Chapter 14 - Monitoring and Control
SYSTEM CHECK PSL
Check Sync 1 OK
Check Sync 2 OK
Figure 170: System Check PSL
Slip control can be achieved by timer, by frequency or by both. The settings CS1 Slip Control and CS2 Slip Control
are used to determine which type of slip control is to be used. As the device supports direct measurement of
frequency, you would normally use frequency.
If you are using Slip Control by Timer, the combination of Phase Angle and Timer settings determines an effective
maximum slip frequency, calculated as:
2A/360T – for CS1
A/360T – for CS2
A = Phase Angle setting in degrees
T = Slip Timer setting in seconds
For CS1, where the Phase Angle setting is 30° and the Timer setting is 3.3 s, the "slipping" vector has to remain
within +/- 30° of the reference vector for at least 3.3 seconds. Therefore a synchronisation check output will not be
given if the slip is greater than 2 x 30° in 3.3 seconds.
Therefore, the maximum slip frequency = 2x30/360x3.3 = 0.0505 hz.
For CS2, where the Phase Angle setting is 10° and the Timer setting is 0.1 sec., the slipping vector has to remain
within 10° of the reference vector, with the angle decreasing, for 0.1 sec. When the angle passes through zero and
starts to increase, the synchronisation check output is blocked. Therefore an output will not be given if the slip is
greater than 10° in 0.1 second.
Therefore, the maximum slip frequency = 10/360x0.1 = 0.278 Hz.
Slip control by Timer is not practical for "large slip/small phase angle" applications, because the timer settings
required are very small, sometimes less than 0.1 seconds. For these situations, slip control by frequency is better.
If Slip Control by Frequency + Timer is selected, for an output to be given, the slip frequency must be less than
BOTH the set Slip Freq. value and the value determined by the Phase Angle and Timer settings.
Man Check Synch
AR Sys Checks