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Operating Instructions
31
Alarms - Upon occurrence of any of the following alarms, the alarm message appears on the LCD dis-
play, the Alarm Present/Silence switch is illuminated, and the audible alarm is activated. Pressing
the “Alarm Present/Silence” switch silences the audible alarm. After the alarm condition is corrected,
the alarm can be reset by pressing the “Alarm Present/Silence” switch when prompted by the LCD
display or by way of any Central Monitoring System.
• Output Overvoltage - Indicates one or more of the output phase voltages has exceeded the pre-
set limit (normally +6% of nominal). The high output voltage should be verified and corrective
action taken. In the absence of other procedures, a normal (orderly) system shutdown should be
performed to prevent load equipment damage.
• Output Undervoltage - Indicates one or more of the output phase voltages has exceeded the
preset limit (normally -13% of nominal). The low output voltage should be verified and corrective
action taken. In the absence of other procedures, a normal (orderly) system shutdown should be
performed to prevent load equipment damage.
• Output Voltage THD - Indicates that the voltage distortion on one or more of the output phases
has exceeded the preset limit (normally 10% THD). The cause of the high output voltage distor-
tion should be investigated and corrective action (if any) taken.
••Transformer Overtemp - Indicates a unit transformer overtemperature condition. The cause
of the overtemperature condition should be investigated and corrected. Possible causes include
unit overload, excessive non-linear loading, inadequate ventilation, high or low input voltage, or
monitoring malfunction. Failure to correct the overtemperature condition may result in an auto-
matic system shutdown due to the second stage of overtemperature sensing.
• Output Overcurrent - Indicates one or more of the output phase currents has exceeded the pre-
set limit (normally 95% of the unit’s full load amp rating). The overcurrent condition should be
verified and corrective action taken. In the absence of other procedures, some of the output loads
should be turned off to reduce unit loading. If unbalanced phase currents exist, some of the loads
should be shifted from the higher loaded phase(s) to the lower loaded phase(s).
• Neutral Overcurrent - Indicates that the neutral current has exceeded the preset limit (nor-
mally 95% of the unit’s full load amp rating). The overcurrent condition should be verified and
investigated to see if corrective action is required. In some cases, high neutral current indicates
phase current unbalance which should be corrected. Where high neutral currents are the result of
harmonic load currents, all affected components (including output wiring) should be verified to be
suitable for the current.
• Frequency Deviation - Indicates that the output frequency has exceeded preset limits (nor-
mally Ø0.5 Hz). The frequency deviation should be verified and the cause investigated and cor-
rected.
• Phase Sequence Error - Indicates that the output phase sequence is not A, B, C. The phase
sequence should be verified and corrective action taken. Three-phase loads sensitive to phase
sequence should not be operated without proper phase sequence.
• Phase Loss - Indicates that one or more of the phase voltages is low or missing. The low voltage
condition should be verified and corrective action taken. In the absence of other procedures, a nor-
mal (orderly) shutdown should be performed to prevent equipment damage.
• Ground Overcurrent - Indicates the system ground current has exceeded the preset limit (nor-
mally 5 amps). The overcurrent condition should be verified and corrective action taken. Possible
causes are wiring errors, ground faults, or excessive leakage current.
• Customer Alarms (5) - Indicates customer-designated alarms. The cause and corrective action
depend on the nature of the alarm. See 1.3.6 - Control Wiring Connections for contact closure
connection information.