Shaft Grounding


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Shaft Grounding

Prevent Bearing Damage

Premature bearing failure is a major cause of motor downtime and costly repairs. Helwig Carbon uses proven carbon brush technology in a variety of bearing protection kits for motor shafts grounding. Our kits effectively divert induced electrical currents away from the bearings, protecting them from damage and failure.

Unprotected bearing damage due to fluting

Unprotected bearing damage due to fluting

Helwig Carbon Bearing Protection Kits (BPK) to Fit Motors of All Sizes

Helwig Carbon bearing protection kits (BPK) fit a variety of motor shafts, offer several mounting options, and are easy to install and maintain. BPK will deliver many years of superior performance in shaft grounding, typically outlasting the unit they’re installed on.

Bearing Protector Kit Selection Guide

BPK-IM2

BPK-IM2

Small Motor Option
Brush Dimensions:
.125 x .187 inch
3.2 x 4.75 mm
Kit Dimensions:
.241 x .75 x .75 inch

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BPK-4

BPK-4

Standard Option
Brush Dimensions:
.375 x .25 inch
9.5 x 6.3 mm
Kit Dimensions:
.5 x 1.5 x 1.38 inch

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BPK-S

BPK-S

Sealed Option
Kit Dimensions:
.45 x 1.63 x 1.50 inch
11.4 x 41.4 x 38 mm
Brush Dimensions:
.375 x .25 inch
9.5 x 6.3 mm

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BPK-AM

BPK-AM

Large Motor Option
Brush Dimensions:
.787 x .394 inch
20 x 10 mm
Kit Dimensions:
.63 x 2.09 x 1.26 inch

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C-UR-US

UL Approved Shaft Grounding Kits

Helwig's BPK-IM2, BPK-4, BPK-S, and BPK-AM Bearing Protection Kits are UL Recognized Components for both U.S. and Canada.

PDF: Helwig Carbon - The Bearing Protector™

What causes bearing damage?

Variable frequency drives (VFD) used on AC and DC motors produce induced electrical currents on the motor shaft. This current seeks the path of least resistance to ground which is typically through the motor bearings. When the current passes through the bearings electrical arcs take place leading to fluting, pitting, and bearing damage. The fluted or damaged bearing surface causes noise, vibration, and premature bearing failure. Bearing failure due to these induced electrical currents is one of the most common causes of motor downtime.

Where do you need bearing protection?

  • Motors with VFD
  • HVAC units
  • Pump motors
  • Fans
  • Air handling
BPK-IM2 on a 5/8 inch motor shaft

BPK-IM2 on a 5/8 inch motor shaft

Helwig Carbon is your best choice for dependable bearing protection.

Effective shaft grounding and bearing protection from Helwig Carbon will divert the current from the motor shaft and provide the lowest resistance path to ground in an economical product. The result is the lowest shaft voltage and maximum discharge to ground through the kit rather than through the bearings or other components.

Major OEMs choose Helwig Carbon’s solution as their preferred method to protect motor bearings. Unlike other options, this carbon brush technology uses a proprietary silver graphite material that provides superior voltage minimization. Advantages include:

  • Longevity: will typically outlast the unit it is installed on
  • Most effective technology proven to minimize shaft voltage and damaging currents
  • Provides lowest resistance path to ground
  • Low to high current carrying capacity
  • Stock kits fit most motors and multiple shaft sizes
  • Easy to install and maintain
  • Numerous options for wide variety of conditions
  • Internal mount options avoid exposure to outside and contaminated environments

PDF: Bearing Protector Case Study

Lab: Shaft Grounding Test on a 0.75 HP 230V Motor

Testing on a 0.75 HP motor proved that a Helwig Bearing Protection Kit (BPK) is an effective shaft grounding solution. A Helwig BPK (model BPK-IM) was applied to the 0.75 HP motor. It consisted of an internal mounted grounding brush holder, with a proprietary silver graphite brush.

Measurements were taken for peak-to-peak voltage, number of discharges.

Lab: Shaft Grounding Test

Shaft Voltage Unprotected

Shaft Voltage Unprotected

More Effective at Reducing Shaft Voltage

Helwig Carbon’s shaft grounding minimizes shaft voltage and electrical noise. This graph shows induced shaft voltage with the Helwig BPK-4 vs. a carbon fiber ring. Lower value equals more effective bearing protection. Peak-to-peak voltage for Helwig’s solution is more than 5 times lower than the carbon fiber ring, which significantly reduces the risk of current flowing through the bearing.


Shaft Voltage with Carbon Fiber Ring

Shaft Voltage with Carbon Fiber Ring


Shaft Voltage BPK-4

Shaft Voltage BPK-4

These results illustrate that a Helwig BPK effectively ensures against the risk of bearing damage, therefore improving the life of the motor.