ABB Releases Baldor-Reliance SP4 Shaft Ground Motors

ABB has expanded its Baldor-Reliance SP4 series of electric motors with a new grounded shaft variant. Grounding protects the motor from internal arc flash discharges, reducing the chances of damage and extending motor life.

ABB’s new Baldor-Reliance SP4 motor variant features an integrated shaft-grounding ring. Image used courtesy of ABB

Integrated Shaft Grounding

There is much folklore around grounding in electronics and plenty of confusion around what it means to be "grounded." In the case of electric motors, a grounded shaft does not allow a charge difference between the shaft and other motor components. Doing so reduces the chance of an arc flash discharge between, to, or from the shaft. Grounding is accomplished through a grounded shaft ring that pulls charge away from the shaft and into the case of the motor.

Arc flash discharges occur when a large voltage difference builds up and then jumps across the air space between them. When it does, it acts as a mini lightning bolt, blasting one surface. The temperature in an arc flash can approach that of the sun's surface; metal is literally melted and even vaporized away, permanently damaging the components.

In the case of the electric motor, these arc flash discharges chip away at the shaft and other components. The shaft is now weaker, as its diameter is reduced, and each arc causes the shaft to be more and more out of round. Furthermore, the debris can build up, directly impacting and embedding in other components or being deposited from metal vapor on their surfaces.

Grounded shafts offer an alternative to these problems, extending the motor's life and reducing the unplanned downtime to repair this type of damage.

The Baldor-Reliance SP4 shaft-ground motors are designed specifically for variable speed drive (VSD) applications. Image used courtesy of ABB

Baldor-Reliance SP4 Motor IE4 Efficiency

Besides having a grounded main shaft, ABB's new Baldor-Reliance SP4 motor variant is also designed for efficiency. The SP4 motors feature a NEMA super premium (IE4) efficiency rating, which, according to ABB, can reduce energy losses by 20-40% compared to standard electric motors of the same size. Because of this increase in efficiency, the motors run cooler than traditional electric motors, reducing the need for additional HVAC and cooling costs and minimizing the chances of unplanned downtime due to thermal overload.

VSD or DOL Operations

The SP4 shaft-grounded motors are designed to be a drop-in replacement for other standard-sized electrical motors. They are also designed to be compatible with variable speed drives (VSDs), commonly used to control the speed of electric motors, or for direct on line (DOL) applications. The motor is available in 2, 4, and 6 pole designs, and for sizes of 1-10 hp for the TEFC models and 1-20 hp for the ODP models to suit various industrial and manufacturing operations. 

A simple, drop-in replacement motor designed to outlast the older, conventional motor will always be appreciated. The motors' ability to run cooler and more efficiently makes them a good fit for indoor operations. Hot electric motors add to the cooling load of the building, and the SP4 is a good fit for reducing these operating expenses.