Phase Locked Loop; Phase Loss; Table 6 - Low Supply Line Voltage - York SSS 7L-B Operation Manual

FORM 160.00-O2
ISSUE DATE: 04/30/2019
shutdown will occur. This shutdown is disabled for the
first 20 seconds of the starter run, to prevent nuisance
shutdowns from heavily loaded transformers. The
voltage range is programmed on the OptiView Control
Center. If no voltage range is programmed, then this
shutdown will be disabled (ASSOCIATED LITERA-
TURE listed on Page 3).
The shutdown message displayed will be "LCSSS -
LOW SUPPLY LINE VOLTAGE".
Possible Problems
• Verify that the proper voltage range is selected on
the OptiView Control Center.
• Verify proper line voltage is being applied to the
starter.
• If the problem occurs during generator operation,
add some standby load to the generator so that
the generator can respond more quickly to load
changes.

PHASE LOCKED LOOP

The cathode connection of the negative SCRs is con-
nected to the 3-phase AC power line. This informa-
tion is sent to the Logic/Trigger Board, where a circuit
generates a waveform that is synchronized to the 'A'
phase voltage. This waveform and the 'A' phase volt-
age are compared, and the deviation is used to generate
an error signal. The error signal is then used to correct
the waveform and maintain synchronization with the
'A' phase voltage. The synchronized waveform is used
for the firing control of all the SCRs. If the error sig-
nal becomes too large then the synchronization with
the 'A' phase voltage will be lost. If synchronization
is not maintained, the SCRs will misfire and damage
the chiller.
The shutdown message displayed will be "LCSSS -
PHASE LOCKED LOOP".

TABLE 6 - LOW SUPPLY LINE VOLTAGE

VOLTAGE RANGE
Disabled
200 - 208
220 - 240
380
400
415
440 - 480
550 - 600
JOHNSON CONTROLS
Possible Problems
• Although this circuit is very fast, storms or power
problems can cause the frequency of the 'A' phase
voltage to change too rapidly.
• If the problem occurs during generator operation,
ensure that the JP1 jumper has been cut (on Rev
C. or earlier Logic/Trigger Boards).
• If the problem occurs during generator operation,
add some standby load to the generator so that the
generator responds more quickly to load changes.

PHASE LOSS

The three phases of input line voltage are fed back
to the Logic/Trigger Board via the cathode connec-
tions of the negative SCRs. The RMS voltage is then
compared against a threshold value, that is 30% of the
programmed input voltage range. For example, if the
programmed input voltage range is 440-480 VAC, then
the threshold value will be 132 VAC. If the voltage
range is disabled in the OptiView Control Center then
the shutdown value will be 30% of 200 VAC. Thus,
the threshold value will be 60 VAC. Anytime one of
the three phases of input line voltage drops below the
threshold value, a Cycling shutdown will occur.
The shutdown message displayed will be "LCSSS -
PHASE LOSS".
HIGH SUPPLY LIMIT – STOPPED
None
174
200
331
349
362
400
502
SECTION 5 – CYCLING SHUTDOWNS
HIGH SUPPLY LIMIT – RUNNING
None
160
185
305
320
335
370
460
5
27