Well you've got me quite confused.
Are you saying that these spindles are damaged when running at slower speeds than max RPM??
How do you run the spindle at variable speeds without changing its main frequency or as the manual states "operating frequency"? I cannot run the spindle at max RPM and have no plans on doing so. That would require my CNC to feed far faster than it is capable of.
I have not found where it says PD003 needs to be set to the maximum. My manual says that the "operating frequency" is set by 1 of 3 sources, the digital operator, external terminals, or MODBUS:
1. PD002 is the "source of the operating frequency". This can be set to the "digital operator" or PD003 (PD002 = 0), "external terminals" (PD002 = 1), or MODBUS (PD002 = 3).
2. "In the digital operator mode, the inverter will run at the set value of PD003. During running, the operating frequency can be changed by pressing UP or DOWN."
3. "During multi-speed running, the main frequency is taken as the frequency of Speed 1."
In multi-speed mode PD003 is taken as Speed 1, speeds 2-16 are set with PD086-PD100
4. "In external control multi-speed mode, if PD002 is set to 1, i.e. given by an external terminal, Speed 1 will be given by the analog of the external terminal."
The analog voltage or amps (range set by PD070) determines the operating frequency
In all 3 modes the "operating frequency" is adjustable during running - intentionally. I cannot find where it says that PD003 must be set to the max frequency of the motor (this is what PD004 is, "This parameter must be set according to the rated frequency" and "do not change the set value of base frequency at will"). Instead, it describes how the VFD runs a variable speed motor and how all three modes adjust the "operating frequency" during running.
If I'm using a pot in external terminal mode, the operating frequency will be set by the analog input voltage/amps set by PD070. Therefore, even if PD003 is set to 400, the VFD will be operating at the frequency set by the analog input, and if this is less then the max voltage in PD070, it will be less than 400. In my case, I'm never going to just turn the pot to max (5V) and leave it there, because that is too fast for my machine (24,000 RPM) so it will be operating at less than 400 Hz.
Likewise, in the furture, if I'm using MODBUS, I can set the operating frequency with speeds 1-16, PD086-PD100 and PD003. And each speed will be set a lower frequency than 400, except for maybe Speed 16 which could be the max RPM speed.
Long story short. I need to be able to run the spindle at less than max RPM. If I cannot do this safely and reliably with this spindle. I need to return it.
So I'm very grateful for your help! I definitely feel like I'm missing something important here. I apologize if I'm unintentionally frustrating you!