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Aegis Ring

Problem

Induced Shaft currents damage bearings

The use of variable – speed drives with AC motors induces electrical currents on the motor shaft. Once they exceed the resistance of the bearing lubricant, these currents discharge to ground (typically the motor housing), causing fusion craters in the bearings. Over time, these craters increase in size and number, resulting in frosting, pitting, fluting and eventually bearing failure. This type of premature bearing failure can cost thousands of dollars in increased maintenance and lost production.

Solution

Aegis – the world’s most effective shaft grounding brush

The new aegis conductive MicroFibreTM shaft ground brush prevents electrical damage to motor bearings by safely channeling harmful shaft currents to ground. Using proprietary Electron Transport TechnologyTM the conductive micro bres inside the aegis provide the path of least resistance for damaging shaft currents, preventing electrical damage to motor bearings and dramatically extending motor life.

 
 

The longest lasting protection available

Not only is the aegis the world’s most effective grounding brush, it offers the longest lasting protection available.

Maintenance – free
• Unaffected by dirt, grease, or other contaminants
• Lasts for life of motor

Fast easy installation
• Easily installed in minutes – even in the field
• Mounts on either end of motor shaft
• Simple screw – on mounting brackets
• No machining required.

Sizes for most NEMA and IEC motors
• Available in standard sizes for
• NEMA and IEC frames
• Shaft diameters: 0.311” to 6.020” (8mm to 153mm)
• Larger sizes available upon request
• No RPM limitations

About Shaft Current

Comparison of technology to eliminate electrical damage to bearings

In the electrical AC motor industry, the use of variable speed drives greatly increases generation of electrical current on the shaft of the AC motor and causes electrical damage to bearings unless a mitigation strategy is employed

Damaging shaft current is built up in AC motors when controlled by variable frequency drives (VFD) using pulse width modulation (PWM) to control the AC motors. These drives use insulated gate bipolar transistors (IGBT) with extremely high switching speeds which create common mode voltages because of the V/T due to parasitic capacitive coupling between the stator and rotor. The result is shaft current that dischargers through the motor bearings from shaft to frame causing fusion craters in the bearing race wall, ultimately resulting in severe frosting and fluting. Without protection this phenomenon occurs immediately upon operation of the motor/drive system and continues until costly failure occurs.

Aegis shaft grounding ring provide a revolutionary solution to extend bearing life of the motor. The aegis solution overcomes the obstacles encountered with the application of other technologies. Key aegis benefits are:

• Easy to install
• Long term effectiveness
• Low lifetime cost
• Maintenance free

Easy to install

Aegis is easily installed with external mounting brackets that clamp directly on to the motor end bell. Installation may be on the drive end and /or the non-drive end of the motor, depending on the application. Aegis may also be press fir into the motor housing. Insulating sleeves and ceramic bearings are custom installations by the motor manufacturer or service shops. External copper or carbon brushes require special brackets for installation.

Long term effectiveness

Continuous operating results from aegis testing show consistent and highly reliable performance in the functional operation without any decrease in effectiveness over time. This is because aegis works through the principle of ionization and patent pending electron transport technology. The aegis solution provides a continuous discharge path for shaft current and extends bearing life by providing an alternate path for shaft current to bypass the bearings. Ceramic bearings and insulation sleeves prevent current from passing through the bearing race but do not remove the shaft voltages which may then be discharged through the load. Conductive grease will become less effective over time as the conductive particles separate. The grease also may not perform properly as a lubricant. Copper and carbon brushes become less effective over time because oxidation builds up on the shaft and dirt and grease reduce their conductivity.

Lifetime cost of solution

Aegis provide low cost solution with no parts to wear out and continuous operational effectiveness over the life of the motor. Ceramic bearings are costly to implement and require long lead times. Insulating sleeves are costly to install and may lose effectiveness if dirt and particles build up. They also cause grater heat build-up at the bearing which reduces bearing life. Conductive grease loses effectiveness over time and requires replacement which increases maintenance costs. Spring loaded brushes require maintenance and replacement which increase the lifetime costs.   

Maintenance free operation

Aegis is maintenance free and highly reliable. Once aegis is installed it continues to operate without any adjustment, replacement or maintenance with no frictional wear over time. Ceramic bearings are installed by motor manufacturers and should not require maintenance. Insulating sleeve may require maintenance if contamination builds up during operation. Conductive grease will require periodic replacement. All types of contact friction brushes (copper or carbon) require regular and careful maintenance to ensure their effectiveness. 


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