does current flow in to the bearings or not,if does how much?

Thread Starter

kiran4433

Joined Dec 14, 2018
7
doubt.png
hi everyone,
the image shows above has carbon bushes which caries high voltage current connected to the axle ,in this connection does the current directly flows in to ground through axle ,wheel and rail or it also flows into the bearings ,if current does flow in to bearings how much of current out of 600 amps ,700volts flows into bearings
 

Alec_t

Joined Sep 17, 2013
11,517
Welcome to AAC!
Assuming the bearing consists of all metal components then, if there is a path to ground via the bearing support, current will flow. How much current depends on the total path resistance.
 

MaxHeadRoom

Joined Jul 18, 2013
21,207
Some motors/similar devices that are prone to have a build up electrical charge on an armature, typically have a carbon brush fitted against the rotor and connected to Earth ground in order to bleed off any build up.
A common use of this is seen in some mains powered T.M. DC motors.
Max.
 

Thread Starter

kiran4433

Joined Dec 14, 2018
7
Some motors/similar devices that are prone to have a build up electrical charge on an armature, typically have a carbon brush fitted against the rotor and connected to Earth ground in order to bleed off any build up.
A common use of this is seen in some mains powered T.M. DC motors.
Max.
thanks its useful can u suggest any papers to go through for more info
 

Thread Starter

kiran4433

Joined Dec 14, 2018
7
Nothing too complicated, just a earth grounded carbon brush contacting a spot on the armature shaft.
Max.
I understand what u said ,the only doubt I have is ,does any current flows to bearing ,if not,what proper explanation can i give to my friend and if does how to calculate the amount of current that flows to the bearings,
if you have any explanation that could help with my work
 

Picbuster

Joined Dec 2, 2013
1,020
I understand what u said ,the only doubt I have is ,does any current flows to bearing ,if not,what proper explanation can i give to my friend and if does how to calculate the amount of current that flows to the bearings,
if you have any explanation that could help with my work
There are two paths one via the brush(es) one via the bearing(s).
Both do have conductance and are in parallel connected.
As result the current will fly in both but limited by its conductance and there start your trouble.
as brush resistance is high the current will take his way via bearings.
But...... brush resistance is a function of wearing.

Result impossible to calculate in a real live (used) situation.
Measurement is the only way (voltage over the brush/ax connection).
That voltage is a base to find current via bearings.

Picbuster
 

LesJones

Joined Jan 8, 2017
2,687
I think the bearing housing should be insulated from the rest of the metal on the train so that no current can pass through it.

Les.
 

Thread Starter

kiran4433

Joined Dec 14, 2018
7
There are two paths one via the brush(es) one via the bearing(s).
Both do have conductance and are in parallel connected.
As result the current will fly in both but limited by its conductance and there start your trouble.
as brush resistance is high the current will take his way via bearings.
But...... brush resistance is a function of wearing.

Result impossible to calculate in a real live (used) situation.
Measurement is the only way (voltage over the brush/ax connection).
That voltage is a base to find current via bearings.

Picbuster[/QUO
here current initially only flows through brushes and enters in to axle as current is only supplied to brushes by insulating bearing with the help of insulating rings and washers ,my only doubt is that does current flows in to bearings after entering axle.
 

Picbuster

Joined Dec 2, 2013
1,020
Galvanic connections are needed to run a current flow.
If bearings are proper isolated no flow can occur rather than caused by isolation leakage or RF/HF currents.
An other point of ( theoretical) issue on fully isolated bearings; rotation could generate a potential(electronic charge).
The only way is to measure.

Picbuster
 

BR-549

Joined Sep 22, 2013
4,938
It would have to flow thru the grease or lubricating oil, the babbitt bearing material and the housing.

I don't think current would be wanted on a ball or roller bearing.

Just a guess. I would not want any bearing current. Especially hundreds of amps.

If anyone knows of such.....please inform us.
 

Ramussons

Joined May 3, 2013
839
I'm with BR-549.
In actual usage, the Bearing Current is Zero.
If there exists a Bearing Current, that bearing will not last even for a short time. There will be Spark Erosion and Lubricant Burn with a possibility of Flames.
 

Danko

Joined Nov 22, 2017
966
if current does flow in to bearings how much of current out of 600 amps ,700volts flows into bearings
Usually they shunt bearings by brushes.
See https://ep-us.mersen.com/fileadmin/catalog/Products/Power-Transfer-for-Rail-Vehicles/Earthing-Return-Current-Units-ERCU/Earthing-contacts-for-Metro-and-Tram/2-Gaines-into-isolated-wheel-Axial-16X25-200Amp/DS--2-Gaines-into-isolated-wheel-Axial-16X25-200Amp-EN.pdf
"To avoid such damages, it is necessary to use devices shunting the
greatest part of the current through the axles and wheels without
flowing through the roller bearings."

EDIT:
They guarantee 5mOhms resistance of brushes contact,
so voltage on bearings is about 1V@200A.
Therefore it is easy to measure current through bearings by putting voltage 1V
between axle and bearing box (with brushes removed) and measuring current of 1V power supply.
For 600A information see https://ep-us.mersen.com/fileadmin/catalog/Products/Power-Transfer-for-Rail-Vehicles/Earthing-Return-Current-Units-ERCU/Earthing-contacts-for-High-Speed-Trains/3-Gaines-Standard-Axial-20X40-600Amp-HST/DS--3-Gaines-standard-Axial-20X40-600Amp-HST-EN.pdf
 
Last edited:

Thread Starter

kiran4433

Joined Dec 14, 2018
7
Usually they shunt bearings by brushes.
See https://ep-us.mersen.com/fileadmin/catalog/Products/Power-Transfer-for-Rail-Vehicles/Earthing-Return-Current-Units-ERCU/Earthing-contacts-for-Metro-and-Tram/2-Gaines-into-isolated-wheel-Axial-16X25-200Amp/DS--2-Gaines-into-isolated-wheel-Axial-16X25-200Amp-EN.pdf
"To avoid such damages, it is necessary to use devices shunting the
greatest part of the current through the axles and wheels without
flowing through the roller bearings."

EDIT:
They guarantee 5mOhms resistance of brushes contact,
so voltage on bearings is about 1V@200A.
Therefore it is easy to measure current through bearings by putting voltage 1V
between axle and bearing box (with brushes removed) and measuring current of 1V power supply.
For 600A information see https://ep-us.mersen.com/fileadmin/catalog/Products/Power-Transfer-for-Rail-Vehicles/Earthing-Return-Current-Units-ERCU/Earthing-contacts-for-High-Speed-Trains/3-Gaines-Standard-Axial-20X40-600Amp-HST/DS--3-Gaines-standard-Axial-20X40-600Amp-HST-EN.pdf[/QUOTE
thanks for the info ,its useful
 
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