Tait T809-10, Руководство по обслуживанию

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34 Functional Testing
MBZ-00001-01
November 2004 Copyright © 2004 Tait Electronics Ltd
3 Set the output DC load to draw approximately 30A.
4
Switch on the mains supply and slowly decrease the load resistance, thereby
increasing the current until voltage foldback occurs. The current should not
rise above the Current Overload Limit (refer to Section 1.2.4), but voltage
should drop away and the ON LED’s intensity should decrease.
4.3 Output Noise
To check that output noise is within specification:
1 Ensure that the mains supply to the T809-10 is switched off.
2 Set up the test equipment as shown in Figure 4.1 .
3 Connect the T809-10 to the mains supply and switch it ON. The power
switch and the ON LED should be illuminated.
4
Connect a digital voltmeter (for example, Fluke 77) across the load terminals
and set the meter to its lowest AC volts range.
5 Check that the reading is less than 70mV
rms
AC under all load and line con-
ditions.
Note:
While the procedure outlined above will give a good indication of the out-
put noise level, an
accurate
reading is very difficult to obtain on a switched
mode power supply. This is because low noise levels, common mode noise
paths and ground loops all lead to inaccurate measurement results.
4.4 Overall Power Supply Stability
To check for overall PSU stability:
1 Ensure that the mains supply to the T809-10 is switched OFF.
2 Set up the test equipment as shown in Figure 4.1 .
3 Connect the T809-10 to the mains supply and switch it ON. The power
switch and ON LED should be illuminated.
4
Connect the oscilloscope across the output.
5 Vary the mains voltage and DC load over the full specified range (refer to
Section 1.2).
6 Check on the oscilloscope that no oscillations occur.