Power Over Time - Lab.gruppen PLM series Operation Manual

7. Operation and Performance
Load
Impedance 2.0
(ohms)
Max.
Output
2350
power
(Watts)
Table 7.2.2a: Asymmetrical load power ratings

7.2.3 Power over time

Power ratings given above are applicable for PLMs running at these levels for a period of 60 minutes. Due
to thermal considerations in the power supply and elsewhere, it is possible to draw higher power levels for
a shorter period of time. The graph below illustrates, for the example PLM 10000Q, how the rated power
figures are derived and the higher short-term capability.
Peak output voltage at "max power burst"
Figure 7.2.3: Power rating levels over time
Power ratings are based on a "real-life" duty cycle of 25 ms full power every 400 ms. Between bursts, a
lower signal level applies, such that the continuous average power is 1/8th of the rated power.
In reality, when some channels are delivering less than maximum rated power, energy reserves in the PSU
are available to permit other channels to deliver more power. The graph shows the peak output voltage over
time for a continuous sine wave is applied.
If all four channels are driven with the same signal into the same impedance (solid red line), then the rail
voltage (dotted red line) will drop faster than when two channels are delivering "max power" (solid blue line)
and two channels are delivering "half power" (solid orange line). This is termed asymmetric loading. The rail
voltage for this is the dotted blue line.
It can be seen that higher power output is available for 25 ms bursts with asymmetric loading.
26
PLM Series Operation Manual rev 1.1.3
2.7 4 8
2900 2400 1200
for PLM 10000Q
Load
16 Impedance
(ohms)
Max.
Output
660
power
(Watts)
Table 7.2.2b: Asymmetrical load power ratings
2.0 2.7 4 8
7500 6300 4400 2300
for PLM 14000
16
1150