Rockwell Automation 20P PowerFlex Digital DC Drive - Manual (Page 266)

266 Rockwell Automation Publication 20P-UM001I-EN-P - February 2013
Appendix C Application Notes
Armature Voltage Feedback
When armature voltage feedback is configured, Par 162 [Max Feedback Spd]
must be set to the motor base speed (rpm) value associated with Par 175 [Rated
Motor Volt].
DC Analog Tachometer Feedback
When DC tachometer feedback is configured (Par 414 [Fdbk Device Type] = 2
“DC Tach”), Par 162 [Max Feedback Spd] must be set to the rpm value indicated
by the maximum tachometer input voltage as determined by DIP switch S4 on
the control board (see DIP Switch and Jumper Settings on page
72 ). To maximize
the feedback speed resolution, Par 562 [Anlg Tach Gain] can be used to scale the
voltage setting selected with DIP switch S4 to Par 162 [Max Feedback Spd].
Par 562 [Anlg Tach Gain] = (S4 Maximum DC Input Voltage) x (1000 rpm/
volts Tach Voltage) / Par 45 [Max Ref Speed].
Encoder Feedback
When encoder feedback is configured, it has the same limitations as above except
that no scaling or switch setting is needed because Par 169 [Encoder PPR] is used
instead.
See Speed Feedback on page 269 for more information on setting parameters 162
[Max Speed Feedback] and 169 [Encoder PPR]. Note that setting Par 458
[SpdReg FB Bypass] = 1 “Enabled” is not permitted when field weakening is
enabled (Par 469 [Field Mode Sel] - 1 “Field Weaken”) with a DC Contactor,
unless armature voltage feedback terminals A1 and A2 are connected to motor
terminals A1 and A2, respectively.
Drive Reference and Feedback Scaling Examples
The examples below are based on the following data:
• 500V motor, with base speed = 1750 rpm
• Weakened spd = 2500 rpm
• Weakened ratio = 70% (1750/2500 = 0.7)
• 50V / 1000 rpm tachometer
• 240 ppr encoder
• 7500 fpm application (field weakened or gear-in speed)
Examples 2, 3, and 4 indicate how the value of Par 162 [Max Speed Feedback] is
derived from the required analog tachometer hardware scaling set by DIP switch
S4.