A somewhat confusing aspect of "grounding" is that it is used in two different ways: 'safety ground' and 'electrical noise ground'.
'Safety ground' is is used to prevent adjacent electrical surfaces from having different potentials in order to prevent electrical shock from hurting us. For instance, in your home an electric range's metal surfaces and the nearby water tap are tied together so that in case of an electrical fault in the range (typically 230 volts) when you touch both you won't get electrocuted.
'Safety ground' is is used to prevent adjacent electrical surfaces from having different potentials in order to prevent electrical shock from hurting us. For instance, in your home an electric range's metal surfaces and the nearby water tap are tied together so that in case of an electrical fault in the range (typically 230 volts) when you touch both you won't get electrocuted.
In electric boats the ABYC Technical Information Report TE-30 Electric Propulsion Systems is the same, preventing, say, the motor and shaft etc from being at a different potential in case of a motor/controller fault. Depending on conditions (dampness/sweat) your skin resistance can be low enough that 50+ volts can do some harm.
In 'electrical noise ground' all of the components within a system have a common point electrically so that any impressed electrical noise (typically high frequency like used in motor control) is dissipated across the entire system rendering it ineffective. Typically 'electrical noise ground' is the negative buss as most electronics are referenced to that point.
Being curious, I checked my controller (Kelly). The battery negative and signal returns are common but the aluminium case is not connected to them. So it can be installed in compliance with the ABYC guideline.
John A.
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Posted by: John Acord <jcacord@gmail.com>
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