Critique Requested for 11 Pound Water Cooled VFD Motor in Testing on 2 x 72 Grinder

Quick update. Following many things that I learned during this thread I dug into the operators manual that came with the VFD. I had up to this point been using it at factory default settings. Not realizing that it was in fact a very capable and adjustable unit that will run a wide variety of motors. I had thought it was specific to the motor that it came with. NOT SO. After reading the manual and understanding what setting I needed to use for this motor I went out today to check the setup and make adjustments if required. I was going for the Hi Torque settings that the manual specified. First turned on the VFD and selected RPM display mode which I had not known about before. Then I cranked it to full and to my suprise the motor was only doing 12,000 rpm not 24,000 rpm like i have thought for the past 6 weeks of testing and grinding more than 30 blanks. The whole time I was running at half speed max. So the whole time I thought I was at 7000 sfpm I was only at 3500 sfpm. What the heck?! It rocked at half speed. So I made the adjustment to the settings to deliver the full rated 24,000 rpm. WOW! While programming I looked at the torque compensation settings which were at 0.1 volts each. For high torque I moved these to the recommended 9 volts at .05hz and 24 volts at 2.5hz. I ran it the motor up to speed to observe the amps which were well under 2 amps with only the belt load. Then I pushed a blank very very hard into the belt to see what the amps would do. They climbed to around 4 amps under a freehand load that no one would likely be applying without a bevel guide to maintain blank control. The motor is rated for 10 amps so there is a good amount of room remaining. The motor will drive the belt a literally inches per minute with enough torque to perform very detailed slow removal. I have not observed this capability in other drives where they are able to run so slow. Then without anything other than turning the knob it will run 7000 sfpm like a monster and everything in between. No that I have learned that there is much more power available than I thought before I will do some more hard grinding and running to see if I run up against any limitations in performance or durability of the system. There is also a slip compensation mode that I will experiment with. It is described as being used to allow the motor to maintain shaft rpm while under heavy load. Very excited by this possibility. I did experience some rpm drop during the previous testing under factory default settings. There was a comment that it might possibly be loosing 20-30% rpm when under load. I will test this to see what can be achieved. Planning another series of videos to demonstrate the rpm and belt speed range, torque performance, amp draw at various loads and speeds, rpm holding ability under load.

 

It sounded much louder when I first set it but I had not ear protection on then and did not spend much time with it. More testing seems to indicate that the rpm was already at 24,000 even though the vfd showed 12,000 rpm. the manual is difficult to interpret. I was thinking the VFD was reading actual spindle rpm. But am now thinking that the rpm display may be just motor rated rpm and is displayed in relation to the hz and not feedback from actual spindle. The torque settings did make a nice difference on the lower speeds. I was pretty excited for a bit when it seemed to indicate I had been running at half speed and it sounded much faster without ear protection. I am still impressed with its performance so far. I added a DRO to my bevel guide recently and have also been learning how to use this.