Setting The Current Limit; Activating The Channels - Hameg HMP Series User Manual

4 .5

Setting the Current Limit

A current limit indicates that only a specific maximum
current I can flow. Prior to operating an experimental
max
circuit, this maximum value will be selected at the power
supply. The intent is to prevent damage to the experimen-
tal circuit in case an error occurs (e.g. a short circuit).
U
out
U
max
Voltage regulation
Fig. 4.5: Current limit
As the diagram shows, it remains true that Uout = Umax
will remain stable as long as the output current Iout < Imax
(voltage regulation). If the selected current value Imax is
exceeded, the current control (Constant Current operating
mode) is applied. This means that despite an increased
load, the value Imax can no longer increase. Instead, the
voltage Uout will decrease below the nominal value of
Umax. However, the current flow remains limited to Imax.
If the OUTPUT key and VOLTAGE key are activated and the
selected channel is changed, the blue LED of the respec-
tive channel will flash alternately in green (CV = Constant
Voltage) and red (CC = Constant Current), depending on
the operating mode.
After switching on the power (OUTPUT Off) the instrument
will always be in the constant voltage operating mode. The
maximum current Imax corresponds to the setting on the
CURRENT key. Once the CURRENT key has been activated,
the corresponding channel can be selected. The value is
selected via knob or arrow keys. The current is selected
individually for each channel. Once the setting has been
completed, press the CURRENT key again. Otherwise, the
instrument will automatically switch back after 5 seconds,
without the changes taking effect (see chapter 5.3.7 Key
Fallback Time).
I
10
(5)
5
(2,5)
(0) 0
0
Fig. 4.6: (HMP2030) HMP2020/4030/4040 power hyperbola
The combination of selected voltage and selected current
limit results in the following power hyperbola:
According to the electrical basic formula for power P = U,
the following results for the maximum power per channel:
Current control
I
I
out
max
16 32
CH1 = 160 W, CH2 = 80 W (188 W max.)
HMP2020:
80 W per channel (188 W max.)
HMP2030:
HMP4030: 160 W per channel (384 W max.)
160 W per channel (384 W max.)
HMP4040:
For instance, for the HMP2020 at 160 W per channel for
a 24 V voltage, this would result in a maximum current of
6.67 A, and .3.33 A for the HMP2030.
To protect a connected, sensitive load even better, the
HMP series includes an electronic fuse. The FUSE key
allows the selection or deletion of fuses. For the fuse
selection the FUSE button will be activated (FUSE-LED will
be illuminated) before choosing the appropriate channel. If
the respective channels are selected with FUSE, the
channel LEDs will be illuminated in blue. Press the FUSE
key again to complete the setting for the electronic fuse.
Without any input, by default the instrument will switch
back after 5 seconds (see chapter 5.3.7 Key Fallback Time).
After the instrument has been switched back, the channel
LEDs will be illuminated in green again. In the display,
FUSE will be shown for each channel (see fig. 4.7).
4 .5

Activating the Channels

For all HAMEG power supplies, the output voltages can
be switched on and off via key (OUTPUT). The power
supply itself remains switched on. This allows you to con-
veniently select the desired output parameters up front
and subsequently connect to the load via the OUTPUT key.
If the OUTPUT key is activated, the respective LED will be
illuminated in white.
As a result of the inline regulator concept, naturally a ca-
pacity is required at the output to achieve ambitious goals
regarding Noise/Ripple. It required high technical com-
plexity (for instance by means of internal current sink) to
reduce the screening capacity visible for the load to a mini-
mum. To prevent unintended transient currents, please be
sure to deactivate the respective output before activating a
V
load, then connect the load and as a last step activate the
output. This allows you to implement an optimal transient
response when activating the output. Be sure to operate
highly sensitive semiconductors, such as laser diodes, only
as specified by the manufacturer.
Operating the HMP Series
Fig. 4.7:
HMP2030 /
HMP4040 Fuse
appearance in
the display
33