Bonding High Voltage Source with Low Voltage Source(s)

  • Thread starter Electabuzz
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  • #1
I'm trying to get a better understanding on how grounding, bonding, and earthing works when high voltage sources interact with lower ones. For example, if you have a 400V AC, 20V AC, and 5V DC source all stored in the same aluminum cabinet (surrounded by a faraday's cage and connected to earth), would there be any disadvantages to bonding the 400V source to the other low-voltage sources. In the scenario I'm looking at, all three sources are connected to external loads/ grounds.

The 400V source connects to its load with much larger wires than the 20V AC and 5V DC sources... if the three are all bonded to each other, will there be any inductive concerns?

Currently the 400V AC source is not bonded to anything however the 20V AC and 5V DC sources are bonded to each other without any issues; the insurance of having the 400V source also bonded would be nice however I'm leaning towards there being some issues with adding a much higher voltage source to the two lower ones.
 

Answers and Replies

  • #2
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Well first and foremost you need to be quite clear as to why you want to connect one side of the floating 400V source to earth.

Earthing implies a protective electrical conductor. That is a conductor that plays no part in the normal operation of the circuit, but is present to provide a manageable discharge path in the event of a fault condition.

For instance your aluminium cabinet should be so earthed.

The use of the term 'bonding', on the other hand implies the connection together of disparate metal parts and so that they are at the same potential so that no person in contact with one part can touch another at a different potential and thereby receive a shock.
Alternatively you may bond together metal parts to prevent sparking, due to different potentials.
The metal parts may be terminals of a power supply or nominally electrically dead.

So what are you trying to achieve?
 
  • #3
Studiot, thank you for your explanation :smile:

Well first and foremost you need to be quite clear as to why you want to connect one side of the floating 400V source to earth. The use of the term 'bonding', on the other hand implies the connection together of disparate metal parts and so that they are at the same potential so that no person in contact with one part can touch another at a different potential and thereby receive a shock.
Alternatively you may bond together metal parts to prevent sparking, due to different potentials.
The metal parts may be terminals of a power supply or nominally electrically dead.

So what are you trying to achieve?
The purpose of bonding the 400V source to the other sources or the earthed aluminium cabinet would be for extra insurance to ensure it is grounded. I believe the 400V source is already grounded outside of the cabinet, however this would be an extra layer of protection in the case that the current ground is damaged accidentally.

Unfortunately, I'm not yet aware of the driving motivation behind this decision. I'm trying to learn about the advantages and disadvantages to how the 20V/ 5V setup will be effected. The EMF generated by a 400V AC wire is much greater than a 20V wire; how will introducing a large EMF affect the other bonded systems? Thanks again!
 

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