﻿142 
  Dr. 
  Drysdale 
  on 
  the 
  Use 
  of 
  Shunts 
  and 
  Iransformers 
  

  

  and 
  yjr 
  will 
  then 
  be 
  the 
  maximum 
  error 
  in 
  the 
  power 
  factor 
  

   for 
  loads 
  nearly 
  in 
  quadrature. 
  Consequently, 
  iu 
  the 
  above 
  

   case, 
  if 
  the 
  error 
  in 
  the 
  power 
  factor 
  is 
  not 
  to 
  exceed 
  '01, 
  

  

  AT 
  10(l--785 
  2 
  ) 
  A1 
  OAK 
  , 
  

  

  — 
  r=?r 
  ^ 
  — 
  _ 
  - 
  — 
  ^x 
  , 
  01 
  = 
  , 
  00o42 
  or 
  "54 
  per 
  cent. 
  : 
  

  

  and 
  we 
  saw 
  before 
  that 
  for 
  the 
  ratio 
  to 
  be 
  correct 
  to 
  1 
  per 
  cent. 
  

  

  AT 
  

  

  -— 
  = 
  l*o3 
  per 
  cent. 
  

  

  Transformers. 
  

  

  In 
  dealing 
  with 
  the 
  application 
  of 
  transformers 
  to 
  instru- 
  

   ments, 
  we 
  shall 
  have 
  to 
  consider 
  separately 
  their 
  employment 
  

   as 
  " 
  current 
  transformers 
  " 
  or 
  as 
  " 
  voltage 
  transformers"; 
  the 
  

   former 
  being 
  employed 
  in 
  conjunction 
  with 
  ammeters 
  for 
  the 
  

   purpose 
  of 
  utilizing 
  instruments 
  of 
  convenient 
  range, 
  and 
  to 
  

   insulate 
  the 
  instrument 
  from 
  hi 
  oh 
  voltage 
  circuits 
  ; 
  the 
  latter 
  

   with 
  electromagnetic 
  or 
  hot-wire 
  voltmeters 
  to 
  avoid 
  undue 
  

   waste 
  of 
  energy, 
  and 
  again 
  as 
  with 
  ammeters 
  to 
  disconnect 
  

   them 
  from 
  the 
  high-pressure 
  circuits. 
  In 
  wattmeters 
  and 
  

   energy-meters 
  of 
  the 
  induction 
  type, 
  transformers 
  are 
  fre- 
  

   quently 
  employed 
  in 
  both 
  the 
  main 
  and 
  shunt 
  circuits 
  

   simultaneously. 
  

  

  The 
  relations 
  between 
  the 
  primary 
  and 
  secondary 
  currents 
  

   and 
  voltages 
  have 
  been 
  obtained 
  by 
  Steinmetz 
  and 
  others 
  

   from 
  the 
  well-known 
  vector 
  diagram, 
  but 
  it 
  will 
  be 
  well 
  to 
  

   treat 
  the 
  problem 
  ab 
  initio 
  as 
  we 
  require 
  the 
  results 
  to 
  be 
  

   exhibited 
  in 
  the 
  most 
  convenient 
  form. 
  

  

  Current 
  Transformers. 
  — 
  It 
  is 
  most 
  convenient 
  to 
  deal 
  at 
  

   first 
  with 
  the 
  magnitudes 
  and 
  phase 
  relations 
  of 
  the 
  currents, 
  

   and 
  we 
  can 
  afterwards 
  apply 
  the 
  results 
  to 
  the 
  investigation 
  

   of 
  the 
  voltage 
  relations. 
  

  

  Let 
  A 
  p 
  = 
  primary 
  ampere 
  turns 
  = 
  C 
  p 
  n 
  p 
  . 
  

  

  A 
  s 
  = 
  secondary 
  „ 
  „ 
  =C 
  n 
  s 
  . 
  

  

  Am 
  = 
  magnetizing 
  „ 
  „ 
  = 
  C 
  m 
  n 
  p 
  . 
  

  

  A 
  c 
  = 
  core 
  loss 
  „ 
  „ 
  =C 
  c 
  n 
  p 
  . 
  

  

  A 
  = 
  no 
  load 
  ,, 
  „ 
  = 
  C 
  n 
  p 
  . 
  

  

  <\> 
  p 
  = 
  lag 
  of 
  primary 
  current 
  behind 
  core 
  E.M.F. 
  

  

  (j) 
  s 
  = 
  lag 
  of 
  secondary 
  „ 
  „ 
  ., 
  „ 
  

  

  a 
  = 
  lag 
  of 
  no 
  load 
  „ 
  „ 
  ., 
  „ 
  

  

  yjr 
  = 
  phase 
  displacement 
  between 
  primary 
  and 
  

  

  secondary 
  currents. 
  

  

  