Rockwell Automation 1902 Syncpro II - Manual (Page 34)

36 Rockwell Automation Publication 1902-IN001B-EN-E - April 2013
Chapter 4 Setup and Commissioning
Table 1 - Feedback Resistor Values • Synchronous Field Feedback Board
Motor induced currents will cause a voltage to be produced across the
synchronous motor starter field discharge resistor. This voltage is connected to
the feedback resistors and the tap to be selected on these resistors is dependent on
this voltage level. For example, if the discharge resistor value is 20
Ω and the
induced currents are 30 A at 0 speed and 18 A at 95% speed, then the induced
voltage seen by the feedback resistors will range from 600V (0 speed) to 360V
(95% speed). The selection would then be 10 k
Ω on each of the two resistors.
In the event that the induced voltage proves to be higher than allowed by the
chart, it will be necessary to tap the field discharge resistor at a point which will
allow the value to fall within the chart. Contact Rockwell Automation for
assistance at 1-519-740-4790.
Commissioning
1. Complete and verify that the setup procedures (see
page 33 ) have been
completed. This should include verifying that the parameters programmed
into the SyncPro II are appropriate for the motor. See
Chapter 5 for
further details on programming.
2. Verify that the SyncPro II has been wired into the motor starter circuit as
indicated by the wiring diagram.
3. Remove the wire from the Field Contactor Relay (FCR) coil either at the
I/O point (0:0/2) or at the FCR coil itself. Tie back and insulate the wire
so that it cannot accidentally short out to ground or another electrical
point. This will disable the field contactor so that the starter will not
attempt to synchronize.
RF1/RF2 Resistance (K Ω) (1)
(1) Resistance value is per resistor (two required).
Usable Voltage Range
Lower Limit Upper Limit
2.5 80 160
5 160 320
7.5 230 480
10 320 640
12.5 400 800
15 490 950
17.5 560 1100
20 640 1300
IMPORTANT The contactor must be disabled in this manner rather than removing
the field cables from the contactor. The discharge path through the
discharge resistor must be maintained; otherwise, a voltage high
enough to damage the field insulation will occur at the open field
windings. This is similar to the effect which occurs if a current
transformer secondary winding is left open circuited.