The math is more complex for 3 phase, that's for sure you are right about. Read your VFD specification once again, that is if you have one... Anyway, it is pretty obvious that the 1.5kW Rexroth VFD (1K50 model) I am waiting for is specified to be able to provide an output current of 6.1A at 240V and if you run that VFD on single phase 240V it will require 13.5A. Now, since the efficiency of the VFD (this specific VFD) 95% the 6.1A simply must be per phase, it can NOT be total output because where is the rest of the current gone in that case? 95% 13.5A is 12.825A, so about 0.6A is heat and loss, but what about the other missing 6.725A between input and output?
Attachment 318900
It is pretty obvious that either Bosch is totally wrong and not know enough about their own VFD or you are missing something, because Bosch clearly claims that the input current for my VFD is 13.5A at 240V. Of course, before you correct me, I know, my mains is 230V, so that input current need will be increased to about 14.1A
You might have an education and experience in this, but if that is true than you should educate us and explain why am I wrong and why Bosch is wrong in their specification, not just emphasize what I don't keep a secret, that I am still waiting for my VFD to arrive, which is why my discussion is still purely theoretical. That comment, which you emphasized with all those stars, are meant to be read as "I am still waiting for my VFD, so I can't measure anything, and since I have never had a VFD before, I don't have any experience with one." That's all. It does not mean I don't have an education in this, even if my electrical education took place more than 40 years ago, I hardly think Ohms law have changed...
I don't understand why you mention Y connection at all. The VFDs we are discussing, and the motors we use as CNC spindle motors are all delta connected. The fourth wire is protective earth, NOT neutral. So please, don't increase the confusion here, because if you really have education in this than you should know this.
Also keep in mind that efficiency of a motor is not interesting because REGARDLESS of that, the MAXIMUM current of the VFD is already specified by the manufacturer of the VFD. We are not trying to find a VFD for a given motor with a given, fixed power here, in which case you must look at that motor efficiency, but we discuss a VFD with an already specified parameter.
I'd appreciate if you'd use your education and explained why am I wrong, not just claim that you are right. Ripping apart my answer and empasize/twist words is pretty rude in my opinion. I have no problems in being proven wrong, but claiming that
"I do have education and experience in this." is a pretty lame proof. Sorry.
In short, if I am wrong please tell me why. Not that you know better, because that's not very educative.