Over-Current Protection; Output Protection; Output Power (V X A); Temperature Trip - TTI QL Serie Manual De Instrucciones

Over-Current Protection

Over-Current Protection (OCP) can be set from 0·01A to 5·5A (QL355), 0·01A to 4·4A (QL564). If
the output current exceeds the set OCP the output is shut down (typically within 35ms).
To set OCP press SHIFT, OCP; the 10mA step JOG indicator will start flashing and the jog rotary
control can be used to increment/decrement the OCP setting in 10mA steps. Press OK to confirm
the new setting; to exit without entering a new value press ESCAPE. The factory default setting is
5·50A.
If the OCP is tripped the display shows the message
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 that as with OVP, the OCP setting is not changed when the range is changed.
Note also that 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, 2 Amps. However, a faulty UUT would take a current of more than 2 Amps and would be
damaged by being left in a 2 Amp current-limited state. In this case the current limit could be set to
2·1A, say, and the OCP set to 2·0A to ensure that a faulty UUT will trip the supply off.

Output Protection

In addition to OVP and OCP for forward over-voltage and over-current protection, the output is
protected from reverse voltages by a diode; the continuous reverse current must not exceed 3 Amps
although transients can be much higher.

Output Power (V x A)

If SHIFT, V x A is pressed the voltage display shows the product of measured output voltage x
measured current and the current display shows
instantaneous, not a continuous, reading of the output power; the reading is held whilst the key is
pressed. Pressing V x A cancels SHIFT. Jog is temporarily disabled (and the JOG indicators are
turned off) during the V x A display.

Temperature Trip

If the safe internal temperature limit is exceeded because, for example, the fan vents have been
blocked, the output is turned off and the display will show
point will do one of two things:
i. If the over-temperature condition has already cleared the message will be removed and the
display will show preset voltage and current limit. Assuming the cause of the over-temperature
has been rectified the output can be turned on again.
ii. If the instrument is still above the safe temperature limit the
slowly ('lazy' flash) until the instrument has cooled, at which point the display will show preset
voltage and current limit again. Assuming the cause of the over-temperature has been
rectified the output can be turned on again.

Alarm Output

The recessed 2-pin connector on the rear panel is directly connected to an opto-coupled NPN
switching transistor (pin 1 emitter, pin 2 collector) which is turned on (i.e. switch 'closure') according
to the conditions specified in the Extra Functions section, see later. The default condition is switch
closure for any trip condition (OVP, OCP, SENSE or OTP). The maximum open-circuit voltage
permitted across the switch is 30VDC and the nominal sink current for switch closure is 1mA.
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and the output is turned off.
OCP triP
. V x A is a momentary function, i.e. it gives an
UA
OTP triP . Pressing ESCAPE at this
OTP triP
message will flash