Dissociative Identity Disorder

Rob Eagle:

. . .

Volt drop - volt drop limits, for installations, are defined in 7671, other than that it depends upon the equipment itself and its tolerance to voltage fluctuations, switch-mode power supplies, for example, generally work anywhere in between 90 - 260V so fairly tolerant to volt drop at 230V, other things may not be so, i.e. lamps. 

Now we are getting somewhere! Fluctuation in supply pressure, as compared with drop of potential along a conductor. Not the same thing. We need to be sure what we are talking about. I agree that in this case we need a simple term to describe what is happening. "Electro-motive force deviation" is too ponderous a term. If we need to quantify this, there is surely no harm in stating the quantifying unit?


I do maintain that my physics teacher was right in discouraging the term "volt drop" in analysis of an electrical network, even though the penalty may have been a bit heavy. I discouraged it myself in my lecturing days. Students using the expression in an ambiguous way tended to lose the plot.


One problem is that some basic units of measurement have no formal definition; we must use some inadequate synonym, e.g. "electrical pressure" for electro-motive force. Hence the customary usage of simple terms like "voltage". It does no harm where we need no rigourous analysis. "Potential" is of course a word with a broader meaning - "capability of achievement".  


It is interesting to note that in devices like motors, transformers, etc., engineers sometimes use the term "back e.m.f." rather than "back voltage". Perhaps because this is rigourous analysis.

Rob Eagle:

. . .

Volt drop - volt drop limits, for installations, are defined in 7671, other than that it depends upon the equipment itself and its tolerance to voltage fluctuations, switch-mode power supplies, for example, generally work anywhere in between 90 - 260V so fairly tolerant to volt drop at 230V, other things may not be so, i.e. lamps. 

Now we are getting somewhere! Fluctuation in supply pressure, as compared with drop of potential along a conductor. Not the same thing. We need to be sure what we are talking about. I agree that in this case we need a simple term to describe what is happening. "Electro-motive force deviation" is too ponderous a term. If we need to quantify this, there is surely no harm in stating the quantifying unit?


I do maintain that my physics teacher was right in discouraging the term "volt drop" in analysis of an electrical network, even though the penalty may have been a bit heavy. I discouraged it myself in my lecturing days. Students using the expression in an ambiguous way tended to lose the plot.


One problem is that some basic units of measurement have no formal definition; we must use some inadequate synonym, e.g. "electrical pressure" for electro-motive force. Hence the customary usage of simple terms like "voltage". It does no harm where we need no rigourous analysis. "Potential" is of course a word with a broader meaning - "capability of achievement".  


It is interesting to note that in devices like motors, transformers, etc., engineers sometimes use the term "back e.m.f." rather than "back voltage". Perhaps because this is rigourous analysis.