classic | mobile
 

Search...

 

Motor bearing current phenomenon
3rd Quarter 2011, Electrical switching & drive systems & components


Yaskawa application note.

Introduction

Since the introduction of PWM inverters, it has been recognised that PWM inverters introduce motor shaft voltages and bearing currents. The bearing damage in inverter-driven motors is mainly caused by the shaft voltage and bearing currents created by the common-mode voltage and its sharp edges. All inverters generate common-mode voltages relative to the power source ground that cause coupling currents through the parasitic capacitances inside the motor. The main source of bearing currents is the capacitance-coupling currents that return via the motor bearings back to ground.

This paper discusses the relationship among common-mode voltage, motor shaft voltage and bearing currents using parasitic capacitances and its mathematical representation inside the motor.

Common-mode voltage in inverter-driven AC machines

In a three-phase AC system, the common-mode voltage can be defined as the voltage difference between the power source ground and the neutral point of a three-phase load. If the load is an AC motor, the neutral point of the load means the stator neutral of the motor. It is important to define the common-mode voltage in mathematical terms in order to compare its characteristics among different types of source and load combinations.

In three-phase AC loads, the phase to ground voltages can be written as the sum of the voltage from phase to the neutral point of the load and the neutral point of the load to the system ground. As per the definition, the common-mode voltage is the voltage across the neutral point of the load and the system ground.

Readers interested in a full mathematical analysis of the subject together with some recommended approaches to prevent bearing current damage in AC machines can find the complete application note at http://instrumentation.co.za/+C15396


Credit(s)
Supplied By: Varispeed (Div. of Hudaco Trading)
Tel: +27 11 312 5252
Fax: +27 11 312 5262
Email: drives@varispeed.co.za
www: www.varispeed.co.za
Share via email     Print this page  

Further reading:

  • Varispeed receives Yaskawa award
    2nd Quarter 2017, Varispeed (Div. of Hudaco Trading), News & events
    Varispeed has received the 2016 Yaskawa Drives and Motion division partner of the year award for the Europe, Middle East and Africa regions and presented during the Yaskawa Europe International Partner ...
  • Siemens servodrive supplemented with Profinet
    2nd Quarter 2017, Siemens Digital Factory & Process Ind. & Drives, Electrical switching & drive systems & components
    The performance optimised and easy to operate servodrive system from Siemens consists of a Sinamics V90 servo-converter and a Simotics S-1FL6 servomotor and is now also available with Profinet, the Ethernet ...
  • Everything an engineer needs
    2nd Quarter 2017, RS Components SA, Electrical switching & drive systems & components
    RS Components offers everything engineers need to design, develop and deploy world-class motion control solutions. From adding smart capabilities and upgrading systems, to dealing with sustainability ...
  • New assembly cells for geared motors
    2nd Quarter 2017, SEW-Eurodrive, Electrical switching & drive systems & components
    SEW-Eurodrive Cape Town has invested in new assembly cells for geared motors to speed up production, increase quality and reduce wastage. The branch also plans a new assembly cell for electronics in the ...
  • SEW-Eurodrive supplies gear units to Kazakhstan
    2nd Quarter 2017, SEW-Eurodrive, Electrical switching & drive systems & components
    One of the largest orders in the history of SEW-Eurodrive South Africa for its MC Series industrial gear units is being supplied to a gold mining project in Kazakhstan, which will see the assembly and ...
  • Another SA first for SEW-Eurodrive
    2nd Quarter 2017, SEW-Eurodrive, Electrical switching & drive systems & components
    SEW-Eurodrive has successfully supplied Movitrac LTP-B Eco HVAC drive units to DSV Healthcare in Meadowview, Johannesburg. This is the first application of the new technology in South Africa and was designed ...
  • Power quality and motor analyser
    2nd Quarter 2017, Comtest, Electrical switching & drive systems & components
    Fluke has introduced the new Fluke 438-II power quality and motor analyser, adding key mechanical measurement capabilities for electric motors to the advanced power quality analysis functions of the Fluke ...
  • VLT automation drives from Danfoss
    2nd Quarter 2017, Bearing Man Group t/a BMG, Electrical switching & drive systems & components
    BMG’s Danfoss range includes the VLT decentral drive FCD 302, designed for installations where multiple AC motors are spread around a facility. Typical applications include bottling, food preparation ...
  • Mechanical drives in a nutshell
    1st Quarter 2017, Siemens Digital Factory & Process Ind. & Drives, This Week's Editor's Pick, Electrical switching & drive systems & components
    The editors of Motion Control and SA Instrumentation & Control recently paid a visit to the Mechanical Drives factory in Isando, Johannesburg to find out how Mechanical Drives fits into the greater Siemens picture.
  • Full silos
    1st Quarter 2017, Yaskawa Southern Africa, Electrical switching & drive systems & components
    The mill operator can adjust all parameters with Zenon software from Copa Data.
  • Ready for Industry 4.0
    1st Quarter 2017, Tectra Automation, This Week's Editor's Pick, Electrical switching & drive systems & components
    Bosch Rexroth’s IndraMotion MLC control system enhances automation performance and flexibility.
  • New range of VSDs
    1st Quarter 2017, Electrical switching & drive systems & components
    Magnet has extended its range of Schneider energy management and automation systems to include the new Altivar ATV320 variable speed drives.

 
 
         
Contact:
Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronic Buyers Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Other
Terms & conditions of use, including privacy policy
PAIA Manual





 

         
    classic | mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.