DER2 digital regulator instruction manual - rev. 02 - pag. 29
6.2 V/F slope at start up
Parameter P[24]
sets the slope proper voltage / frequency at start up. After the underspeed alarm frequency
threshold has been exceeded (set by parameter P[21] or by the Hz trimmer), the work ramp is used
(parameter P[23]).
The default value is 1250; an increase in the value of P[24] will cause a greater reduction of low frequency
voltage; a decrease in the value of P[24] will cause a lower reduction in voltage, up to the limit of P[24]=0,
which means that no reduction in voltage will take place.
WARNING:
If the voltage is not lowered enough with low frequency and the alternator is operating
in these points, overheating could develop that is dangerous for the machine.
6.3 Short circuit time
Parameter P[25]
defines the operating time with the alternator short circuited, which is expressed in tenths of
a second (from 0.1 seconds to 25.5 seconds); after this period of time the regulator goes to the blocked
status; a value of 0 disables the blockage.
6.4 Intervention threshold of low excitation alarm
If the measured value of excitation voltage does not fall within a preset value range, the low excitation or the
excitation lost condition is signaled (visible on the main panel of the DxR Terminal through the A-08 alarm in-
dicator); no other action is performed by the regulator, except for the switching of APO (if set).
The numeric value identifying in real time the excitation condition is available at location L[56]; the upper de-
tection threshold cannot be modified while the lower threshold can be configured through parameter
P[27].
The alarm is activated when the value assumed by location L[56] is higher than the upper threshold or lower
than the value assumed by parameter P[27]
For the generators in stand-alone operations, the loss of excitation, on a working regulator, implies also the
activation of the low voltage alarm. The underexcitation / loss of excitation alarm is mainly intended for the
applications in grid-parallel mode, provided that the regulator stay fully operational (for instance with sufficient
residual voltage, direct supply from the phase or from PMG).
WARNING:
In case of parallel operation of the generators and, most of all, in case of grid-parallel
mode, given that the activation of the
underexcitation/loss of excitation alarm does not imply any other action, except for the signalling
and switching of APO (if enabled), the protection of the system is transferred to at least an appro-
priate management of the above-mentioned signalling. However, no guarantee is offered for the
capacity of the exclusive use of this protection to safeguard the system from all the possible func-
tional anomalies correlated to underexcitation / loss of excitation.
5. Overspeed
Parameter P[26]
sets the overspeed alarm intervention threshold; if it is set on 0, the signal cuts in at 55 Hz
(if the 50/60 jumper and 50/60 setting in the
Settings/UFLO&LAMS
Menu are absent) or at 66Hz (if the
50/60 jumper is present and enabled or the 50/60 flag in the
Settings/UFLO&LAMS
Menu is activated).
Values between 65535 (-1) and 32768 (-32767) lower the threshold proportionately to 50 Hz and 60 Hz,
respectively; values between 0 and 32767 raise the threshold proportionately, respectively to 60 Hz and 72
Hz; refer to the broken lines in figure
10a.
6. Other parameters
6.1 Vout / Vaux Ratio
In order to guarantee sufficient feeding voltage at speeds lower than the Hz protection intervention threshold,
a limit to the reduction of voltage has been foreseen, as a function of frequency.
The limit concerns regulated voltage (Vout). Should the DER2 be powered through an auxiliary winding, it
must be born in mind that the voltage generated by the winding (Vaux) may not have the same Vout value;
Vaux is considered proportionate to Vout and the proportional coefficient is determined by
parameter P[14].
If the DER2 is powered directly by the regulated phase, parameter 14 should be set on 0; in case it is
powered by auxiliary winding or PMG, the voltage (Vaux) must be measured, in no-load conditions and with
output voltage regulated on the nominal value (Vout); the value of parameter P[14] can be obtained with the
following formula:
1
32767
]
14
[
Vaux
Vout
P
