Delta Tau PMAC2 PCI User Manual download pdf (Page 35)

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PMAC2 User Manual

Setting Up PMAC2 for Direct PWM Control 27

PWM Output and ADC Input Connection

First enable the amp, then apply a very small positive command value to Phase A and a very small

negative command value to Phase B with the on-line commands:

M114=1 ; Enable amplifier

M102=I900/50 M104=-I900/50 M107=0 ; A positive, B negative, C zero

Caution:

Make sure before any PWM commands are applied to the drive and motor in this

fashion that the resulting current levels are within the continuous current rating of

both drive and motor.

This provides a command at 2% of full voltage into the motor; this should be well within the continuous

current rating of both drive and motor. It is always a good idea to make the sum of these commands equal

to zero so as not to put a net DC voltage on the motor; putting all three commands on one line causes the

changes to happen virtually instantaneously.

With power applied to the drive and the amplifier enabled (M114=1), current readings should be in the

ADC registers as shown by the M-variables M105 and M106 in the Watch window.

As we have defined the M-variables, +/-32,768 is full current range, which should correspond

approximately to the instantaneous current limit. Make sure that the value read does not exceed the

continuous current limit, which is usually about 1/3 of the instantaneous limit. If it is well below the

continuous current limit, increase the voltage command to 5% to 10% of maximum. For example:

M102=I900/10 M104=-I900/10 M107=0 10% of maximum

PWM/ADC Phase Match

Command values from PMAC2's Phase A PWM outputs should cause a roughly proportionate response

of one sign or the other on PMAC2’s Phase A ADC input (whatever the phase is named in the motor and

drive). The same is true for Phase B.

If a response is not received on either phase, re-check the entire setup, including:

1. Is the drive properly wired to PMAC2, either directly or through an interface board?

2. Is the motor properly connected to the drive?

3. Is the drive properly powered, both the power stage and the input stage?

4. Is the interface board properly powered?

5. Is the amplifier enabled (M114=1 on PMAC2 and indicator ON at the drive)?

6. Is the amplifier in fault condition? If so, why?

If an ADC response is received on one phase only, the phase outputs and inputs may not be properly

matched. For example, the Phase B ADC may be reading current from the phase commanded by the

Phase C PWM output. Confirm this by trying other combinations of commands as shown in the six-step

test below and checking which ADC responds to which phase command. If it is not a proper match,

change the wiring between PMAC2 and the drive. Changing the wiring between drive and motor will not

help here.

Synchronous Motor Stepper Action

With a synchronous motor, this command should cause the motor to lock into a position, at least weakly,

like a stepper motor. This action may be received temporarily on an induction motor, due to temporary

eddy currents created in the rotor.

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Delta Tau PMAC2 PCI User Manual Page 35

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