Drives and Control Solutions

Motors, Control Solutions, Power Transmission and Advanced Motion Technology                                                                 

April 18, 2022


DCS HELUKABEL Extending Service Life of Electric Motors 1 400

When operating electric motors with frequency converters, undesirable bearing currents often occur that can significantly impact the service life of the rolling contact bearings. Scientists at TU Darmstadt have investigated these bearing currents - and found out that they can be reduced in some cases with the help of screened motor supply cables.

Bearing currents are undesirable currents that occur during the operation of electric motors. They flow through the roller bearings that connect the movable rotor to the fixed motor stator. Bearing currents occur mainly in drives where the speed is changed with the help of a frequency converter and can cause considerable damage to the bearings. Particularly in cases that have an inappropriate grouding concept, bearing currents with high current densities can occur, which melt or even steam the metal in the bearing ring. The result is craters and so-called riffles in the roller bearing, which become noticeable with increased vibrations and wear even faster. As a result, the bearing often fails only a few months after installation.

There are four kinds of bearing currents, each of which is influenced by different factors and has varying degrees of impact:

  • •Capacitive bearing currents are caused by the voltage across the bearing changing and compensating the currents flowing. These are typically too small to be harmful.
  • Discharge bearing currents (EDM) are pulsed discharge currents. They can occur if the voltage increases in the bearing across the lubricant film until it is electrically broken.
  • Circular bearing currents are circular currents in the electrical machine. This is caused by a high-frequency magnetic ring flux around the shaft, which induces a voltage along the shaft.
  • Rotor-to-ground bearing currents can occur if the rotor of the electric drive is additionally grounded through a gearbox or another device and its ground impedance is lower than that of the stator. The current flows proportionally from the motor housing through the bearings into the shaft and across the ground connection of the rotor.

However, by designing the bearing appropriately, using hybrid or ceramic bearings as well as brushes, filters and grounding rings, design engineers have some options to reduce and avoid these unwanted currents.

Shielding Makes the Difference

DCS HELUKABEL Extending Service Life of Electric Motors 2 400

A decisive criterion is the selection of the right motor cable - this was the result of a study by the Institute for Electrical Energy Conversion at the Technical University of Darmstadt, carried out with the cooperation of HELUKABEL. The scientists compared the occurring bearing currents for cable types with and without screening in several test setups. In the process, they found out that rotor-to-ground bearing currents in particular can be significantly reduced by using shielded cables.

Shielded cables are a simple and effective method to protect rolling-contact bearings from premature wear and failure. An additional advantage: their shielding also prevents unwanted electrical radiation to other devices and thus contributes to the electromagnetic compatibility (EMC) of the entire system.

In its tests, the team from the TU Darmstadt used HELUKABEL motor cables of the type TOPFLEX®-EMV-UV-3 PLUS 2YSLCYK-J. This double-shielded cable is designed for interference-free operation of frequency converters. Furthermore, it is UV and weather resistant and therefore suitable for outdoor use. HELUKABEL's TOPFLEX® series comes in many versions according to different requirements - and has an extensive range of servo and feedback cables for industry and mechanical engineering.

UL/CSA motor cable products include:

  • TOPFLEX® 600 VFD: XLPE Insulation, EMC-preferred Type, Flexible Motor Power Supply Cable, Oil-resistant, NFPA 79 Ch. 4
  • TOPFLEX® 650 VFD: XLPE Insulation, EMC-preferred Type, Flexible Motor Power Supply w/ Control Conductors, Oil-resistant, NFPA 79 Ch. 4
  • TOPFLEX® 1000 VFD: XLPE Insulation, EMC-preferred Type, Flexible Motor Power Supply w/ 3 Symmetrical Ground Conductors, Oil-resistant, NFPA 79 Ch. 4
  • TOPSERV® 600 VFD: XLPE Insulation, EMC-preferred Type, Highly Flexible Motor Power Supply Cable, Oil-resistant, NFPA 79 Ch. 4
  • TOPSERV® 650 VFD: XLPE Insulation, EMC-preferred Type, Highly Flexible Motor Power Supply w/ Control Conductors, Oil-resistant, NFPA 79 Ch. 4

DCS HELUKABEL Extending Service Life of Electric Motors 3 400





Editor's Pick: Featured Article

DCS HELUKABEL Critical Keys to Selecting Right Cable Manufacturer 1 400

As we began 2022, global material shortages and rapidly increasing costs have now become the new reality. The types of materials that have suddenly become difficult to procure are wide-ranging and include computer chips for automotive manufacturing, wood for new construction, and electrical components – just to name a few.

These shortages have created great uncertainty, which is reflected in a recent poll of contractors in the U.S. by the Chamber of Commerce. They reported:

  • •83% are experiencing product delays.
  • •71% are struggling to meet schedule requirements.
  • •68% are experiencing delays expected into 2023.
  • •58% are putting in higher bids on projects.
  • •53% are saying major project shutdowns/delays are a top concern.
  • •41% are saying material shortages continue.
  • •39% are turning down work opportunities.

One of the major material components that affect the cost and availability of wire and cable is copper. This widely used metal, which traditionally has been a volatile commodity, has been steadily increasing in price, which is due to several supply and demand issues.

Read more



Motors for RoboticsTradeoff 1: Torque Density vs. Size 

When calculating the torque requirements for robotic joints, you may run into the first tradeoff: How can you increase the torque in a robotic motor without increasing its size? 

In the frameless motors used in robotic joints, torque increases in direct proportion to an increase in motor length, or as the square of an increase in diameter. In other words, doubling the diameter produces a fourfold increase in torque, known as the D2L rule. In order to achieve the torque required to move and hold substantial loads, the most common approach is to use a larger-diameter robotics motor rather than a longer one, which would make the joint too large and difficult to integrate into your overall design. 

Read More



Hydrogen EnginesHydrogen is an increasingly popular energy carrier. It can be readily produced from water using renewable electricity, and it burns without any greenhouse gas emissions. It is colorless, odorless, and does not spill. It’s no wonder there is a great interest in hydrogen engines as a part of destination zero. 

In this article, Cummins explains how hydrogen fuel can power a vehicle by comparing the similarities and differences between hydrogen and diesel and gas engines and provides some examples of hydrogen engines in mobility and transport. 



Read More


Product News

  • Prev
  AutomationDirect has added drive isolation transformers from Hammond Power Solutions ...
  The new SPS30 AC/DC In-Line Power Converter is a compact, cost-effective device that ...
  At less than 25mm length (+ lead-wires) and 13mm diameter our new pressure sensor ...
  Mersen is pleased to announce non-indicating versions of its popular A2D and A6D ...
  Littelfuse Inc., an industrial technology manufacturing company empowering a ...
  AutomationDirect has added additional safety mats, edges, and bumpers from ASO Safety ...
  Festo’s new manually adjustable VFOE meets all the criteria users are seeking in a ...
  Recently, Emerson introduced the TopWorxTM DX PST with HART® 7. Units provide ...
  Franklin Electric Co., Inc.brand Pioneer Pump® announces the launch of the ...
  Optical sensors detect an object by emitting light beams, which ...

New Product

Augmented Intelligence Platform for Oil and GasEZ Ops, the provider of oil and gas operations software that identifies top priorities to produce the cleanest and most profitable hydrocarbons in the world, has announced the second release of its augmented intelligence operations platform with new capabilities for dynamic routing and day scheduling. 

EZ Ops latest platform release helps operators efficiently plan their daily schedule in under three minutes with certainty they are doing highest value work during their shift, with the least drive time and lowest greenhouse gas emissions. Intelligent schedules and routing draw on algorithms that compute millions of internal and external data including production data, inspection schedules...

Read More


Latest News

  • Prev
  The ABB #BuildtheFuture Roadshow delivers the latest electrical products, services, ...
  Global industry is accelerating its investment in energy efficiency in the next five ...
  In March 2022, the new edition of the installation standard IEC 61918:2018/AMD1:2022 ...
  On this episode of the Allied Expert Advice podcast, Carlos Riano, Senior Offer ...
  Advanced Micro Controls Inc. (AMCI) has realized growth throughout the Midwest United ...
  Ballard Power Systems recently announced that the company has launched a three-year ...
  Discover the difference a Gutor-backed setup can have on your business and ...
  Control Techniques Engineers step up to the plate, in record time, to tackle the ...
  ABB Ability™ Smart Melt Shop digitally connects all steel melt shop processes ...
  Following the announcement made by Bavarian Prime Minister Dr. Markus Söder in the ...
Kerrwil Publications Great Place to Work. Certified December 2019 - December 2020

538 Elizabeth Street, Midland,Ontario, Canada L4R2A3 +1 705 527 7666
©2022 All rights reserved

Use of this Site constitutes acceptance of our Privacy Policy (effective 1.1.2016)
The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of Kerrwil