User Manual – Rev BE AMETEK Programmable Power
MX Series 312
9.11 Option –SNK: Current Sink (AC or DC)
9.11.1 General
This section describes the SNK option available for the MX Series Power Source.
9.11.2 General Description
The –SNK or current sink option enables the MX power source to sink current
from the unit under test. This mode of operation is particularly useful when
testing grid-tied products that feed energy back onto the grid. The ability of the
MX to simulate the grid provides unique opportunities to test the EUT for
immunity to commonly occurring line anomalies like voltage and/or frequency
fluctuations. Typical examples of these types of EUT’s are solar and/or wind
power inverters.
The SNK option requires special amplifiers that have a different control loop
from the standard MX amplifiers. This different control loop ensures greater
stability under regenerative load conditions. Due to this modified characteristic
however, the upper frequency limit of an MX configured with the –SNK option is
reduced to 500Hz from the standard 819Hz.
MX units without the SNK will generate an error message if more than 20% of
available power (per phase) is regenerated by the load. It will shut off if the
negative power reaches 30% of available power.
Regenerative Mode of operation The MX will automatically operate in
regenerative mode when the Regenerative state is enabled and the measured
power is negative, indicating energy is being fed back into the MX amplifiers. In
this mode of operation, the current limit mode will behave differently than it
does under normal load conditions.
When the absolute value of the current exceeds the regenerative programmable
current limit set point (current limit is set in the REGENERATE CONTROL
screen), the output voltage of the MX will be increased gradually to reduce the
amount of current being fed back. Note that there is no other way for the MX to
limit the current as the current is not generated by the MX itself but rather by
the load (inverter). Consequently, normal current limit operation does not apply
in this mode of operation. The voltage will continue to be raised until the user
set over voltage trip point is reached. This trip level can be set in the
REGENERATE CONTROL screen located under the APPLICATIONS SETUP 2
screen. At this point, and after the delay set by the “DELAY F” parameter is
reached, the AC frequency will be shifted by the amount set in the dFREQ
parameter field. The dFREQ is irrelevant for the DC SNK operation. A
consideration in the AC SNK mode is the fact that most AC inverters will shut
down when detecting a sudden change in frequency. If the frequency shift
(dFREQ) is set to zero however, the output voltage will be dropped to the
under-voltage limit setting (UNDER VOLT) set in the REGENERATE CONTROL
To Next Page
Loading...
Need help?
General
