Vinyl Asylum Welcome Licorice Pizza (LP) lovers! Setup guides and Vinyl FAQ.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Vinyl Asylum ]

---

[ Alert Moderator ]

---

RE: Motor controller....IT'S ALIVE!!!

Posted by twystd (A) on April 16, 2016 at 02:07:03

In Reply to: RE: Motor controller....IT'S ALIVE!!! posted by coffee-phil on April 16, 2016 at 00:14:28:

Phil, my understanding of all this isn't very complete, remember what little technical knowledge I have is pretty much self taught, and my learning is an ongoing process. From what I understand, and it may be wrong, is that with the faking capacitor, it mimics a second phase, and that this phase is 180 degrees out, and as such, there is some cogging going on with that approach. Doesn't this phase angle also change with frequency? In this case, with three phases, they are 120 degrees from each other, and there is less of this cogging effect. BTW, with this generator we can change the individual phase angles if we want, and vary the signal amplitude to a certain degree (not as much as I would like), in order to change the output voltage.

You may want to see Pheonixengr's very interesting post discussing this among other things, about a nice little Japanese 3 phase motor he was working with, and a new 3 phase VFD he developed for it, see link below. He seems to think that a 3 phase supply has big advantages, less cogging only one of them. He has the advantage of having low enough power (12 watt) and low enough voltage (24V) that he doesn't need a transformer to step it up from the sand amps. Dealing with the 30 watts and 120V or so, like we have to with the Papst motor, makes it more difficult.

As far as the need for a resistor or not in the load, I don't think it has much to do with the phase angle, as much as it does the temporary short circuit the amp would see, and the resulting current inrush, until the core of the transformer magnetizes. It's only when the core of the transformer magnetizes that the load of the motor is reflected back to the amp. This seems like it would happen even with just a single phase. Anytime you have a solid state amp, with an extremely low DCR load, like in a transformer primary, with a big step up, bad stuff happens. Solid state amps don't like to see a short circuit even for extremely short periods of time. From what I hear, they either fry, or shut themselves down from overload protection.

Seems to me in most cases some resistance has to be loading these amps, I'm reducing that load in the near future from 8.2 to 4 ohms. I used 8.2 ohms as that was what I had laying around. You can see my posts to Penguin in this thread for more on this, and other changes I have in store, BTW how are you on thermistors? Looks like I'll have to use them on the 120V line power inputs on the supplies, and don't know how to spec them for that ap. Maybe you, or someone else reading this, could save me some research on that.

BTW any suggestions, and or a design review process is very welcome by me, improvements or reasonable alternatives would be greatly appreciated. As a matter of fact, I have several changes I'm working on now, and when I get the parts in, and have time to evaluate, I will post.

twystd

• http://www.audioasylum.com/audio/vinyl/messages/112/1129031.   (Open in New Window)

This post is made possible by the generous support of people like you and our sponsors:

Sonic Craft

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---