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View Full Version : Can Anyone Provide A Technical Explanation Of How Nova's DVR Motors Work ?



RoyG
14th December 2015, 10:59 AM
Greetings,

I own a Nova 3000 DVR lathe, and I've just bought a used DVR XP that I'll take delivery of next week. I plan to use the DVR XP as a bowl lathe, and dedicate the old 3000 DVR (as it has now been extended to take ~1.2 meters between centres) for long spindle turning work.

As a curious person, I'm always interested in knowing how the machinery that I own actually works - it makes things much easier to diagnose when something goes wrong with the machine. In Teknatool's own documentation, there is only a very simplistic explanation of what the DVR (Digital Variable Reluctance) motor is. A call to Teknatool's telephone support line gave me only a repeat of the marketing blurb that is in their documentation and on their web site - plus the statement that "some parts of the DVR Motors are patent protected".

From examining the parts breakdown diagrams for the DVR Motor, the rotor apparently has permanent magnets embedded in it, and no brushes or wiring. The field coils are only drawn as a basic sketch in the parts diagram, so there's not much to be gained there. From that information, I don't think that it can be a 3 Phase AC Motor with a VFD driving it. I'm guessing that it might be a brushless DC Motor with multiple field coil poles, driven by pulse width modulation.

But the brushless DC Motor explanation doesn't seem to account for some of the additional features, such as the fact that at low speeds (e.g. 200 - 300 RPM), when you place the cutting tool onto the work piece, and load the motor up, you can hear the motor sound change, and the speed remains constant. And, on the two occasions when I've had a bad catch, the DVR Motor instantly shut down, so there must be some sensing involved to determine that there was a catch.

So, can anyone with a technical background in electric motors and/or electric motor speed control technology, provide a technical explanation of how Nova's DVR Motors work ?

Thanks,

RoyG

snowyskiesau
14th December 2015, 11:17 AM
Does this help?
dvrsmartmotor.com (http://www.dvrsmartmotor.com/technology.html)

There's a brief outline of reluctance motors on Wikipedia (https://en.wikipedia.org/wiki/Reluctance_motor).

RoyG
14th December 2015, 12:17 PM
Many thanks for those two links. I'd previously done a lot of Googling looking for these answers, and hadn't found these two links.

Again, Many thanks,

RoyG

wheelinround
14th December 2015, 02:55 PM
Roy I maybe shot down here by DVR XP owners but make sure that power supply is surge protected. I have read not so much on this forum but of others who have had blown motherboards due to possible electrical strikes. Some of these possibly took place during electrical work being carried out by Power Co's in the street or by storm activity when no one was home. As we know any plugged in item even if turned of can still get a surge, 2 sound systems gone, one TV a few PC's of friends.

RoyG
15th December 2015, 09:08 AM
Roy I maybe shot down here by DVR XP owners but make sure that power supply is surge protected. I have read not so much on this forum but of others who have had blown motherboards due to possible electrical strikes. Some of these possibly took place during electrical work being carried out by Power Co's in the street or by storm activity when no one was home. As we know any plugged in item even if turned of can still get a surge, 2 sound systems gone, one TV a few PC's of friends.

You definitely won't be shot down by me for recommending the use of surge protectors !

As a result of having had a lot of electronic equipment in my home killed by one power surge when a nearby transformer decided to do a Chernobyl impersonation, I am now a stickler for surge protecting all of my electronic gear. When my DVR lathe developed a fault a year or so ago, I contacted Tecknatool Support about the error message I was getting on the lathe occasionally, and once they told me how to fix that minor problem (dust on one of the sensors), the support person also advised me to make sure that I always run the DVR Lathe through a good quality surge protector, and always unplug it from the wall when not in use (even if it's connected to a surge protector).

I use Monster brand surge protectors (http://www.harveynorman.com.au/tv-blu-ray-home-theatre/tv-accessories/power-surge-protectors/monster-single-surge-protection.html) - one on each of the DVR Lathes, and on the Computer and AV gear. The Monster surge protectors that I use have a 1,000 Joule rating, and once one or more surges have exceeded the 1,000 Joules, a LED lights up, and a beeper starts going off, indicating that the device is no longer able to provide surge protection and needs to be replaced. Since I bought mine, newer ones have come out with even higher Joule ratings.

Most of the surge protectors around (e.g. most Belkin surge protectors), are only rated at 300 Joules or less, which means that it won't take much of a surge to render them useless. As all of these surge protectors will continue to supply power to the connected device after the surge protection circuit has been "exhausted", you need to buy surge protectors that have warning lights and/or beepers that warn when the surge protection feature had been surged one too many times, and needs replacing. Also, surges can occur on either the Active, Neutral, or Earth wires, so it's important to use a surge protector that monitors all three wires. Many surge protectors on the market only monitor for surges on the Active wire.

Thanks,

RoyG