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:

  • Drive solutions partner for the African continent
    3rd Quarter 2015, Electrical switching & drive systems & components
    The market responsibilities of Hansen Transmissions South Africa (HTSA) on the African continent have been extended beyond the southern region to incorporate the Economic Community of West African States as well as east and central Africa.
  • Aircraft in tow
    3rd Quarter 2015, Siemens Digital Factory & Process Ind. & Drives, Electrical switching & drive systems & components
    Aircraft tractor with Siemens hybrid drives.
  • Servo drive reduces energy consumption by up to 50%
    3rd Quarter 2015, Voith Turbo, Electrical switching & drive systems & components
    Voith Turbo’s advanced new closed loop differential pump (CLDP)servo drive saves substantially on energy costs. The heart of the unit is an integrated servo pump consisting of a servo motor and an internal ...
  • High precision, networked steering shaft assembly
    3rd Quarter 2015, Electrical switching & drive systems & components
    LCA Automation in Affoltern am Albis, Switzerland is a special purpose machine manufacturer with many years of experience in manufacturing equipment for the automotive industry. One of LCA’s core production ...
  • Optimised luxury vehicle production
    3rd Quarter 2015, Tectra Automation, Electrical switching & drive systems & components
    Bosch Rexroth recently supplied a high end German motor vehicle manufacturer with a more efficient handling and distribution solution for the conveyance of interior roof trims along the production line. ...
  • ABB string inverters save on costs
    3rd Quarter 2015, ABB South Africa, Robotics, Electrical switching & drive systems & components
    The recently completed installation of a grid-tied photovoltaic rooftop plant by Genergy and ABB value added provider, All Electrical has enabled the property owner to reduce reliance on daytime utility ...
  • Moving airport baggage handling into the future
    2nd Quarter 2015, SEW-Eurodrive, Electrical switching & drive systems & components
    SEW-Eurodrive’s compact and highly productive mechatronic drive system is the ideal solution.
  • Extended range of variable speed drives
    2nd Quarter 2015, Parker Hannifin (Africa), Electrical switching & drive systems & components
    Parker has extended the AC10 range of compact variable speed drives to a power rating of 180 kW, with power ratings now ranging from 0,2 to 180 kW. The AC10 series is the perfect choice for engineers ...
  • High performance planetary gearboxes
    2nd Quarter 2015, Bonfiglioli, Electrical switching & drive systems & components
    Bonfiglioli’s new TQK series right-angle precision gearbox boasts maximum power density and space saving and covers a wide range of applications where dynamic, high speed, high precision operation is ...
  • WEG generators power Windsor Castle
    2nd Quarter 2015, ZEST WEG Group, Electrical switching & drive systems & components
    A project delivered by Southeast Power Engineering of the UK has seen a mini power station installed on the River Thames at Romney Weir to generate electricity sustainably using environment friendly water ...
  • SEW-Eurodrive targets food and beverage
    2nd Quarter 2015, SEW-Eurodrive, Electrical switching & drive systems & components
    In this year’s Pneudrive Challenge, engineering students have been challenged to design a game changer for a food and beverage factory.
  • Servo-driven plasma cutting table
    2nd Quarter 2015, Tectra Automation, Electrical switching & drive systems & components
    Tectra Automation recently supplied and integrated the drive components for bevel head servomotor-driven CNC plasma cutting tables manufactured by CNC Clear Cut in Pretoria. The Bosch Rexroth servo drive ...

 
 
         
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.