Currents,  Three  Phase Triphased

currents.  (See  Appendix — Currents,  Tri-
phased, Alternating.)

Currents,    Triphased,    Alternating

— Three  alternating  currents  differing
1 20°  in  phase  from  each  other.
In  the  two-phase  system  two  currents  differ-
ing in  phase  90°  have  a  common  return  wire
whose  area  should  be  V  2  greater  than  either
leading  wire.
In  the  three-phase  system  each  of  three
currents  differing  in  phase  120°  uses  alter-
nately one  or  two  of  the  three  wires  for  a
return.
Curve,     Arrival  of   Telegraph    Circuit

A  curve  of  ordinates  and  abscissas

which  represent  respectively  the  times  and
the  gradual  increase  of  current  at  the  re-
ceiving end  of  a  telegraph  circuit  from  the
time  the  circuit  is  closed  until  the  time
the  current  has  reached  its  full  strength.
Curve,  Clown's  Hat A  term  pro-
posed for  the  curve  of  a  current  or
electromotive  force  in  which  the  pressure
generated  increases  or  decreases  at  a
maximum  rate  of  change,

The  name  is  taken  from  the  shape  of  the
curve  being  somewhat  similar  to  the  shape  of  a
peaked  or  clown's  hat.
Curve,  Top-Hat A  term  proposed

for  the  current  or  E.  M.  F.  in  which  the
pressure  generated  is  fairly  constant  for  a
considerable  time  at  its  maximum  rise
and  fall.
The  name  is  taken  from  the  shape  of  the
curve  being  somewhat  similar  to  that  of  a
top-hat,  or  flat  crowned  hat.  A  current  for
the  primary  of  a  transformer  «r  induction


Cut.]


593


[Dec.
coil,  however,  of  the  top-hat  type,  makes  a
bad  form  of  secondary  current  curve,  for  in
such  a  curve  the  rate  of  change,  whether
increasing  or  decreasing,  would  be  small.
The  current  whose  curve  of  electromotive
force  is  sharp  and  peaked  like  a  clown's  hat
would,  of  course,  be  preferable.
