Siemens LMV3 series, Технические инструкции

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Technical Instructions LMV Series
Document No. LV3-1000
Section 5
Page 26 SCC Inc.
When set to Options 1 or 2 (activated or activated with analog input test), the VSD speed will be
shifted from the base VSD curve using the 4-20mA analog signal. This shift will occur when the
LMV3 reaches phase 60, and the shift delay (parameter 550/570) has timed out. The shift will
remain in effect until the end of phase 62 when the fuel valves close. Note that if the 4-20mA
analog signal stays at 10mA, no shift will be observed.
When set to Options 3 or 4 (activated with ignition speed shift or activated with analog input test
and ignition speed shift), the VSD speed will be shifted from the base VSD curve using the 4-20mA
analog signal. With these options, the shift has two parts. The first part is the ignition speed shift,
which is determined by the 4-20mA signal applied to the LMV3 during the end of phase 30
(prepurge). Once the LMV3 leaves phase 30, this amount of speed shift will be locked in for ignition
positon (P0). This amount of speed shift will continue until the LMV3 reaches phase 60, and the
shift delay (parameter 550/570) has timed out. After this timeout, the LMV3 will respond to the
current 4-20mA analog signal and shift the VSD speed accordingly.
Just like the previous modes, the shift will remain in effect until the end of phase 62 when the fuel
valves close. Note that if the 4-20mA analog signal stays at 10mA, no shift will be observed.
Options 2 and 4 add an analog input test to the functionality stated above. The analog input test is
an added requirement that must be satisfied on each start up so that the correct functionality of the
PLC or other device can be verified by the LMV3. The analog input test consists of the PLC or other
device sending a 10mA signal to the LMV3 in standby (phase 12) and a 4mA signal during traveling
to pre-purge (phase 24) for the first 2 seconds of pre-purge (phase 30). This would be accomplished
by the PLC or other device reading the LMV3 phase over Modbus, and then generating the
appropriate analog signal to match the phase.
8. After the VSD speed shift is activated, it is highly recommended to test the VSD shift settings,
especially if the settings are unproven for the application. This can be done by varying the 4-20mA
analog signal to the LMV3, and carefully approaching the VSD Shift High and VSD Shift Low limits.
This test should be done at each point (P1 – low fire, P2, P3, P4, up to P9 – high fire) to ensure that
the VSD Shift High and VSD Shift Low limits are safe for the application and that an unsafe fuel-to-air
ratio will not occur at these shift limits. It is also very likely that the VSD shift attenuation
(parameter 549/569) will need to be adjusted, since most applications require less VSD shift at low
fire to achieve a certain fuel-to-air ratio.
9. If ignition speed shift is utilized (Options 3 or 4), this should also be tested at VSD Shift High and VSD
Shift Low limits to ensure safe fuel-to-air ratios at light-off.
NOTE: It is the responsibility of the technician commissioning the VSD speed shift to ensure safe fuel-
to-air ratios at all points (P0 to P9) for the settings of VSD Shift High (parameter 548/568), VSD Shift
Low (parameter 547/567) and VSD Shift Attenuation (parameter 549/569). If settings of these
parameters are unproven for the application, tests at the VSD shift limits at each point (P0 to P9) must
be done.