Parker BD-E Series, Manual

Page: 41 / 48

APPENDIX A. ENCODER SETUP 35
Appendix A. ENCODER SETUP
Introduction
This section is applicable when the BD drive is not used with Digiplan MD Series motors.
BD drives are designed to operate with 3-phase brushless servo motors which have both a
commutation encoder (Hall effect encoder) and an incremental encoder fitted. The commutation
encoder must have Com A leading Com B by 120
°
electrical and Com B leading Com C by 120
°
electrical, and must have the same pole count as the motor. The incremental encoder must
have 512 or 1024 lines, with A+ leading B+ for clockwise (CW) motor rotation. The I+ output is a
high going pulse that occurs when A+ and B+ are high and is shorter than one complete cycle of
A+ (see Table 3-1 waveform diagram).
Commutation
When power is first applied to the drive, the commutation encoder is used to establish a torque
angle of approximately 90
°
electrical, so that 87% smooth motor torque can be achieved
immediately. Once the motor has moved through 180
°
electrical, it will have passed an edge of
Com A, achieving a more accurate setting of the torque angle, allowing 95% torque to be
obtained. Following a complete revolution, the motor will have received an index pulse which
provides the most accurate position information allowing 100% torque to be applied. The index
pulse also acts as a continual check on the electrical position.
Encoder Setup
When setting up the encoders, disconnect the motor cable from the drive, but leave the encoder
cable connected and the drive powered up but de-energised. Select any motor phase, say 'u' in
Figure A-1, and take it to the negative connection of a DC power supply, as shown. Connect the
other two motor phases to the power supply positive connection via power diodes.
+ve
-ve
DC PSU
U phase
Figure A-1. Encoder Set-up Circuit