A Pragma Group Company

Shaft grounding brush

GrndShafCrrnts1

Aegis SGR



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Voltage without the Aegis Ring



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Voltage with the Aegis Ring



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Bearing with fluting damage

   

Diverting of VFD Shaft Grounding Currents

Aegis SGR™ (Shaft Grounding Ring)

This innovative new approach involves the use of a ring of specially engineered conductive micro fibers to redirect shaft current and provide a reliable, very low impedance path from shaft to frame, bypassing the motor bearings entirely. Due in large part to an increased focus on energy savings, the use of pulse-width-modulated (PWM) variable-frequency drives (VFDs) to control AC motors has grown dramatically over the last few years. While they offer low operating costs and high performance, VFDs are not without their problems. Shaft currents induced by VFDs can lead to motor failures. Without some form of mitigation, shaft currents travel to ground through bearings, causing pitting, fusion craters, fluting, excessive bearing noise, premature bearing failure and costly unplannned motor outages.

Induced Shaft Voltages, which are sometimes called common mode voltage, can be measured by touching an oscilloscope probe to the shaft while the motor is running. These voltages repeatedly build up on the rotor to a certain threshold, and then discharge in the form of a pulse along the path of least resistance, which usually runs through the motor’s bearings to the frame (ground).

Voltage without the Aegis Ring

This innovative new approach involves the use of a ring of specially engineered conductive micro fibers to redirect shaft current and provide a reliable, very low impedance path from shaft to frame, bypassing the motor bearings entirely. The ring’s patent-pending Electron Transport Technology™ uses the principles of ionization to boost the electron-transfer rate and promote extremely efficient discharge of the high-frequency shaft currents induced by VFDs. With hundreds of thousands of discharge points, the SGR channels shaft currents away from AC motor bearings and protects them from electrical damage.

Without some form of mitigation, VFD-induced shaft currents can cause considerable motor/bearing damage. The image “Voltage without Aegis Ring” depicts the Voltage across the bearing which results in current flow through the bearing. The image “Voltage with the Aegis Ring” demonstrates how effectively the SGR™ reduces these currents (and the damage they cause) by channeling them safely to ground.

Fluting: In a phenomenon known as fluting, the operational bearing race wall, forms a “washboard” pattern. This pattern results in vibration and noise. In an HVAC system, this noise can be transmitted throughout a facility via air ducts.