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Hi Dan Thanks for your reply It is appreciated. Yes you are correct the phase angle error is very small in most measuring CTs and should be only a few minutes. I need some help if possible with the equations used in calculating the ratio and phase angle errors in measuring CTs as all the...

Is there anyone that can help me as I really could do with some assistance? Cheers Ray

Is there anyone that can help me as I really could do with some assistance? Cheers Ray

Can anyone help me with the accurate calculation of ratio and phase errors in measuring current transformers? I would like to get a spreadsheet or something similar together for the design of toroidal bushing transformers and so far have not come up with any equations or methods that agree with...

Can anyone help me with the accurate calculation of ratio and phase errors in measuring current transformers? I would like to get a spreadsheet or something similar together for the design of toroidal bushing transformers and so far have not come up with any equations or methods that agree with...

Just wanted to say thanks to both SparksAlot and ScottyUK for your invaluable help with this information and for the time you both spent helping me out. It is much appreciated and I owe you both a drink!! Cheers Ray

Hi SparksAlot Thanks my friend. From this am I right in saying that as the temperature goes up the core restivity increases and so the eddy currents reduce? Also what does the 0.00065 refer to? Cheers Ray

Hi Sparks Alot I think I have got most of it down, just a couple of questions. 1. How did you get to CORE = 23.7688+ from the measured was 24.7W? 2. The stray loss is 2.2163 WATTS @ 22deg.C and reduces due to the rise in resistance with temperature to 2.2163/k =1.8076W at 80deg.C is this...

Thats a good point, Is there no send facility via the forum as they have our addresses? Cheers buddy Ray

Hi SparkAlot Thanks for that my friend your effort is very much appreciated. I will have a good go with this. Your spreadsheet will be much appreciated if you would be so kind! Cheers Ray

...came to the following using: Rated current @ 230v and 960VA = 960/230= 4.173 A Ratio up test voltage at rated current = (4.173A/2.188A)* 3.55V = 6.772V Ratio up tested wattage = 7.51 * (4.173A/2.188A)^2 = 27.329W But how did you come up with the percentages...

Thanks SparksAlot If you could help me on this I would be eternally gratefull! OK here goes... all are measured values Hv (pri) resistance @ 22deg.C = 0.4978R Lv (sec) resistance as above = 0.0116R Voltage ratio Pri: 230v Sec: 25.5V = ratio 9.109 (24v rated on load at 40A or 960VA No-Load...

Hi Scotty Yes I agree with what your saying and this is almost definately the case the location is rural and +10% over volts is a regular occurrence for them apparantly, the iron saturation and hence the peaky input current is causing the issue, but there are other factors and that is why I...

...I always thought that the measured impedance voltage Ez = 3.55v was used to find the percentage impedance by Impedance volts / rated input volts * 100 as a % I am not sure why they didn't just measure the voltage at 100% of the current as the transformer is only small. I assumed then that...

...of rated current (although I cannot get it to add up) and then the reactance Ex = 0.51 derived from Sqr(Ez 3.87^2 - Er 3.84^2) and Er = 36.84W * 10 /960VA as usual, but I cant get it to add up. Or is the Ex = 0.51 calculated and then added in quadrature to come up with the Ez = 3.87%...

Hi everyone Many thanks for all your replies. I was not originally concerned with inrush current (I am however very keen on learning a little more about this...) My main concern was just calculating with reasonable accuracy the no load rms current of transformers/coils wound on a particular...

...current at high flux densitites can be obtained from the pk H curves. If the mag current were sinusoidal then I could use (Hpk (from curves) * 0.707 * Magnetic path length)/turns But as the mag current waveform would be peaky at high flux densities I would have no way of knowing the pk/rms...

Dear Experts Can anyone tell me how I can calculate the rms magnetizing current of a transformer when the only information I have for the core steel are curves for Watts Loss per Kg and Peak Magentic Field strength(A/meter) for any given value of flux density. As far as I can see, using the...

Thanks Stevenal OK I understand how you came to 3.69% regulation and R=(54.09/1440)% and Z is the quadrature sum of R+X, but how did you come up with X and 53.2VArs? Will this then evaluate to COS(ATAN(53.2/(1440+54.09+6.5)))= 0.99937 = 1 ? Cheers Ray

...first on core. PRIMARY WINDING DATA. ~~~~~~~~~~~~~~~~~~~~~ Pri 1. Volts, Amps, DCR.*, Cu kg. 115, 6.57, 0.288, 0.577 Pri 2. Volts, Amps, DCR.*, Cu kg. 115, 6.57, 0.303, 0.607 Pri/Sec insulation 3 layers. 13 mm. Polyester, 50%...