Formulae | gunsparky

Browse the glossary using this index

Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ALL

E

Efficiency

$E f f percent sign equals fraction numerator O u t p u t cross times 100 over denominator I n p u t end fraction$

$E f f percent sign space equals fraction numerator P subscript i n end subscript space minus space L o s s e s over denominator P subscript o u t end subscript space end fraction cross times 100$

I

Impedance percentage

$Z percent sign space equals fraction numerator space V subscript I m p e d a n c e end subscript over denominator V subscript R a t e d end subscript end fraction cross times space 100$

P

Percentage Impedance

$Z percent sign space equals fraction numerator space V subscript I m p e d a n c e end subscript over denominator V subscript R a t e d end subscript end fraction cross times space 100$

Power

$P equals fraction numerator 2 straight pi nT over denominator 60 end fraction$

$P equals square root of 3 V I space cos empty set$

R

Regulation %

$V subscript r e g end subscript percent sign equals fraction numerator left parenthesis V subscript N L end subscript minus V subscript F L end subscript right parenthesis over denominator V subscript N L end subscript end fraction cross times 100$

Rotor frequency

$f subscript r equals fraction numerator S l i p percent sign cross times f subscript s u p p l y end subscript over denominator 100 end fraction$

The rotor frequency is equal to the supply frequency times the slip percentage divided by 100

S

Start Current

Autotransformer $I subscript m o t o r space s t a r t end subscript equals fraction numerator percent sign T A P over denominator 100 end fraction cross times I subscript d o l end subscript$

Autotransformer $I subscript L i n e space s t a r t end subscript equals open parentheses fraction numerator percent sign T A P over denominator 100 end fraction close parentheses squared cross times I subscript d o l end subscript$

Star Delta $I subscript s t a r end subscript equals 1 third cross times I subscript d e l t a end subscript$

Starting Torque

Autotransformer $T subscript s t a r t end subscript equals open parentheses V subscript s t end subscript over V subscript d o l end subscript close parentheses squared cross times T subscript d o l end subscript$

Star Delta $T subscript s t end subscript equals 1 third cross times T subscript d o l end subscript$

Synchronous Speed

$N subscript s y n c end subscript equals fraction numerator 120 f over denominator P end fraction$

T

Transformer ratios

$N subscript 2 over N subscript 1 equals V subscript 1 over V subscript 2 equals I subscript 2 over I subscript 1$

$V subscript 1 space I subscript 1 space equals space V subscript 2 space I subscript 2$

$N subscript 1 space I subscript 1 space equals space N subscript 2 space I subscript 2$

$V subscript 1 over V subscript 2 equals N subscript 1 over N subscript 2$

How can there be so many formulae for the same thing? There isn't. The second two are just simpler transpositions of the first one.