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Direct current IdCmd
#1
Hello,
I have some questions concerned the direct current Motor[].IdCmd:
- What is the role of Motor[].IdCmd ?
- What is its impact in case of Open-loop or Close-loop ?
- As I know, the command "out" injects the percent of the current Motor[].MaxDac. In the attached image, just Open-loop part, where this "out" current is injected ? What is the impact of Motor[].IdCmd in this case ?
- In the same image, what's the use of Motor[].IdCmd in case of Close-loop because normally the Motor[].IqCmd adjusts all.
Thanks
Xuan


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#2
Hi,

Motor[x].IdCmd represents the "direct current" component for commutating a motor. It is also referred to as the rotor magnetization current. It is required for direct microstepping.

Motor[x].IqCmd in the case of direct microstepping simply acts as a velocity command. It's proportional to velocity. It is usually very small, so does not contribute much to the total current applied to the motor.

Direct microstepping (open loop) is effectively locking the rotor into phase with the stator pole configuration throughout its revolution. IdCmd specifies the current applied as this occurs.

The total current command is the vectorial magnitude sqrt(IdCmd*IdCmd + IqCmd*IqCmd).

In closed-loop stepper, set IdCmd = 0 and the entire current command comes from IqCmd.
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#3
(06-02-2015, 10:18 AM)CharlesP Wrote: Hi,

Motor[x].IdCmd represents the "direct current" component for commutating a motor. It is also referred to as the rotor magnetization current. It is required for direct microstepping.

Motor[x].IqCmd in the case of direct microstepping simply acts as a velocity command. It's proportional to velocity. It is usually very small, so does not contribute much to the total current applied to the motor.

Direct microstepping (open loop) is effectively locking the rotor into phase with the stator pole configuration throughout its revolution. IdCmd specifies the current applied as this occurs.

The total current command is the vectorial magnitude sqrt(IdCmd*IdCmd + IqCmd*IqCmd).

In closed-loop stepper, set IdCmd = 0 and the entire current command comes from IqCmd.

Do you have a detailled scheme like this image but in case of fully Closed-loop ?
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#4
If you search in the ppmac user's manual for idcmd you will find quite a lot of information on what this parameter does. It might not directly answer your specific question exactly as you has asked it but I think after reading about it you will have enough information to understand this parameter.
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#5
The diagram on page 247 of the Power PMAC User Manual applies when doing fully closed-loop stepper control, except that the C phase output to the motor is not used, since it's a stepper motor, not a 3-phase motor.
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