Language:

AEGIS® Bearing Protection - Why Shaft Grounding?

 

Bearing Currents

       


50/60 Circulating Currents from Line Voltage in Motors over 500 Frame:


Sinusoidal voltage sources can cause low frequency circulating currents in large machines due to motors' not-perfectly-symmetical design. 50/60Hz operation can result in circulating currents due to motor magnetic asymmetries.

  • Usually present in very large machines only
  • Circulate through the motor bearings, shaft to frame

Info

Best Practice: Interrupting the circulating current is the best approach to mitigating potential bearing damage.

Ref: NEMA MG1 Part 31.4.4.3

Diagram

AC Induction Motors

VFD OPERATION NO VFD -
50/60/ Hz line operation
Motors up to and including 100hp
(Low Voltage)
Motors over 100hp to 500 hp
(Low Voltage - up to 600 volts AC)
Motors over 500hp
(Medium Voltage- over 600 VAC)
Motors over 500 Frame
(Medium Voltage)
Capacitive EDM Current Capacitive EDM Current
High Frequency Circulating Current
Capacitive EDM Current
High Frequency Circulating Current
Low Frequency Circulating Current
50/60 Hz Circulating Current
AEGIS® SGR
AEGIS® SGR
AEGIS® PRO
AEGIS® PRO
(may not be needed)
Install AEGIS® SGR on DE or NDE
Install AEGIS® SGR opposite side of bearing insulation; usually DE
Install AEGIS® PRO Ring opposite side of bearing insulation; usually DE
Install AEGIS® PRO Ring opposite side of bearing insulation: usually DE
n/a Isolate one bearing, usually the NDE to break the circulating current path. Isolate one bearing, usually the NDE to break the circulating current path. Isolate one bearing, usually the NDE to break the circulating current path

Read the AEGIS® Blog

31 Winterbrook Road Mechanic Falls, ME 04256
ISO 9001:2015 Certified
Phone: +1 207-998-5140   Toll Free (U.S.): 1-866-738-1857  Fax: +1 207-998-5143

Email: | Terms & Conditions | For other static solutions»