AMETEK ASD Series - Manual (Page 63)

Sorensen ASD Series Programming: Digital Interface Control
M551177-01 Rev A 4-5
4.3 ADVANCED DIGITAL CONTROL FEATURES
4.3.1 SETPOINTS
ASD power supplies series have 3 modes of operation: voltage, current
and power mode. There are 3 analog inputs called programming inputs
that define the setpoints when analog programming mode is used. There
are 3 registers that define the setpoints when digital programming is used
(see DIGITAL PROGRAMMING MODE bit in the command register).
In analog programming mode, the setpoint registers are automatically
updated with the values of the analog inputs. Writing to them has no
effect.
If a value beyond the limits is written to the setpoint registers, the actual
written value is saturated to the maximum limit. For example, is a 100V
setpoint is written to a 60V unit, the actual written value will be 60V.
4.3.2 REMOTE VOLTAGE SENSING
ASD units have both local and remote voltage sensing capabilities.
Remote sensing allows closing the voltage loop right at the load terminals,
compensating for load cable voltage drops. The maximum remote sensing
compensation is 50% of full scale voltage, giving up to 2% extra voltage
(on top of the nominal voltage rating) in case it is needed. Having local
and remote sensing allows also monitoring load cable voltage drop and
impedance, in order to detect load cable or connection issues.
Maximum accuracy of the voltage measurement is obtained by using
remote sensing.
4.3.3 LOAD IMPEDANCE MONITOR
The load impedance monitor feature performs a calculation in real time of
the load impedance, based on the output voltage and current
measurements. If the output impedance monitor is enabled (“IMPEDANCE
MONITOR” bit in the command register), the load impedance calculation is
continuously compared to programmable maximum and minimum values.
If
the output impedance falls outside this window, a
“FAULT_OUTPUT_IMPEDANCE” fault will be generated, which can shut
down the unit if desired (see Programmable Fault Behavior).
ASD units also monitor how the load impedance changes with time, which
is called impedance “rate-of-change” (ROC). This is intended to show
sudden changes in impedance caused by failures, as opposed to the
typically slow changes in impedance caused by temperature changes of
the load. There is also a maximum limit and a minimum limit for this
variable, specified in percent of change per second. If the rate of change is
outside this window, the master controller will generate a fault.