According to the US Centers for Disease Control, drinking water chlorination and treatment was one of the ten greatest public health achievements of the 20th century. And of course, you can't effectively treat water without pumping it. Vertical hollow shaft motors are an essential part of the modern water pumping process.
And not just for drinking water: Hollow shaft motors have large roles in wastewater, agriculture, mining, and chemical processing. As a rule, these motors do not always need to run at full speed. So it makes sense to run them at reduced speed with variable frequency drives.
The downside of VFDs is that their pulsed voltage output can cause problems in electric motor windings and bearings. The windings are not such a problem in modern "inverter duty" motors. But many motors, vertical and horizontal, still don't include electrical bearing protection, and are vulnerable to electrical bearing failure.
The best way to protect vertical hollow shaft motors against electrical bearing damage from VFDs starts with an AEGIS® Shaft Grounding Ring at the lower bearing. For motors over 100 hp (75 kW), the upper bearing must be electrically isolated from the shaft and frame. This is usually done by installing an insulated bearing, with either a ceramic rolling element or an aluminum oxide coated inner or outer ring. Alternatively, if the motor has a bearing carrier, the bearing carrier can be treated with an insulating aluminum oxide coating.
There are scores of specially trained motor repair facilities, AEGIS Trained Installers, who can both install the grounding ring and bearing insulation (where necessary).
There are also vertical hollow shaft motors that come with electrical bearing protection built in. All US Motors CORRO-DUTY Inverter Duty Vertical HOLLOSHAFT® Motors include an AEGIS ring and insulated upper bearing (where necessary).
Wolong's GE Industrial Motors also offers fully-protected vertical hollow shaft motors. All Ultra+™ Vertical Hollow Shaft with WPI motors include AEGIS rings. And so do motors over 40 hp (30 kW) in the Ultra™ TEFC Vertical Hollow Shaft Inverter Duty with Bearing Fluting Protection line.
Those motor lines come with an AEGIS ring, standard. Other motor lines and manufacturers can add an AEGIS ring as a mod, but modification is not as convenient as, and takes longer than, ordering a standard catalog motor.
So whether you get a new motor with AEGIS installed, or have a grounding ring installed by a trained repair contractor, there's no reason not to protect vertical hollowshaft motors with AEGIS.
AEGIS Rings also come with a 2-year extended warranty against bearing fluting damage. No other form of protection against VFD-caused bearing damage offers a warranty like this.
To learn more about AEGIS shaft grounding and best practices for electrical bearing protection, sign up for a training. We offer monthly live training webinars, and - pandemic situation allowing - we can also visit your site and give an in-person training, with an emphasis on your specific needs.