ABB RELION REX640 Technical Manual page 1425

1MRS759142 C
REX640
Technical Manual
If the frequency difference (DF) is positive, it means the reference side frequency is
lower than the running side frequency. So the frequency matching generates
frequency lower command pulse LOWER_F.
The length of the frequency raise and lower command pulses (tpf) and pulse off
interval (tsf) are calculated based on the setting Frequency match mode.
Frequency matching in manual mode
If Auto Syn mode is set to "Manual mode", the frequency raise or lower command
pulses are generated manually from the function's user commands.
If the command Gov frequency raise is set to "RAISE", the function activates the
frequency raise command pulse RAISE_F. If the command Gov frequency lower is
set to "LOWER", the function activates the frequency lower command pulse
LOWER_F.
The length of these generated pulses tpf and pulse off interval tsf are based on the
settings as: tpf = Freq pulse Min Dur; tsf = Freq pulse off Intv.
Frequency matching with variable command pulse lengths
When the setting Frequency match mode is set to "Variable Pulse", the frequency
matching is done with variable command pulse lengths.
The frequency matcher issues a command with a length proportional to the current
slip. The proportionality factor df/dt can be adapted to the governor. The frequency
matcher aims at a value midway between the nearer slip limit and zero.
The adjusting frequency command pulse length tpf is calculated as
s
± max
s
± −
2
tpf
=
df
dt
GUID-FACB720C-38B5-4F83-AB69-4A00569C9F76 V1 EN
s Measured frequency difference across the CB to be synchronized
+smax Setting Freq Diff Ov Synch
Freq Diff sub Synch
-smax Setting
df/dt Setting Freq rate of change
The command length does not fall below a settable minimum value Freq pulse Min
Dur. After an adjusting command, the system waits for the set Freq pulse off Intv (tsf)
so that the actual values can stabilize to the new set point.
Section 9
Control functions
(Equation 328)
1419