New electric motors with multiple ratings simplify selection and use.
Bryan Sisler, Product Manager for Drives and Motors at AutomationDirect, wrote an article for the February 2020 issue of Machine Design titled Newer Motor Designs Combine Functionality. Here’s a summary, click on the link above for the full text.
A “one-size-fits-all” approach might be acceptable for some types of clothing, but for technical projects one always wants the right component for the task at hand. This is especially important for electric motors as these must be specified for the environment, the load, and efficient and reliable operation.
Using the wrong motor will be inefficient at best, and unworkable at worst. On the other hand, not every design requires a high-end motor, and exceeding specifications can result in excessive costs.
When fewer models of motors can be used for more applications, the result is improved efficiencies in design, procurement, and maintenance. The latest industrial multi-purpose motors meet a wide range of technical requirements with a relatively consolidated number of models. Two styles are:
- Open Drip Proof (ODP)
- Totally Enclosed (TE)
Following are some considerations for selecting multi-purpose motors, also referred to as “4-in-1” motors.
Environment and Application First
The major environmental concerns are temperature, dirt, moisture, and vibration. Applications may call for many different mounting styles, along with ability for a variable frequency drive (VFD) to operate the motor for improved control, reduced equipment wear, and energy savings.
While very specialized motors can be selected to meet the environmental and application conditions, many users find that a few models of multi-purpose motors can satisfy many applications.
ODP: The Simple Solution
ODP motors, with their open construction and sealed bearings, run cooler and are less expensive than other types. They are the simplest and most cost-effective option and are suitable for low dust environments, and they can even withstand dripping water. They are also relatively efficient and offer flexible mounting options.
More Capable Multi-Purpose Options
For more challenging environments, TE multi-purpose motors are generally a better choice than ODP motors. Key features include:
- Flexible mounting
- Continuous-duty air-cooling
- Reversible operation at various voltages
- Higher grade electrical windings
By design, TE construction prevents contaminants from entering the motor. Many styles are cooled by an integral external fan.
Fewer Models for More Applications
It is always important for designers to consider whether an electric motor will be operated with a VFD.
For these motors an additional important requirement is to ensure the motor is VFD-rated if it will be operated in these types of applications, as opposed to simply being suited for standard general purpose (GP) induction across-the-line starting. VFD-rated motors may also be called inverter duty or vector duty.
There is some overlap in specifying ODP and TE multi-purpose motors for applications in machines, conveyors, pumps, fans, and other systems. ODP motors are the most economical choice for benign environments, while TE motors are more suitable where VFDs are used or in environments with contaminants.
Specify Just Enough Motor
A little time spent during the motor specification process can streamline the number of motor types needed, saving money and simplifying design, purchasing, stocking, and maintenance.