Current Limit Board; Auxiliary Power Supply - Ametek i Series User Manual

User Manual

5.4 Current Limit Board

The current limit board, A6, receives the oscillator signal and passes it through an amplifier
whose gain is controlled by a signal from the overcurrent circuit. The overcurrent circuit senses
the rms value of the current. If the load current exceeds the programmed value the output of this
sensing circuit reduces the output of the oscillator amplifier. The output of the unit then becomes
a constant current output, with the output voltage dropping as the load increases.
When two or three units are connected as a single phase system the MRA output from the
master oscillator amplifier drives all the power amplifiers over the system interface cable.
An overcurrent condition on any amplifier will act to reduce the output voltage and put the entire
system into the constant current mode.

5.5 Auxiliary Power Supply

The auxiliary power supply is mounted on the DC-DC power board. This assembly generates
nine low voltage outputs. These outputs from the auxiliary power supply provide logic power to
all the modules.
a) +/- 18V to the AC logic board and the oscillator.
b) +8V to the oscillator.
c) + 15V to the DC-DC converter.
d) Three + 18V supplies to the AC power amplifier gate drives.
e) +24V for the fan and relay power.
f) +8V for the digital front panel meter or GPIB/RS232 board.
All the supplies a), b) and e) have a common ground. The supplies in c) and d) are all isolated
from each other and from a), b) and e). LED‟s on the AC logic board and the AC power board are
lit when each output is in regulation. If an overload condition causes the output to drop more
than 10% or the output has failed, the corresponding LED will extinguish. This feature is helpful
in troubleshooting the unit. See Service section 7.
i Series / iX Series 105