Rockwell Automation 1902 Syncpro II - Manual (Page 31)

Rockwell Automation Publication 1902-IN001B-EN-E - April 2013 33
Chapter
4
Setup and Commissioning
Setup Check the following components of the SyncPro II once it has been installed.
R
F
1 & R
F
2 Resistor Setup
The synchronous motor field discharge resistor feedback resistors (RF1, RF2) are
necessary to attenuate the induced voltage waveform which appears across the
field discharge resistor during starting (
Figure 11 ). The resistors (RF1, RF2)
reduce the voltage which is seen at the terminals of the analog/digital pulse
converter to a level which is acceptable to the optoisolators on the board.
Guidelines for resistor settings are contained in
Table 1 on page 36 .
The resistance value shown is the amount of resistance which is required on each
lead which is connected to the A/D pulse board (F1, F2). For example, if the
induced voltage on the discharge resistor is 1000V at zero speed and 600V at 95%
speed (across the entire discharge resistor), then it is necessary to select taps on
the RF1 and RF2 to provide 20 k
Ω at RF1 and 20 k Ω at RF2.
Figure 10 - Discharge Resistor Installation
These settings must be made prior to any start attempt.