MarelliMotori MEC-100 Manuel De L'utilisateur page 70

Should the generator voltage increase in the presence of an inductive load, you need to check that:
•
the U phase is connected to S1 and the V phase is connected to S2.
•
current is measured on phase W.
If both conditions are met, you will need to invert the two leads from the measuring TA on the generator current
measurement terminals.
Droop can be set from 0 to 10%, with increase of 0.1%, with phase current equal to the rated generator current and power factor
corresponding to 0.80. This function is enabled by closing the PAR contact (C5 contact, see Par. 3.5.5). It can only be activated
in AVR Mode. The switching to the PF or VAR Mode disables automatically the Reactive Droop Compensation. During parallel
operation between two or more generators (PAR contact closed), the LED corresponding to the Reactive Droop Compensation
item in the system status window in System Monitoring becomes green.
3.10. SOFT-START
The MEC-100 provides the SOFT-START function to bring linearly the generator voltage from the residual value to the
reference one, in a time interval whose length can be defined, with minimum overshoot. For this function, it is enough to set only
one parameter: that is, the ramp-up time of the voltage setpoint. This parameter, whose value is included between 0 and 3600s
with increases of 1s, accounts for the time necessary to the MEC-100 to lead the voltage setpoint from 0Vac to 100% of its
predefined value (the rated voltage), starting from the moment when the MEC-100 is enabled from the START contact. In Fig.
3.10.a. the ideal time diagram of the voltage setpoint during the SOFT-START function is shown.
The diagram in Figure 3.10.a refers to the ideal curve which the card processor makes the voltage setpoint follow to
reach 100% of the pre-established value. Obviously, under real conditions, and especially at full rpm, the generator
voltage does not start from 0Vac, but from the residual machine voltage value; moreover, under real conditions,
starting from 0rpm up to reach the rated speed, the voltage ramp-up may not be perfectly linear, but on the contrary
may present a light overshoot at low frequencies and voltages (in any case included within a range of not significant
values).
3.11. SETTING THE P.I.D. PARAMETERS
One of the functions which make the MEC-100 a particularly efficient and flexible device is the configurability of the parameters
that define the transient performances and the stability of the control system.
In particular, the MEC-100 system allows to use P.I.D. (Proportional, Integral, Derivative) controllers which can be individually
set by the direct insertion of the values corresponding to the relevant constants: K
3.11.1. Proportional, Integral and Derivative Controllers
In the Table below an indicative scheme is provided where the K
hypothesis of submitting the closed chain system to a step input.
963857137_M
V
[%]
100%
START
Generator Voltage Setpoint when the SOFT-START Function is Active
Ramp Time
Fig. 3.10.a
, K
P
, K , and K
P I D
MEC-100 – Marelli Motori
t
, and K .
I D
values are determined starting from the
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