TTI QPX600D Instruction Manual page 18

It should be noted that the unit can only source current and cannot sink it, thus units cannot be
series connected in anti-phase.
The unit can be connected in parallel with others to produce higher currents. Where several units
are connected in parallel, the output voltage will be equal to that of the unit with the highest output
voltage setting until the current drawn exceeds its current limit setting, upon which the output will
fall to that of the next highest setting, and so on. In constant current mode, units can be connected
in parallel to provide a current equal to the sum of the current limit settings.
Note that the output terminals are rated at 60A maximum; if several outputs are operated in
parallel to source higher currents than this the junction should be made at a separate point, not
one of the terminals.
Over-Voltage Protection
Over-Voltage Protection (OVP) can be set from 2.0V to 90.0V. If the output voltage exceeds the
set OVP the output is immediately turned off (typically within 100µs), thus avoiding damage to the
circuit under test. The OVP circuit will trip if an excessive voltage is accidentally set from the front
panel or via a remote control interface, or is the result of a failure in the control circuitry of the
instrument itself. OVP will also trip if an excessive voltage is impressed across the terminals from
an external source; however, when the output is tripped off, the external voltage will still be present
and it is up to the user to remove the source to avoid possible damage.
To set OVP press SHIFT, OVP. The display changes to show only the present
with the prompt
value using the numeric keypad, exactly as described for setting output voltage, and press OK to
confirm the new setting; to exit without entering a new value press ESCAPE. The factory default
setting is 90·0V.
If the OVP is tripped the display shows the message
the output is turned off. Pressing ESCAPE at this point removes the message and the display now
shows the preset voltage and current limit. When the cause of the OVP has been removed (or the
OVP limit changed) the output can be turned on again.
Note also that it is possible and valid to set OVP below the set voltage. If the supply is in constant
current mode the output voltage will be below the set voltage; OVP could be set such that is was
above the actual output voltage but below the set voltage. This could be used to trip the output
under a fault condition which caused the load impedance to increase and the actual output voltage
to therefore rise above the OVP point.
Over-Current Protection
Over-Current Protection (OCP) can be set from 2.0A to 55.0A. If the output current exceeds the
set OCP the output is shut down (typically within 100ms).
To set OCP press SHIFT, OCP. The display changes to show only the present
together with the prompt
new OCP value using the numeric keypad, exactly as described for setting the current limit, and
press OK to confirm the new setting; to exit without entering a new value press ESCAPE. The
factory default setting is 55·0A.
If the OCP is tripped the display shows the message
output is turned off. Pressing ESCAPE at this point removes the message and the display now
shows the preset voltage and current limit. When the cause of the OCP has been removed (or the
OCP limit changed) the output can be turned on again.
Note also that it is possible and valid to set OCP below the set current limit. For example, the
power supply may be used to repetitively test a unit under test (UUT) which normally takes a peak
current of, say, 10 Amps. However, a faulty UUT would take a current of more than 10 Amps and
would be damaged by being left in a 10 Amp current-limited state. In this case the current limit
could be set to 11A, say, and the OCP set to 10A to ensure that a faulty UUT will trip the supply off.
Numeric Entry: Range 2-90
Numeric Entry: Range 2-55
; the OK lamp flashes. Enter the new OVP
OVP - Press ESC to Reset
; the OK lamp flashes. Enter the
OCP - Press ESC to Reset
OVP setting together
and
setting
OCP
and the
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