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Current Mod ule (CM-2)
On applications where the Compressor Motor is con-
trolled by an Electro-Mechanical Starter, the OptiView
Control Center is equipped with a Current Module. The
Cur rent Mod ule pro vides com pres sor motor Over load
and Power Fault protection. The Current Mod ule also
pro vides an an a log voltage representing the com pres sor
motor cur rent to the Microboard for dis play and Cur-
rent Limit control. While the chill er is run ning, the
Microboard controls the Pre-rotation Vane (PRV) po-
si tion to limit the motor current to the system 100% Full
Load Amp (FLA) value.
The contacts of Current Module K1 relay (identifi ed as
"CM" contacts on the OptiView Control Center wiring
diagram) are interfaced into the Motor Controller ini-
ti at ed shut down circuit that is located between OptiView
Control Center TB6-53 and I/O Board TB1-16 (ref. Fig
17 and 37). They are also connected as a digital input
to I/O Board J2-1. Relay K1 is normally en er gized,
main tain ing its con tacts in a closed position. When ev er
the Current Module ini tiates a chiller shutdown, it de-
en er giz es K1, opening its contacts. This interrupts the
cir cuit to I/O Expansion Board RUN relay coil 1R (K18),
de-en er giz ing it and causing the Starter to shut down.
Si mul ta neous ly, the Microboard reads the open ing of
these contacts via I/O Board J2-1, initiates a SYSTEM
COASTDOWN and dis plays the ap pro pri ate mes sage
as described below.
Three Current Transformers in the Com pres sor Mo-
tor Ter mi nal Box (ref Fig. 38) provide 3 phase motor
cur rent sig nals to the Diode Bridge (DB). The re quired
turns ra tio of the Current Transformers is de ter mined
by the sys tem 100% FLA. The Diode Bridge rectifi es
and com bines the three signals into one DC signal that
is applied to the parallel Variable Resistors (RES).
These are Factory adjusted (fi eld adjusted on service
re place ments) to provide a nominal 1.0VDC (0.15 to
1.10VDC) signal to the Current Module at J1-1 and J1-2
when the com pres sor motor current is at 100% FLA. Fig.
38 con tains a formula to calculate the re sis tance of RES
re quired to achieve 1.0VDC at 100%FLA. The 100%
FLA value is located on a label adhered to the inside of
the OptiView Control Center door.
64
SECTION 10
CURRENT MODULE (CM-2)
(REFER TO FIG 36 - 38)
The motor current signal input at J1-1 & J1-2 is ap plied
to potentiometer R8. This is Factory adjusted (fi eld ad-
just ed on service replacements) to illuminate the 105%
CURR indicator (CR6) when the com pres sor motor
current reaches 105% FLA. This calibrated volt age is
applied to the Power Fault detector, Overload de tec tors
and Multiplexer (MUX).
The Power Fault circuit protects the compressor
mo tor and driv e line from transient torque damage. It
an tic i pates the transient torque condition by detecting
a mo men tary in ter rup tion in motor current and de-
en er giz ing the start er before damage can occur. If the
chill er has been run ning for >75 seconds and the motor
cur rent decreases to <10% FLA, a Power Fault shut-
down is ini ti at ed. The Power Fault indicator (CR5) is
il lu mi nat ed and remains illuminated until man u al ly re set
with RE SET switch S2. Relay K1 is de-en er gized for 1
sec ond and then returned to the energized state. Re lay K1
con tacts (CM) open for 1 second and then re turn to the
closed state. A SYSTEM COASTDOWN is ini ti at ed
and POWER FAULT is displayed on the Dis play. The
chiller will automatically restart upon com ple tion of
SYSTEM COASTDOWN.
If the motor current remains continuously at >105%
FLA for 50 seconds (Nominal), an OVERLOAD
shut down is ini ti at ed. The Overload indicator (CR4)
is il lu mi nat ed and re mains illuminated until manually
reset with RE SET switch S2. Relay K1 is de-en er gized,
open ing K1 con tacts (CM). Relay K1 remains de-ener-
gized until man u al ly reset with RESET switch S2. A
SYS TEM COASTDOWN is initiated and MOTOR
CON TROL LER-CON TACTS OPEN is displayed.
The chiller cannot be start ed until RESET switch S2 is
man u al ly pressed.
If the motor current remains continuously at 245% FLA
for 40 seconds, 290% FLA for 20 seconds or 360%
FLA for 10 seconds, an OVERLOAD shut down is ini-
ti at ed. Relay K1 and Overload indicator CR4 op er ate
as de scribed immediately above. A SYSTEM COAST-
DOWN is initiated and MOTOR CON TROL LER -
CON TACTS OPEN is displayed. The chiller cannot
FORM 160.54-M1(503)
YORK INTERNATIONAL
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