ABB RELION REX640 - Page 1576

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
tpf
s
s
df
dt
=
± −
± max
2
(Equation 363)
s Measured frequency difference across the CB to be synchronized
+smax Setting Freq Diff Ov Synch
-smax Setting Freq Diff sub Synch
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.
Control functions
1MRS759142 F
1576 REX640
Technical Manual