Recent content by Physicist3

Hi, I am trying to get up to speed on electrical schematics and how to read them and I am getting stuck with a particular symbol. I understand that the following symbol represents a link; However, I cannot seem to find what the following one means? I believe that it is meant to represent...

When Plotting relay current curves using log paper, I understand that all curves should be plotted on a common base voltage (converting currents accordingly) and the curves can be cut at the maximum fault current level that the device is likely to see (corrected to the base current). What I...

Hi, apologies if this is very simple but I am still learning the basics of power system analysis and would like it if someone would be able to clarify what I have been told regarding system fault levels and subsequent system reactance values (X) from this. Basically, I have been told that...

Hi jim, many thanks for the reply and your advice :). Considering the following theoretical example, and based upon what you have said, does this look about right: Motor A: Drawing 55A, PF = 0.88 Motor B: Drawing 62A, PF = 0.79 Motor C: Drawing 87A, PF = 0.82 Motor A: Φ = cos-1(0.88) =...

Hi Suppose I have three motors connected to a single busbar which is fed by a single transformer and suppose that the current into the busbar (i.e. the total current of the transformer secondary) is known. If I wish to calculate the transformer voltage drop the I will obviously need the load...

Hi, If the voltage, full load current and full load output power (kW) of a 3 phase induction motor are known, and the efficiency is assumed to be 90% (is this realistic), am I correct in thinking that the full load power factor can be approximated (due to assumed and not actual efficiency) as...

Hi, I need to calculate the voltage regulation of the 3 ph Dzn transformer. I have knowledge of the current going into the primary winding of the transformer (Delta winding) and hence need to calculate the current in the secondary (load current) so that I can use this in the voltage...

Hi, I understand that an exciton must reach the D/A interface within the Exciton diffusion length to prevent recombination, however, what are the factors during device fabrication that can affect the Exciton diffusion length of a P3HT:PCBM BHJ OSC?

For a full wave thyristor controlled rectifier, if the firing occurs at 90°, the average output voltage is zero. Therefore the average output current will be zero also I assume? If considering idealised current waveforms, should all the currents also be zero (thryristors etc.) be zero or...

hi, On a diode datsheet, is the value quoted as the forward voltage the same as the cut-in voltage?

Homework Statement For a bridge rectifier (4 thyristor) feeding an RL load having infinite inductance (to assume constant current) and a 100 ohm resistance, calculate for firing angles of 90°, 120° & 150° the average DC voltage and current. The bridge supply is 200V RMS. Draw Waveforms of...

Hi, many thanks for the reply. I understand that this is the case for a full sine wave, but in the case of a rectifier where the wave is not complete, surely the value of the RMS current will not stay as sqrt(2)?

If the inductance is considered as high enough to produce a constant ripple free current, am I correct in thinking that the RMS current will simply be the same as the Mean DC current value, worked out by dividing the average dc voltage value by the circuit resistance for an RL Load?

Hi, For a single phase full wave fully controlled bridge rectifier carrying a RL load, how is the RMS voltage and current calculated? I have researched textbooks but can only seem to find RMS equations for Resistive loads and I am not sure whether the negative load voltage will affect the...

Hi, I am trying to model a full wave single phase thyristor controlled rectifier feeding a resistor and capacitor in parallel (like a power supply I believe where the capacitor is used for smoothing?) and I would like to calculate the average output dc voltage in a similar fashion as for a...