Delta Tau GEO MACRO DRIVE User Manual download pdf (Page 97)

Geo MACRO Drive User and Reference Manual

Setting Up Turbo Motor Operation 85

Instructions for Direct-PWM Control of Brush Motors

WARNING:

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

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

both drive and motor.

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=I6800/50 M104=-I6800/50 M107=0 ; A pos, B neg, C zero

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 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 received

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

Since the M-Variables are defined as +/-32,768 for 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, usually which is about 1/3 of the instantaneous limit. If well below the

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

M102=I7000/10 M104=-I7000/10 M107=0 ; 10% of maximum

PWM/ADC Phase Match

Command values from Turbo PMAC’s Phase A PWM outputs should cause a roughly proportionate

response of one sign or the other on Turbo PMAC’s Phase A ADC input (whatever the phase is named in

the motor and drive). The same is true for Phase B.

If no response is received on either phase, re-check the entire setup, including:

• Is the drive properly wired to Turbo PMAC, either directly or through an interface board?

• Is the motor properly connected to the drive?

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

• Is the interface board properly powered?

• Is the amplifier enabled (M114=1 on Turbo PMAC and indicator ON at the drive)?

• Is the amplifier in fault condition? If so, why?

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

properly. 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 and checking which

ADC responds to which phase command. If there is not a proper match, change the wiring between

Turbo PMAC 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. However, an induction motor will not keep a holding torque

indefinitely at the new location.

Current Loop Polarity Check

Observe the signs of the ADC register values in M105 and M106. These two values should be of

approximately the same magnitude, and must be of the opposite sign from each other. (Again, remember

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Delta Tau GEO MACRO DRIVE User Manual Page 97

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