Advanced Energy MDX II User Manual page 73

target when new
target at end of target life (EOTL)
To calculate the operating currents, use
current for new target
current at EOTL
Now you have the voltage range and current range for the target over its useful life. The
voltage and current values for the target when it is new and then at EOTL are plotted on Figure
5-1 on page 5-11. Notice that the impedance at both target stages falls within the boundaries of
tap 4.
You can go a step farther and calculate the impedance for the target at both states by using the
Target Impedance
calculation
Note: If you are specifying a new power supply, you should perform the above step first with
your current equipment. Note that these measurements are accurate only at the power
level used to make them (here, 13.8 kW). Each target and its associated process
parameters produce a unique environment in which the target impedance changes as the
power changes. Therefore, the impedances must be determined for each target/process
combination.
impedance for new target
impedance at EOTL
The impedances are plotted on Figure 5-2 on page 5-12; once again you can see that both
impedances fall within the boundaries of the range available with tap 4. Therefore, selecting
tap 4 enables the power supply to operate throughout the life of the target at a power setting of
13.8 kW.
Example 2
The power supply in this example is an MDXII 15k stand-alone unit, the method of regulation
is power, and the operating level is 13.8 kW. We have assumed typical operating voltages for
both a new target and a target near the end of its useful life (this value is lower than in
Example 1).
5700262-R
780 V
600 V
Current
=
13.8kW
------------------ 17.7A
=
780V
13.8kW
------------------ 23A
=
600V
Target Voltage
----------------------------------- -
=
Target Current
780V
------------- - 44Ω
=
17.7A
600V
------------ - 26Ω
=
23A
Operation Overview
MDXII Power Supplies
Power
--------------------
Voltage
5-9