The electric motor has an impressive history stretching back two or three centuries (depending on whether you count early tinkering or actual working models). But that’s nothing compared with the history of the pump. The most recognizable ancient pump model is probably the Archimedean screw, a primitive device that transports water from lower areas up to irrigated channels or ground via internal, slanted, screw-shaped guides inside a cylinder. Unfortunately, its efficiency was limited by the fact that it could only be powered by a pair of people.
As technology evolved, other forms of power came to be used to power pumps, including gears, pistons, hydraulics, and magnets. Today, electric motors power most pumps, and vertical motors are one of the more innovative ways to do so. In this article, we will explain what makes up a vertical motor, the kinds of vertical motors you can expect to find on the marketplace, and what to look for when purchasing a vertical motor.
Components of Vertical Motors
Vertical motors come in two main types: direct current (DC) and alternating current (AC) motors. DC motors represent the older, more mature technology, and they’re distinguished by employing an electric power source that doesn’t vary (e.g., batteries, power cells). The two most important parts of a DC motor are the stator (a magnet-bearing, stationary section of the motor) and the rotor (a moving, magnetized section that interacts with the stator). The polarities of the magnets within the stator and rotor each oppose the other so that the rotor turns, transforming electric power into kinetic power. Bearings prop up the rotor, ensuring that it remains in its proper place, while a case and insulation protect the motor from physical shocks and contamination.
Some DC motors contain additional elements. Not every motor employs permanent magnets, so these employ spinning brushes that carry the current to the magnetized surfaces inside the motor. A commutator, which is a kind of rotary switch, also helps regulate the power.
AC motors contain most of the same components as DC motors. However, they may also include technology that causes them to operate at a rate that’s steady instead of synchronized with the fluctuations of alternating current. They can also have uniquely shaped rotors (squirrel-cage configurations), employ multiple stator magnets (polyphase motors), employ magnetic reluctance to turn an unmagnetized rotor (reluctance motors), and more.
Popular Types of Vertical Motors
You can find vertical motors in both DC and AC configurations, including both single-phase AC motors (which are more common in non-industrial settings) and 3-phase AC motors (which creates mechanical power by having the rotor turn more slowly than the stator field). However, motor function isn’t the primary way in which vertical motors are differentiated.
Because vertical motors are, by definition, combined with a pumping system, the way in which the two systems are combined creates different categories of vertical motor. One factor to consider is if the motor has a solid shaft or a hollow shaft. Solid shafts function in an essentially identical manner to other electric motors, receiving mechanical energy from the movement of the rotor. Hollow shafts, though, incorporate the pump shaft into the motor’s shaft and connect at the top of the motor.
Motors also get categorized by their thrust capabilities. Thrust requirements equal the mass flow rate multiplied by the exit velocity and depend heavily on the characteristics of the liquid, the pump, and the required direction of flow. Normal thrust machines require minimal thrust, which is typically calculated based on the motor’s horsepower and speed, while high-thrust motors show their capacity based on a percentage of what one would expect from a normal thrust motor. (Typical percentages are 100 percent, 175 percent, 300 percent, and — in some rare cases — 1,000 percent.)
How to Properly Size a Vertical Motor
In some ways, vertical motors don’t significantly differ from horizontal motors in their sizing. Oriental Motor U.S.A. notes, “There are three factors to calculate when sizing a motor; Moment of Inertia, Torque, and Speed.” Dr. Alaa Khamis of General Motors provides similar guidelines, stating that, at the most basic, you should know the speed, load torque, and load inertia you’ll need for your task. Both guides provide required calculations and general guides.
That being said, other considerations must come into play regarding vertical motors. In order to determine thrust, you will need to calculate your thrust load based on tables associated with your chosen motor’s RPMs and horsepower. As mentioned previously, high thrusts are a greater-than-100-percent calculation based off of this normal number.
Finally, the selection of a vertical motor will also depend on the design of the pump system it’s intended to power. Though calculating the main elements of such a system — namely flow and pressure — sounds simple, it presents challenges all of its own. Addressing these concerns is beyond the scope of this guide, but industry periodical Pumps & Systems provides its own guide that can help you better design and/or understand your pump system.
What to Look for When Buying a Vertical Motor
When purchasing any motor, you will need to consider common characteristics such as the motor’s speed, voltage, RPMs, size, and weight. But due to their unique end-use applications, you should look for other elements.
One of these is the pump’s bearing type. Vertical pump motors have different kinds of bearings that indicate their thrust ratings. Angular contact ball bearings allow for normal loads, up to 175 percent loads if paired, and up to 250 percent loads if three are stacked. Spherical roller bearings allow for 300 to 500 percent thrust loads. Hydrodynamic bearings also facilitate very high thrust loads and have an exceedingly long operational life.
Another is case design. Different applications can expose the pump to various environmental risks and wear-and-tear scenarios, including overheating. Enclosures include basic weather protection, complete enclosure with fan cooling, hazardous-location protection, and submersible.
Finally, we have already mentioned in previous sections the importance of selecting between a solid shaft or a hollow shaft vertical motor.
Applications and Industries
Vertical motors and their concomitant pump systems are typically used to move fluids of some sort. As such, they are used in:
- Accessing shallow or deep-water wells
- Oil and gas generation
- Power generation and utilities
- Ground water development
- Waste treatment
- Condensate extraction
- Water treatment
Vertical motors and their concomitant systems have several more or less standard accessories, which include the following:
- High Thrust Bearings: As mentioned in a previous section, the most common types of bearings include angular contact ball bearings, spherical roller bearings, and hydrodynamic bearings.
- Steady Brushing: Designed to shore up hollow-shaft motors, this brass brushing helps stabilize the shaft.
- Non-Reverse Ratchets: These ratchets help prevent the flow of water from striking the pump impeller when the motor gets turned off, preventing damage.
- Self-Release Couplings: Designed to disengage in the case of a power failure, this prevents the motor’s drive coupling from unscrewing and damaging the pump.
Tips for Finding and Buying a Vertical Motor
Purchasing a crane motor isn’t an insignificant buy, and you’ll want to make your selection from a trusted source. Surplus Record has decades upon decades of experience in helping buyers find trustworthy equipment and aiding sellers in offloading of it. Once you’ve determined exactly what kind of vertical motor you’d like, type the term into the search bar at the top of our website to get started.
In addition to our classified listings, we have connections with multiple dealers who specialize in all kinds of different equipment. You can find dealers in your area or by name. Click on the “Dealer Search” drop down menu at the top of the page to begin your search.