Dynamic Characteristics And Stability Criteria - Elektro-Automatik EL 9080-170 B Betriebsanleitung

See the diagrams below for clarification.
2500W
Peak power
2000W
1500W
1000W
0s 40s 80s
2500W
2000W
Derating @ 25°C
1500W
1000W
Derating @ 40°C
0s 80s
...
3.2.5

Dynamic characteristics and stability criteria

The electronic load is characterised by short rise and fall times of the current, which are achieved by a high band-
width of the internal regulation circuit.
In case of testing sources with own regulation circuits at the load, like for example power supplies, a regulation
instability may occur. This instability is caused if the complete system (feeding source and electronic load) has too
little phase and gain margin at certain frequencies. 180 ° phase shift at > 0dB amplification fulfils the condition for
an oscillation and results in instability. The same can occur when using sources without own regulation circuit (eg.
batteries), if the connection cables are highly inductive or inductive-capacitive.
The instability is not caused by a malfunction of the load, but by the behaviour of the complete system. An improve-
ment of the phase and gain margin can solve this. In practice, a capacity is directly connected to the DC input of
the load. The value to achieve the expected result is not defined and has to be found out. We recommend:
80 V models: 1000 μF....4700 μF
200 V models: 100 μF...470 μF
360 V models: 68 μF...220 μF
500 V models: 47 μF...150 μF
750 V models: 22 μF...100 μF
EA Elektro-Automatik GmbH
Helmholtzstr. 31-37 • 41747 Viersen
Germany
Steady power
210s
...
210s
Fon: +49 2162 / 3785-0
Fax: +49 2162 / 16230
Principle derating progression, depicted on the example of a
2400 W power stage. Models of this series can have several
power stages, which not necessarily start derating at the same
time.
The peak power is absorbed by the load device for a time x,
until derating starts. After the start of derating, the max. power
of the load will settle around the point of steady power. The
momentary true value of steady power can only be read from
the device's actual power value (display or via interface). In
case the ambient temperature rises, the derating will continue.
Derating progression after a cold start of the device at 25°C
(blue) and 40°C (green) ambient temperature.
The temporal progression shows that the peak power at 40°C
is only available for a short time before derating starts. At this
ambient temperature, the steady power will settle at a lower
value than with 25°C.
www.elektroautomatik.de
ea1974@elektroautomatik.de
EL 9000 B Series
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