Delta MCS-600 Power Shelf
Installation, Operations and
Maintenance Manual
REV.: 03
3-5
Customer Specification Confidential
Current limit adjustment is made by turning the CL variable resistor with the digital multimeter
probes in the I+, I- test points. This current limit is set at the factory. The factory setting is
always the maximum value of 110%. For a 10-Amp rectifier, the computation for the current limit
is 1.1
×
10=11 Amps.
The following adjustment procedure is for reference only:
1.
At the rectifier, place the digital multimeter probes in the I+, I- test points.
2.
Place a small screwdriver in the CL adjustment point.
3. Turn the variable resistor counterclockwise to increase the value. Turn the variable
resistor clockwise to decrease the current limit value.
3.4 System Alarm
During an alarm condition, the faulty rectifier illuminates its RFA light on the front panel. The rectifier fail
alarm signal is sent to the ALU, which processes the alarm, closes the RFA alarm contacts, and lights the alarm
LEDs.
3.5 PSU Block Diagram
Refer to Figure 8.
3.6 PSU Operating Principle
After applying the incoming line voltage to the rectifier, current is applied to the EMI filter and circulates
through protection components such as the AC circuit breaker and the fuse. The major functions of the
protection devices are to prevent the rectifier from being damaged by surge voltage, to efficiently reduce the
noise of differential mode and common mode, to eliminate the high frequency noise from input current, and to
prevent noise reverse to the source circuit.
The AC input voltage is rectified and converted to a 400 VDC bus through a PFC boost stage. This PFC stage
maintains the Power Factor at >.99 and the Total Harmonic Distortion (THD) at <5%.
The 400 VDC bus voltage is modulated at a frequency higher than 75 KHz and stepped down through a
transformer. Output of this transformer is rectified and filtered to provide the output DC voltage.
