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Student & Learning Zone - City & Guilds
Help with formula please.
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<blockquote data-quote="allan.vaughan4" data-source="post: 408937" data-attributes="member: 27070"><p>Hi All,</p><p></p><p>I am trying to understand the formula Ze x Ia is less than or equal to Uo x Cmin.</p><p></p><p>I need to identify Ia. (Value in amps causing operation of protective device).</p><p></p><p>I believe you use ohms law. (I = V / R) . V being either 230 V / 400 V.</p><p></p><p>i am struggling to identify where you get the resistance figure from, I have carried out calculations using Ze as the figure for R but this does not work in the equation as you end up with 230 V or 400 V Less than or equal to Uo x Cmin (218.5 V).</p><p></p><p>So the figures I have pulled up are say Ze = 25 Ohms. V is 230 OR 400. And I have been using R as the Ze figure again = 25 Ohms. This is obviously where I am going wrong.</p><p></p><p>Can anybody explain where the proper place to get R is from please?</p><p></p><p>Your help in this matter would be very much appreciated!!</p><p></p><p>Many thanks,</p><p></p><p>Allan.</p></blockquote><p></p>
[QUOTE="allan.vaughan4, post: 408937, member: 27070"] Hi All, I am trying to understand the formula Ze x Ia is less than or equal to Uo x Cmin. I need to identify Ia. (Value in amps causing operation of protective device). I believe you use ohms law. (I = V / R) . V being either 230 V / 400 V. i am struggling to identify where you get the resistance figure from, I have carried out calculations using Ze as the figure for R but this does not work in the equation as you end up with 230 V or 400 V Less than or equal to Uo x Cmin (218.5 V). So the figures I have pulled up are say Ze = 25 Ohms. V is 230 OR 400. And I have been using R as the Ze figure again = 25 Ohms. This is obviously where I am going wrong. Can anybody explain where the proper place to get R is from please? Your help in this matter would be very much appreciated!! Many thanks, Allan. [/QUOTE]
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Student & Learning Zone - City & Guilds
Help with formula please.
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