have been added to prevent entrance of debris and rodents. The mesh is 4 per inch. This enclosure is a U.S. standard for all high thrust machines.
Weather Protected Type II Enclosure (NEMA MG1-1, 184.108.40.206) is available on 449 frame and larger. This enclosure is designed with 3 abrupt changes in entrance path of ventilation air so that airborne particles will be discharged without entering the electric parts of the machine. In addition, air velocity is below 600 feet per minute to further minimize the possibility of moisture or dirt being carried into the electric parts of the motor.
It is highly recommended that this enclosure be used whenever premium protection is required. Thrust bearings run at cooler temperatures in this enclosure rather than the TEFC because air is raked over the thrust chamber. As noted in the Modified Vertical Motors Catalog , TEFC carries lower thrust loads per frame and horsepower. This is directly related to cooling methods.
The definite-purpose application of vertical motors dictates a number of construction features that set them apart from horizontal motors. Some differences are obvious—such as a vertical motor typically drives a pump and has a P-base mount without feet and a horizontal motor may have a footed or footless mount with a C or D flange or no flange). Less apparent is the unique capacity of vertical motors to carry external thrust. For optimum service and performance, understanding how construction features affect application and maintenance requirements is important.
Vertical motors can be broadly classified based on shaft type—solid or hollow. Solid-shaft models couple to the pump shaft at the lower end of the motor. The shaft extension on these motors normally has an annular (ring-shaped) keyway to carry the thrust of the pump and a radial keyway to transmit torque. This type coupling is more common on shallow pumps and tanks than on deep-well applications.