Motion Control in Southern Africa Motion Control in Southern Africa South African Fluid Power Assocation
   
 








 
 

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 (0)11 312 5252
Fax: +27 (0)11 312 5262
Email: drives@varispeed.co.za
www: www.varispeed.co.za
Share via email        

Further reading:

  • Variable speed drive with embedded intelligent services
    3rd Quarter 2014, Schneider Electric South Africa, Electrical switching & drive systems & components
    Altivar Process delivers added value services in the food and beverage, water, oil and gas, metals and minerals, and mining industries, enabling business and process optimisation through improved life-cycle asset management and enhanced energy consumption.
  • Bonfiglioli gears up
    3rd Quarter 2014, Bonfiglioli, Electrical switching & drive systems & components
    Bonfiglioli has built on its strengths in brushless motors, low backlash gearboxes and inverters to create the Mechatronic Drives and Solutions (MDS) division within its global industrial division.
  • Maximum drive efficiency, minimum power consumption
    3rd Quarter 2014, Adroit Technologies, Electrical switching & drive systems & components
    Mitsubishi Electric is one of the top Variable Speed Drive (VSD) suppliers globally with its wide variety of VSDs that offers the right drive solution for every application.
  • Finding perfect pitch
    3rd Quarter 2014, MOOG, Electrical switching & drive systems & components
    A recent enhancement to the Moog AC Pitch System is the self-sensing speed control for turbines that was developed to prevent blades from not being able to move in the event of an encoder failure – the worst case load scenario for the wind turbine.
  • Low noise conveyor system with fast assembly
    3rd Quarter 2014, Tectra Automation, Electrical switching & drive systems & components
    Future-proof production, assembly and packaging lines must be able to deal with smaller batches, more frequent product changes and a large number of product variants. Chain conveyor systems used in production ...
  • Unidrive M meets requirements of paper mill
    3rd Quarter 2014, Emerson Industrial Automation Southern Africa , Electrical switching & drive systems & components
    Unidrive M demonstrates its leading performance capability in the paper industry.
  • Mill gear units for mining
    3rd Quarter 2014, SEW-Eurodrive, Electrical switching & drive systems & components
    A new range of MGU industrial gear units designed specifically for use with grinding mill drive trains in the mining industry has been introduced to the local market by specialist drive engineering company ...
  • Big intelligence for small drives
    3rd Quarter 2014, Tectra Automation, Electrical switching & drive systems & components
    Machine manufacturers and system integrators expect comprehensive functionalities to drive-based motion logic controls, even in electrical drives in the lower power range. They also want to take advantage ...
  • No adaptor required
    3rd Quarter 2014, Electrical switching & drive systems & components
    Bearings International’s new Motodrive range of inline helical and shaft mounted helical gear motors with a direct dedicated standard IEC fitment is footprint interchangeable with other European brands ...
  • Variolution – an innovative new solution
    3rd Quarter 2014, SEW-Eurodrive, Electrical switching & drive systems & components
    Variolution is an innovative new concept from SEW-Eurodrive that helps customers get more bang for their buck by drawing on their strengths developed through repeated business in their industries. Variolution ...
  • Over a million electronic parking brakes a year
    3rd Quarter 2014, Beckhoff Automation, Electrical switching & drive systems & components
    Conventional hand brakes in cars are increasingly being replaced by electronic parking brakes (EPB). These automatically apply the brake during parking and release it during hill starts while adjusting ...
  • The re-invented high-bay warehouse
    2nd Quarter 2014, Beckhoff Automation, Electrical switching & drive systems & components
    Beckhoff’s TwinCAT 3 unites PC control and science for simplified cable robot operation.

 
 
 
Search...

Motion Control Buyers' Guide

         
 
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.