KEPCO JQE 150-1.5MVPY-26956 Half Rack - Manual (Page 29)

JQE SPECIAL SVC 081111 3-5
3.4.2 EQUATIONS SHOWING THE OPERATION OF THE KEPCO BRIDGE
The following relationships govern the operation of the Kepco Bridge at balance in voltage
mode, i.e., with VAA’ = 0.
(1)
(2)
(3)
The ratio of Ohms control - resistance needed per volt output is termed the “CONTROL RATIO.“
It is 1000 Ohms/Volt for remote resistive control only. For local control the ratio is determined by
the front panel VOLTAGE control potentiometer value and tolerance.
As can be seen from equation (1), the output voltage E
O
can be controlled by varying any one of
the three quantities. Rewriting equation (1) we have
The ration constitutes the bridge control current I
b
(Eq. (2).
Therefore we can write E
O
= I
b
R
VC
(Eq. (3).
Making I
b
a precision quantity establishes a precise programming ratio, so that the accuracy of
E
O
is solely dependent upon R
VC.
This mode of operation is referred to as Resistance Program-
ming and is covered in detail in PAR. 3.6.
NOTE: For all programming and adjustment components, use high quality, wire-wound resis-
tors with a T.C. of 20 p.p.m or better.
Similar relationships can be described for operation in Current Limit mode. The following rela-
tionships govern the operation of the Kepco Bridge at balance in current mode, i.e., with VAA’ =
0.
(4)
(5)
(6)
(7)
EO
Er
--------
RVC
Rr
------------ =
Er
Rr
------ Ib =
EO IbRVC =
Where: E
O
= Output Voltage
E
r
= Reference Voltage
R
r
= Reference Resistance
R
VC
= Voltage Control Resistance
I
b
= Bridge Control Current
EO
Er
Rr
------ RVC × =
Er
Rr
------
IORSKS
Er
----------------------
RCF
Rr
----------- =
IO
RCF
KSRSRr
---------------------- Er =
IO
RCF
KSRS
---------------
Er
Rr
------ =
Where: E
O
= Output Voltage
E
r
= Reference Voltage
R
r
= Reference Resistance
I
b
= Bridge or Control Current
K
S
= Current Sensing Amplification Factor
R
S
= Current Sensing Resistor
R
CF
= Current Feedback Resistor
IO
RCF
KSRS
--------------- Ib =