Wayne Kerr AP10030, Руководство пользователя и обслуживания

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Wayne Kerr AP 1kW Power Supplies • Issue 2 29
To maintain the temperature coefficient and stability specifications of the supplies, the
external resistors should be low noise and low temperature coefficient (50ppm per
°
C)
types.
When choosing resistor values, a compromise has to be found between programming
speed (which is impaired when the source impedance of the voltage programming
sources is greater than a few k
Ω ) and resistor dissipation (which increases with lower
values). If R
Y
is kept below 5k
Ω
, this will have little effect on the programming speed.
d) Positive And Negative Tracking Supply
Positive and negative tracking outputs can be achieved by earthing the centre of the
power supply chain. Alternatively, it can be earthed at any point if an unbalanced
positive and negative supply is required. However, no power supply output must exceed
200V d.c. with respect to earth.
e) Overvoltage Trips
The overvoltage trip on the master unit can be used as an overall system trip. To do this
the master level is set to just above the output voltage that the master should be
delivering when the total load voltage is at the desired limit point. When the master trips,
the slave units will programme down to minimum output voltage. The trips on the slave
units can also be set if required. This gives maximum protection but leads to a greater
likelihood of false tripping.
f) Remote Sensing
Remote sensing of the load voltage is achieved as follows:
i) Disconnect the link joining terS and + on the master.
ii) Connect the +S terminal to the positive end of the load (positive sense lead).
iii) Disconnect the link joining -S and - on the most negative slave unit.
iv) Connect the -S terminal to the negative end of the load (negative sense lead).
See section 6.4.2. for further information on remote sensing.
g) Remote programming
The master power supply may be remotely controlled by any of the normal methods of
remote programming. These are described in section 6.4.3.
When remotely programming master-slave series combinations, care should be taken to
ensure that programming input voltages or resistors are referenced to the negative
terminal of the master unit. The master unit is always the most positive unit of the
combination. Therefore the reference terminal will be at a voltage between that of the
combination output terminals and not necessarily at earth potential.