Elliott Sound Products |
Transformers - Part 3 |

Field descriptions for TRAFO7 Excel spreadsheet ...

Field | Type | Description |

Ud | Input | Si diode voltage at high current (change this voltage for using valve (tube) rectifiers, or special diodes) |

Ubrss | Input | max. allowed typical peak-peak ripple voltage |

Ia | Input | desired nom. DC output current per coil (ohmic load) |

alpha | Input | current form factor (RMS > average!) 1.5 ... 2 |

Uaminn | Input | desired minimum nominal output voltage, to remember your goal |

Uamin | Input | minimum nominal output voltage for computation |

rho | constant | Copper thermal specific resistance |

L | Input | line length from house mains entry to transformer,one way (metres) |

A | Input | wire cross section area of this line with length L |

Rk | computed | resulting line resistance for both ways |

Unetz | Input | nominal effective mains voltage |

fn | Input | mains frequency |

tolup | Input | upper limit of mains voltage variation |

tolow | input | lower limit of mains voltage variation |

ü | computed | transformation ratio |

ü2 | computed | impedance transformation ratio |

Rks | computed | line resistance transformed to secondary, usually very small |

f | Input | actual used transformer loss factor |

f | computed | heuristical determined loss factor, no large difference with actually used, unless reason for this is known! |

U0eff | computed | nominal sine AC effective transformer voltage per coil with no load |

Ineff | computed | nominal sine AC effective transformer current per coil |

In | computed | nominal sine AC transformer peak current per coil, compare with Imax for a hint for alpha (value is doubled in case of Center circuit, since only one coil at a time is conducting in this rectifier circuit, while both are conducting with pure resistive load) |

Imax | computed | secondary peak current per coil, also current through diodes, compare with In to avoid core saturation |

Idm | computed | average diode current |

Pa | computed | total power per winding delivered to load resistor |

Pn | computed | total transformer power, including rectifier power, load power, all coils and factor alpha |

Pns | computed | Pn divided by number of coils (1, 2) |

Ua0+ | computed | idle voltage on capacitor, including mains upper Ua0+ tolerance |

Ua0 | computed | idle voltage on capacitor, nominal mains |

Ua0- | computed | idle voltage on capacitor, including mains lower tolerance |

Usper+ | computed | idle voltage stress on diodes, including mains upper usper+ tolerance |

Ua8+ | computed | infinite capacitor voltage with load and mains upper Ua8+ tolerance, can be used to estimate e.g. amplifier losses |

Ua- | computed | capacitor voltage (capacitance value Cl), including mains lower tolerance and line losses and ripple, lowest instantaneous value |

Ua8 | computed | infinite capacitor voltage with load, nominal |

Ua8ber | computed | tryed infinite capacitor voltage with load |

r | computed | ratio between Ua8 and Ua8ber in %, error of iteration, minimise to 0.0! |

Uneff | iteration input | nominal effective transformer secondary voltage, this value must be iterated to minimise r |

Rv | computed | load resistor that would draw Ia with infinite capacitor |

Ri | computed | transformer resistance for each coil |

Ri+main | computed | effective transformer resistance for each coil, including line losses |

Cl | computed | capacitor size for give ripple, frequency, load |

Pd | computed | power loss per diode |

Pg | computed | total power loss, sum for all diodes |