DER2 digital regulator instruction manual - rev. 02 - pag. 31
2. Description of alarms
N.
Description of event
Action
1
EEPROM checksum
Verified upon start up (after DSP reset and initialisation of the peripheral). The
actions undertaken are: signalling, locating of default settings, saving in EPPROM
and regulator blockage.
When the machine is switched on again, if the EEPROM is damaged, the alarm
will be repeated. Otherwise the regulator will begin to function with default
parameters.
2
Over Voltage
The alarm does not determine a change in the LED flash, the APO output is active
and the alarm is memorised. This can be caused by abnormal operating conditions
(such as overspeed or overloading) or by a breakdown of the regulator. The over
voltage alarm is activated if the output voltage is lost. The over voltage is
calculated using an opportune template, as a function of the speed and is inhibited
during transition, for 2 seconds. In the template for the calculation the threshold is
set at 5% above the nominal value.
3
Under voltage (@
ω
N
)
The alarm does not determine a change in the LED flash, is stored and the APO
output is active. The under voltage is calculated using an opportune template as a
function of the speed (which can be seen in the description of the over voltage
alarm); in the template for the calculation the threshold is set at under 5% the
nominal value. It intervenes only above the underspeed alarm threshold; it is
practically inhibited by this. It is also inhibited in the ent of intervention of the
Excitation over voltage and during transients.
4
Short circuit
The alarm is disabled under 20 Hz, is visualised upon activation of the action and
memorised. Tolerated short circuit time goes from 0,1 to 25,5 seconds
(programmable in 100 ms steps); then the regulator is blocked after saving DD
and TT and signals the STOP status. With the time in short circuit set on zero, the
blockage is disabled. The STOP condition causes a fall in excitation, with
consequent switching off and successive restarting of the regulator and therefore
repetition of the cycle.
5
Excitation Overcurrent
The function of this alarm is not only to signal an excessive temperature, but it also
has an active function in reducing the cause. In fact, there is an adjustment ring
that takes control of voltage after the threshold has been exceeded; the action
involves reduction of the excitation current and therefore output voltage.The
available parameter is the "current threshold", which determines the balanced
value at which the system is stabilised. The alarm is signalled and stored. For
calibration see the paragraph on excitation overcurrent.
6
Underspeed
Signalling (immediate) and activation of the V/F ramp. This alarm also appears
when the machine is started and stopped. The alarm is not saved among
EEPROM data. The alarm intervention threshold depends upon the status of the
50/60 jumper (hardware or software) and on the position of the Hz trimmer or the
value of parameter P[21]. Under the threshold the V/F ramp is active.
7
Overspeed
This is visualised in the same manner as the underspeed alarm and does not
involve actions on control, but the alarm is stored. The overspeed condition may
provoke an over voltage as in the case of capacitive load. The threshold can be
set with parameter P[26].
TABELLA 14 : DESCRIPTION OF ALARMS
8
underexcitation /loss of
excitation
The alarm does not determine a change in the LED flash, enables APO output and
is memorized. The alarm condition is recognized by a underexcitation / loss of
excitation observer, available for reading at location L[56]: if the value of L[56] is
higher than the upper (fixed) threshold or lower than the value of the lower
threshold (parameter P[27]), A-08 is activated. The alarm is inhibited during
transients.
NOTE
: Though the voltage is continuously regulated, the DER2 will switch off if the frequency goes
under 20Hz. To reset the system it is necessary to stop completely the alternator.
