Current Limit; Transient Recovery Time; Transient Recovery Time, Test Setup - HP BENCH Series Operating And Service Manual

h. Using formula of step f, calculate output
impedance at frequencies of 50 kHz and 500kHz.
Values should be less than 0. 5 ohm and 3. 0 ohms,
respectively.
5-37 Output Inductance. To check the output in
ductance, repeat steps a through f at frequencies
of 10 kHz, 50 kHz and 100 kHz. Calculate the out
put inductance (L) using the following formula:
L = — (gee Note)
2 w f
The oscillator frequency is equivalent to f in the
equation. The output inductance should be less
than 20 microhenries.
NOTE
The equation assumes that Xl is much
greater than Rout and therefore XL = Zout.
5-38 CURRENT LIMIT
5-39 To check the current limiting characteristics
of the supply, proceed as follows:
a. Attach the multimeter or a milliameter to
the output terminals of the supply. Set the meter
for approximately 600 mA. The internal resistance
of the meter is low enough to overload the supply
so that the output will current limit.
b. Adjust the VCLTAGE controls fully
clockwise.
c. The meter should read as follows:
Model 62I3A I300 ±50mA
6215A 475 ± 10mA
6217A 250 ± 10mA
5-40 TRANSIENT RECCVERY TIME
Definition: The time "X" for output
voltage recovery to within "Y"
millivolts of the nominal output
voltage following a "Z" amp step
change in load current — where:
"Y" is specified separately for
each model but is generally of the
same order as the load regulation
specification. The nominal output
voltage is defined as the DC level
half way between the static output
voltage before and after the imposed
load change, and
"Z" is the specified load current
change, normally equal to the full
load current rating of the supply.
5-41 Transient recovery time may be measured at
any input line voltage combined with any output
voltage and load current within rating.
5-42 Reasonable care must be taken in switching
the load resistance on and off. A hand-operated
switch in series with the load is not adequate,
since the resulting one-shot displays are difficult
to observe on most oscilloscopes, and the arc
energy occurring during switching action complete
ly masks the display with a noise burst. Transis
tor load switching devices are expensive if reason
ably rapid load current changes are to be achieved.
5-43 A mercury-wetted relay, as connected in the
load switching circuit of Figure 5-9 should be
used for loading and unloading the supply. When
this load switch is connected to a 60 Hz AC input,
the mercury-wetted relay will open and close 60
times per second. Adjustment of the 25K control
permits adjustment of the duty cycle of the load
current switching and reduction in jitter of the os
cilloscope display.
5-44 The maximum load ratings listed in Figure 5-9
must be observed in order to preserve the mercury-
wetted relay contacts. Switching of larger load cur
rents can be accomplished with mercury pool relays;
with this technique fast rise times can still be ob
tained, but the large inertia of mercury pool relays
limits the maximum repetition rate of load switching
and makes the clear display of the transient recovery
characteristic on an oscilloscope more difficult.
POWER SUPPLY
UNDER TEST
OSCILLOSCOPE
hp I40A
■oVp
CONTACT PROTECTION
NETWORK
Rl
• luF 5n,5W
400V (NOTE 3)
1{ —WSr
II5V I I
60CPS I 2W 3W 7 ,
4Y-r|-izr^
i>-| I LI N E S^H '^^2
O
I REPETITIVE
[l^AD__S\^TC^ {I^TJ_I) I
NOTES:
1. THIS DRAWING SHOWS A
SUGGESTED METHOD OF
BUILDING A LOAD SWITCH,
HOWEVER OTHER METHODS
COULD BE used: SUCH AS
A TRANSISTOR SWITCHING
NETWORK. MAXIMUM LOAD
RATINGS OF LOAD SWITCH
ARE: SAMPS, 500 V, 250 W
(NOT 2500W )
2. USE MERCURY RELAY;
CLARE TYPE HGP 1002 OR
W. E. TYPE 276B.
3. USE WIRE WOUND RESISTOR.
MODEL NO.
"l
62I3A/62I4A
62I5A/62I6A
62I7A/62I8A
ion, IOW,i5%
65n, low,±5%
250n, IOW.i5%
Figure 5-9. Transient Recovery Time, Test Setup
5-7