Shaded-pole AC motors are another popular motor option for a limited subset of customers and applications. In the food and beverage industries, where pumps are run continuously and both initial and lifetime costs are factors, shaded pole AC motors can offer some significant advantages:
- Low initial cost
- Low cost of ownership due to virtually no maintenance
- Long lifetime (typically only limited by gear life, like brushless DC motors)
- Operate with AC power
- Quiet operation
- No electromagnetic interference (EMI)
Limitations to the shaded pole AC motors should be considered as well. The biggest limitation is the fixed-speed operation of these motors. Shaded-pole AC motors are engineered to operate at a single speed, determined by the gearing ratio incorporated into their design. Encoders and other feedback mechanisms cannot be used with these motors to ensure proper rotational speed, which can lead to flow inaccuracies and variation during use.
Additionally, these motors tend to generate considerable heat, a side effect only exacerbated by continuous use. Typically, a fan must be incorporated into the design to provide real-time cooling of the motor assembly. These motors are not as powerful as the other motor types.
Given the advantages and limitations of these motors, the general recommendation is to consider shaded pole AC motors for continuous-use applications not as sensitive to slight variations in the flow rate. For other applications, especially those involving dispensing, the better choice would be to use one of the other motor types.