7300A User Manual
4-3
Control / Limits
4.2. LIMITATIONS ADJUSTEMENT (options)
The thyristor units are factory-calibrated to their nominal value: I
N
and P
N
= V
N
.
I
N
The limits can be adjusted by adjusting the values with the ‘I lim’ (multi-turn) and ‘VI lim’
(3/4 turn) potentiometers on the front panel.
4.2.1. CURRENT LIMITATION (options without
V
.
I control
)
The ‘I lim’ potentiometer enables to limit the load current to a chosen value.
The active state of the current limitation is indicated by a green flashing LED ‘Ilim’
The new current value I
max
can be recalibrated between 20% and 100% of I
N
.
Current setting
1. Turn the ‘I lim’ potentiometer fully round in the opposite direction to the arrow
(I
max
= 20% of I
N
).
2. Set the thyristor unit firing with 100% setpoint.
3. Measure the current value and use the ‘I lim’ potentiometer to set the desired value of
I
max
(new thyristor unit rating).
Current setting with
ICO
option
In ‘Burst mode’ with the ICO option the ‘I lim’ potentiometer is used to set the over-load
alarm (see page 5-8).
Over-load detection is signalled by flashing the red ‘
...
ICO’ LED.
To adjust the setting:
1. Turn the ‘I lim’ potentiometer fully round in the direction of the arrow (I
max
= 100% of I
N
).
2. Set the thyristor unit firing with 100% setpoint.
3. Rotate the ‘I lim’ potentiometer (one turn at a time at 5 second intervals) in the opposite
direction to the arrow until the ‘
...
ICO’ indicator starts flashing.
4. Rotate the potentiometer in the direction of the arrow by approx. 2 turns and
acknowledge the alarm (settings-calibration for the nominal load current used).
Important: If spurious alarms occur rotate the ‘I lim’ potentiometer in the direction of
the arrow, one turn at a time, until the alarms cease.
A
...
I
LIM
+
I
LIM
Current
calibration
potentiometer
Flashing:
current limit active
Green LED
