User's Manual

PMAC User Manual
14 Getting Started with PMAC
Commutation Encoder
The encoder register used for commutation feedback must be specified with Ix83. The default value of
Ix83 specifies Encoder 2x-1; e.g. ENC1 for Motor 1, ENC3 for Motor 2, and ENC15 for Motor 8. The
actual value of Ix83 is the address of the phase position register for that encoder. For ENC1 (Motor 1), this
value is 49153 ($C001). If setting up a PMAC-commutated Motor 1 using ENC1, make sure I183 is set
equal to 49153 ($C001).
Counts per Commutation Cycle
Next, determine the number of encoder counts per commutation cycle (per pole pair). I900 defines an
encoder count here (1, 2, or 4 counts per line). For instance, if using a 2500 line per revolution encoder
with x4 decode and a 4-pole motor, the calculation would be: (2500 lines/rev) * (4 counts/line) / (2 pole-
pairs/rev) = 5000 counts/pole-pair.
If this value is an integer, set I170 to 1, and set I171 to the value. If the value is not an integer (for
example, a 6-pole motor and a 1024-line encoder), figure out the integer multiplier required to make it an
integer (usually 3). In this case, set I170 to the multiplier, and I171 to the multiplied integer value.
Angle Between Phases
If it is a 3-phase motor, set I172 to 85. This tells PMAC that the two phases are 85/256 (1/3) cycle apart.
This may be changed later to 171 if the polarity of the signals are wrong. If it is a 4-phase motor, set I172
to 64 (64/256 = 1/4); the may be changed later to 192.
Phase Search Parameters
Now, if using a brushless DC (synchronous AC) motor, establish the parameters for the power-up phase-
finding search. Initially, set I173 (the magnitude of the phase-finding output) to 8192 which is one-quarter
of full output. Next, set I174 (the time for each half of the phase-finding routine) to five servo cycles.
These can be optimized later. Now make sure the induction motor parameters I177 and I178 are set to 0, so
PMAC will not think this is an induction motor.
Slip Gain and Magnetization Current
If using an AC induction motor, do not worry about power-up phase finding. Set I173 and I174 to 0. Also,
set I177 (magnetization current) and I178 (slip gain). Initially, set I177 to 3200 (1/10 full current) and I178
to 2500 (for a low-slip motor) or 5000 (for a high-slip motor). These can be optimized later. The fact that
I178 is greater than zero prevents a phasing search, so I173 and I174 are irrelevant.
For Motors Not Commutated By PMAC
If PMAC is not performing the commutation for the motor, set Ix01 to 0 so that the commutation routines
are disabled and only one analog output is used. In the example using motor 1, set I101 to 0. This is the
default.
DAC Output Address
If not commutating from PMAC, Ix02 must be set to the register address of the single analog output used to
command the amplifier. Define the output register address for motor #1 using I102. In order to send the
motor 1 output command to the DAC1 pin connected, set I102 address $C003 (49155 decimal). This is the
default value. If the amplifier is expecting sign and magnitude input, set I102 to $1C003 instead.
For All Types of Motors
Regardless of whether PMAC is commutating the motor or not, several variable values must be established
to tell PMAC where to get its servo loop information.
Position-Loop (Load) Feedback Address
Variable Ix03 defines the register to be used for the position-loop servo feedback. Typically, this reads a
processed encoder value from what is known as the encoder conversion table. To have motor 1 read the
processed input from Encoder 1, I103 must be set to 1824 ($720). This should be the value preset at the
factory.