Voltage differential of more than 1 volt (plus
in the 0-32 dc volt output of the variable ex-
ternal volts circuit.
o r minus) between any two settings indicates
unbalanced phase conditions (par. 17).
d. Dc Variable Volts Negative and Positive
B i n d i n g Posts. The dc variable volts negative
and positive binding posts (28-C) are a
(Designated as VARIABLE VOLTS, ON-
threaded two-piece post which can be threaded
OFF FUSE, DC VARIABLE VOLTS)
apart to receive a test lead terminal and tight-
ened to hold the terminal secure. The binding
a. General. The variable volts circuit consists
posts will also receive a plug-in type terminal
of four units, which are located on an instru-
which can be inserted in a ferrule in the top of
ment panel (28) on the upper right hand end
t h e post. The posts are used to connect the
of the main control panel. The units are used
variable external volts circuit to the units un-
f o r the testing of relay pick-up and drop-out
dergoing test by means of two test leads.
v o l t a g e of generator regulators and generator
control boxes, and provide a variable dc voltage
c i r c u i t with an external output from 0 to 32
Positive Binding Posts (Designated as
volts which is indicated on the dc voltmeter (5)
EXTERNAL DC VOLTMETER)
when the circuit is in operation. The circuit is
The external dc voltmeter negative and posi-
protected for overload by a 15-ampere fuse, c
tive binding posts (29), located on the center
below a circuit breaker (49), and is available
right hand end of the main control panel, are a
w i t h or without the varidrive assembly oper-
threaded two-piece post as described in para-
ating (par. 43) and is independent of the bat-
t e r i e s within the test stand. The dc voltmeter
t o r switch (23) is set in the "EXT VOLTS"
circuit selector switch (23) and the dc variable
position and by using a set of test leads con-
power supply control (48) are used in conjunc-
nected to the two binding posts, a external dc
tion with this circuit and are described in para-
v o l t a g e source independent of the test stand
can be measured which will be indicated on the
graphs for further information on operation of
d c voltmeter (5).
t h e variable external volts circuit. The four
units of this circuit and their description and
function are given in b through d b e l o w .
(Designated as TEST INDICATOR)
b . Variable Volts On-Off Switch. The vari-
a. General. The test indicator circuit con-
able volts on-off switch (28-A) is a two-posi-
s i s t s of three units which are located on an
tion, single-pole, single-throw, 25-ampere, 30-
instrument panel (30) on the lower right hand
volt, dc, toggle switch used to control the output
end of the main control panel. The units of the
of the variable external volts circuit. When the
circuit are used for visually checking the open-
switch is in the "ON" position it connects a 0
ing and closing of the contact points of indi-
to 32 volts output to the dc variable external
volts negative and positive binding posts
erator control boxes. The circuit can be used
(28-C). Always place this switch in the "OFF"
in voltage ranges of 6, 12, or 24 volts and is
position when the circuit is not in use.
connected in series with unit undergoing test.
The circuit can also be used without the vari-
c. Variable Volts Circuit Fuse Holder. T h e
d r i v e operating where a method is needed to
v a r i a b l e volts circuit fuse holder (28-B) con-
check the continuity of a circuit, etc. (par. 43).
t a i n s a 15-ampere fuse which is held in the
The three units of this circuit and their descrip-
holder by a threaded cap. To remove the fuse
tion and function are given in b and c b e l o w .
f o r inspection or replacement turn the cap to
b . Test Indicator Lamp. The test indicator
the left until free. The fuse is held in the cap
lamp (30-A) consists of a 6-8-volt bulb with a
by a friction fit sleeve and can be removed by
red torpedo lens. It is connected in series with
firmly gripping it and pulling outward on the
fuse. The fuse provides an overload protection
a relay so that a visual indication is given for
