Bearing Fluting Specialists Stop the Attack at the source
Bearing Currents on Motor Drive Units

Bearing Currents on Motor Drive Units

Sunday, September 25, 2022

Using EMF Cores to Suppress Bearing Fluting & Attack 100% Effective in this case.

Why fit Electromagnetic cores to SEW MoviMot’s?
When multiple MoviMot’s are installed into a facility additive effects of High Frequency Current can cause Bearing Failure, Communication Errors, and EMF emissions on Power Supplies.

When removing a MoviMot drive head the Inverter components are contained within removable part and are connected via a plug.

The motor is connected with six motor leads hence there is no links in the motor terminals.

MoviMot Connections

Therefore the windings are separated and each end of the winding is connected to the drive.

Six lead connection within MoviMot

The motor terminals have six leads and are color coded.

Colour Coded Motor Leads MoviMot

The Motor Windings are paired:

Black to White

Pink to Brown

Blue to Yellow

Colour Codes MoviMot

The supply is connected and the AC current

flows in each winding.

e.g. Current flows “Black to White” on the positive AC cycle, and reverses on the negative AC voltage.

The concept of EMF Cores is the NET current flowing through the center of the EMF Core gets filtered at frequencies shown in the chart. Typically starting at 40kHz and above.

Attentuates above 40kHz, doesn't Affect Power or Communications

The motor leads of a MoviMot are required to pass through the EMF cores in both Common Mode & Differential Mode.

When Supply & Return (Counter Current) passes through an EMF Core as in the Light Blue Arrangement the Magnetic flux cancel and only High Frequency Common Mode Noise is filtered.

Common Mode Bearing Current

When the Supply & Return from an individual winding in the MoviMot passes through the EMF Core with the current co current then the Magnetic flux adds and High frequency Differential Current is filtered.

Common Mode Arrangement

The recommended wiring arrangement is to pass ALL six leads through the first EMF Core in Common Mode. The leads all are wound in the same direction and this arrangement protects attack on Lubrication Breakdown (Blackening), and Bearing Attack (Bearing Fluting and Ball Pitting).

Common Mode Wiring Configuration

Differential Mode Arrangement

In differential mode arrangement the Supply & Return Currents are passed through the EMF Cores in the same direction. Both conductors current ADD to the magnetic flux filtering High Frequency Current that Attacks Motor Insulation and Radiates EMF.

Differential Mode Current

Note: The Return Conductor is passed through the opposing face of the EMF Core to the Supply conductor. This ensures the current is flowing in the same direction within the EMF Core.

The reason three separate EMF Cores are used (one for each Phase) in differential mode is that the High Frequency Current may not be in Phase across U V W. If those conductors were to pass through a single EMF Core some opposing flux could cancel and filtering become ineffective.

Mark Gurney: PEng, Motor Analyst, Environmental Auditor

For Help with Suppressing Bearing Currents

Best Practice Motor Management

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