CG Drives & Automation, 01-5980-01r2 Main features 59
Load monitor alarm actions
All the alarms and pre-alarms can be independently
configured to affect operation by applying an alarm action,
e.g. a trip or a warning. See section 7.3.1, page 55. The
alarm or pre-alarm status is available on the programmable
relays if so configured (see menu [550] for more
information).
The alarm actions for both the autoset alarm levels and the
manually set alarm levels are configured in menu [4111],
[4121], [4131] and [4141].
The corresponding “Alarm Delays”, which will affect the
alarm response time, are set in menu [4113], [4123], [4133]
and [4143].
Load monitor during start-up
To avoid faulty alarms due to initial over- or underload
situations at start, a “Start Delay” time can be applied for the
load monitor. See menu [416], page 101.
Example 1: Configuring alarm levels manually
Assume that the load monitor is intended to be blocked
during the start-up procedure. A start delay of 30 seconds is
therefore selected in menu [416], in order to allow the
process to settle before the load monitoring becomes active.
In this case a pump must be protected from both overload
and underload (e.g. cavitation) conditions, but no pre-
alarms are needed. The alarm action for the pre-alarms
([4121] and [4131]) is therefore set to “No action”.
Furthermore, the alarm actions for Max alarm [4111] and
Min alarm [4141] are set to “Soft Trip”, with the
corresponding alarm delays; 10 seconds in menu [4113]
Max Alarm Delay, and 5 seconds in [4143] Min Alarm
Delay.
Since the normal load condition (shaft power) for the pump
is 50% of the nominal motor power [223], the Max Alarm
Level [4112] is set to 70%. Finally the Min Alarm Level
[4142] is set to 10%, which is reached during e.g. pump
cavitation conditions.
This configuration results in the following sequence of
events (as illustrated in Fig. 42):
A. The load monitor function is activated when the set start
delay time (30 seconds) has expired.
B. A maximum level is exceeded, but since the load returns
to a safe level within the set alarm delay time (i.e. <10
seconds) no alarm action is performed.
C. The maximum alarm level is exceeded again.
D. When the set alarm delay time (10 seconds) has expired,
the maximum alarm action is executed (in this case a soft
trip, as set in menu [4111]).
Fig. 42 Example 1: Manually set load monitor function.
Example 2: Auto-setting alarm levels
To block the load monitor during the start-up, a start delay
of 30 seconds is selected in menu [416].
In this case a motor used in a conveyor application must be
protected. It is only of interest to apply a maximum alarm
and maximum pre-alarm, therefore the alarm actions for the
minimum alarm [4141] and the minimum pre-alarm [4131]
are set to “No action” (default). The Max Pre-Alarm Action
[4122] is set to “Warning” and the Max Alarm Action
[4111] is set to “Hard Trip”. Then the Max Alarm Delay
[4113] is set to 3 seconds, and the Max Pre-Alarm Delay
[4123] to 0 seconds to get an instant warning when the load
is increased. Menu [4171] Max Alarm Margin is set to 10%,
and menu [4172] Max Pre-Alarm Margin is set to 5%, to
indicate that an overload condition is close.
The motor is started and the actual shaft power is viewed to
the left in menu [4175] Autoset Alarm. When the process
has stabilised, this indicates that the normal load conditions
take place at 60% of the nominal motor power [223]. The
autoset of the alarm levels is done by selecting “Yes”,
followed by pressing “ENTER”. “Autoset OK!” is displayed.
The motor is now fully protected with a maximum alarm set
to 70% (Normal Load + Max Alarm Margin, 60% + 10%)
and a pre-alarm at 65% (Normal Load + Max Pre-Alarm
Margin, 60% + 5%). The “Normal Load” value is viewed in
menu [4176], along with the actual shaft power value.
The following events are noted (see Fig. 43):
A. The load monitor function is activated when the set start
delay time (30 seconds) has expired.
B. The maximum pre-alarm level is exceeded, and
immediately results in a warning message: ”Mon
MaxPreAl”, as there is no alarm delay in this case.
C. The maximum alarm level is exceeded.
D. When the set maximum alarm delay time (3 seconds)
has passed, the set maximum alarm action is executed, in
this case a Hard trip, as set in menu [4111].
NOTE: The load monitor alarms are disabled during
jogging, braking, and stop ramp.
30 s. 10 s.
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