Slip Rings for Bearing Protection

For many years, Mercotac® Brushless Slip Rings have been the top choice for a diverse range of industries and applications, including for Bearing Protection, due to their various advantages, such as

• Diverting motor shaft voltage to protect bearings from damage
• Continuous 360 degree rotatio
• Long life without any maintenance
• Low resistance

With the advent of motors controlled by VFD’s (variable frequency drives) a new problem surfaced which damages the ball bearings. This type of damage can also happen from asymmetry in the motor’s magnetic circuit and unshielded power cables. VFD’s different electrical waveform causes an electrical voltage to build up on the motor shaft. When the voltage is high enough to overcome the insulation of the bearing grease the voltage will arc or cause an electrical discharge through the bearing balls. This discharge causes micro pitting. Even a few volts can cause this damage. Over time, the pits increase and become deeper and the bearings prematurely fail. For larger motors, like the ones used in commercial HVAC systems this can be an expensive proposition.

One costly way to fix this problem is to use ceramic ball bearings as they do not conduct electricity. An alternate more economical way to alleviate the bearing arcing is to provide a ground for the motor shaft which bleeds off any induced voltages.

Grounding the shaft of a Variable Frequency Drive controlled motor will eliminate the damage to the bearing balls by electrical discharge. By using a Mercotac brushless slip ring to electrically ground the shaft, there exists no possibility of discharge through the bearings.

Sometimes, Mercotac products are even used in place of bearings for specialized applications, with the added benefit to allow for power and data signals to pass through them.

The Model 110 has been used as an electrically conductive bearing to enable a rotating electrospinning apparatus.

Electrospinning is a fabrication technique for making nanofibers of polymers, ceramics, composites, and metals. It can also be used to assemble nanoparticles by aligning them to reduce Gibbs Free energy. An automated electrospinning apparatus was designed and patented by H. L. Simons in 1966.

This type of apparatus creates a method for uniform electrostatic spinning production. Additional patents and various related devices have been developed subsequently. The collection system power supply ground is attached to the polymer fiber collection plate for putting the fibers in order.

Mercotac™ Models 110 and 205 are commonly used for this application, typically for the collection system in electrospinning applications along with a high voltage variable power supply and brush electric motor.