Section 4: Using the Model 9100: AC Harmonics Function 4.21-7
Final Width = 215mm
4.21.3.4 Conditions for Operation
Same Frequency
For any two 9100 units (Master and Slave), both must be set to the same frequency of
1kHz or lower, before the output of the Driven unit is turned on.
Good Practice
In general, a slave unit will be well-behaved if the synchronizing pulse is interrupted.
However, as the voltage increases above a few hundred volts, and the frequency decreases
below 100Hz, synch. pulse interruptions or shifts may cause transients which result in
operation of the protection circuitry in the slave unit, automatically turning the slave unit
output OFF.
Only select phase locking while inputs are driven or, at least,
terminated.
If units are run as slaves at HV AC and LF observe the precautions described in the
following paragraph.
Change of Function - Reference 9100 Unit
If the Reference unit’s function is changed from ACV, its reference output will go low.
This will cause the Driven unit to unlock and free-run, being most unlikely to remain in
phase with the Reference unit. External control will be re-established when the Reference
unit is returned to ACV function (or placed in ACI function). At this time the Driven unit’s
phase will be switched rapidly, creating transient disturbances in the output AC Power
unless it is switched off. The Driven unit’s output must therefore be tumed OFF before
the reference unit is returned to any AC function, (Power, ACV or ACI).
Disconnection of the cable from the Reference input (‘PHASE LOCK IN’ on the rear
panel) will also cause the Driven unit to free-run, with resultant phase-shift of its output
and possible transients when reconnected. Again, the Driven unit’s output must be turned
OFF before the cable is reconnected.
It is also poor practice to demand large frequency shifts when high currents are selected
on the slave or even the internal auxiliary channel. This creates an inductive spike due
to the output wiring or load, which can trip the over-compliance detector. If this happens,
simply turn the output back ON. Procedure writers should consider turning the output
OFF before any significant change to avoid any possibility of nuisance tripping.
Lead Set
The 9104 lead has been optimised for this application. Use of untwisted replacements
may result in increased voltage errors when high currents are selected. The 9100
specification assumes the use of the 9104.
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