Formulae for Rotating Machines

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

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

P

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 %

$R e g percent sign equals fraction numerator N subscript s y n c end subscript minus N space over denominator N subscript s y n c end subscript end fraction cross times 100$

$V subscript r e g end subscript percent sign equals fraction numerator open parentheses V subscript N L end subscript minus V subscript F L end subscript close parentheses over denominator V subscript F L end subscript end fraction cross times 100$

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

I know what your thinking. WHICH ONE IS IT. The answer is that it depends. Some manufacturers use different numbers to make their machines look better. Your guess is as good as mine. Not very helpful I know but it shouldn't matter that much.

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

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