Page 119 - Louth Transformer Catalogue

LT DATA

SHORT CIRCUIT CURRENT
The short circuit current that a winding can deliver is given by the following formula.

ISC = IFL x 100
Vz
IFL = Designed winding current
Vz = Impedance voltage of that winding (%)

It must be remembered that the short circuit current derived from the above equation presumes the maintenance
of the full line voltage under fault conditions. But in fact the line voltage is generally maintained for the first few
cycles only after the first instant short circuit. Only larger systems being capable of supplying sufficient MVA will
maintain the supply voltage behind the fault. Therefore, obviously as the supply voltage drops so will the value of
the short circuit current.

MAINS TRANSFORMERS
1) All primaries suitable for 50/60Hz operation.
2) All secondary voltages stated are at maximum load.
Please indicate on your order if off load voltages are required.
3) Flash tested at 4.0KV r.m.s
4) All temperature limits within Cee 15 at 25°C ambient at full load.

REGULATION

Regulation is determined by the following formula:-

Off load voltage - Full load voltage
Off load voltage

EFFECT OF AMBIENT TEMPERATURE ON RATINGS

AVERAGE PEAK SUGGESTED RATING REDUCTION
30°C 35°C NIL
35°C 45°C 6%
40°C 50°C 12%
45°C 55°C 20%

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