Author	[Modern View]
Mtjohn 10-31-2012 19:33:47 66.171.17.252 Report to Moderator	We are getting a bigger milling machine that takes three phase power so in need of a phase converter. Finding lots of options and am probably going to go with a rotary. Question is if I oversize the converter will it hurt anything. Thinking of going to about a ten horse converter and this mill is a four horse motor. Reason that I want the bigger converter is I am looking at a bigger lathe 7-10 horse motor and would like to buy only one converter. Another thought is do they make a rotary converter that is also a welder. I used a I think Lincoln welder that was a motor generator combo that was around 400 amps and a very steady arc. It looked alot like a torpedo or bomb shaped. So do they make such a beast and what are the electrical experts thoughts on sizing of converter. Thanks for any ideas or thoughts. [Reply]   [No Email]
huntingreen2day 11-01-2012 22:35:16 75.131.120.19 Report to Moderator	Re: Phase converters in reply to Mtjohn, 10-31-2012 19:33:47   I bought a 15 HP motor at an auction several years ago for $50. About 4 years ago I bought a Leblond 3 phase lathe. Dug out the motor and bought me a control panel from American Rotary for $ 300 plus and it has made an excellent rotary phase converter. A little loud because the motor has a fan on it. [Reply]  [No Email]
Ed The Wine Farmer 11-01-2012 18:26:11 74.47.119.135 Report to Moderator	Re: Phase converters in reply to Mtjohn, 10-31-2012 19:33:47   In 3 phase power, the phase angle is the problem when changing single phase to 3 phase. Think of a equilateral triangle; one in which all 3 sides are equal. If you think of thees three 3 points as a delta or a Y, they are 120 degrees apart. when you change from single to 3 phase, the triangle can change shape. This condition is an out of phase. It will make heat which is not good. You must balance the load with the supply, One way to do this is with a rotary converter. To make this work in a shop with several machines, is to use an amp probe, several relays and capacitors to adjust the load and keep the phase angle at 120. If the converter can not do this, It"s not worth having. Ed [Reply]  [No Email]
JMOR 11-01-2012 11:20:26 72.181.173.171 Report to Moderator	Re: Phase converters in reply to Zachary Hoyt, 10-31-2012 19:33:47   Quoting Removed, click Modern View to seeDon't know where to point you, but I think any lathe work, especially cutting threads for example, where you need instant reverse, will leave you severely disappointed in a VFD. [Reply]  [No Email]
David G 11-01-2012 12:16:55 204.29.138.33 Report to Moderator	Re: Phase converters in reply to JMOR, 11-01-2012 11:20:26   I think you are misinformed about a VFD. A VFD can accelerate as fast as possible, but will limit maximum current to a setting. It will decelerate as fast as possible, but must not overcharge the DC bus doing so, or use an external resistor. A servo is a VFD with feedback. The unit might already have a VFD if it is variable speed. [Reply]  [No Email]
JMOR 11-01-2012 12:28:35 72.181.173.171 Report to Moderator	Re: Phase converters in reply to David G, 11-01-2012 12:16:55   I could be, David, but I see 'qualifiers' here, in "as fast as possible" and "will limit maximum current to a setting" and "but must not overcharge the DC bus", so, then, the question remains, will the 3 phase motor change direction of rotation just as fast when going forward & suddenly slammed to reverse, when powered by a VFD, as it would when powered by Consolidated Edison? [Reply]  [No Email]
JMOR 11-01-2012 10:45:55 72.181.173.171 Report to Moderator	Re: Phase converters in reply to timcasbolt, 10-31-2012 19:33:47   Quoting Removed, click Modern View to seeI would call your understanding correct, since the Phase-A-Matic that I took apart has a capacitor, relay, and a voltage sensing device which controls the relay. That makes it just about like the start circuit in a whole bunch of single phase motor starting circuits. It is using the "potential relay" to switch a capacitor into the circuit between one input leg and the 3rd phase connection of the 3 phase motor, until the voltage passes a fixed threshold on spinning up (5 seconds or less), then cap is switched out & motor runs with the input to 2 of the 3 motor's input lines. [Reply]  [No Email]
NCWayne 11-01-2012 07:47:08 69.40.232.132 Report to Moderator	Re: Phase converters in reply to Mtjohn, 10-31-2012 19:33:47   Ok, as usual alot of guys recommending a VFD. Granted the prices on a VFD have come way down, but they will still ONLY RUN ONE MOTOR AT A TIME which is no different than using a static phase converter, which, by the way, is typically going to be alot cheaper than a VFD. The drawback with a static converter is that it basically allows the driven motor to run as a single phase which results in a loss of aboyt 1/3 of the rated HP. On the other hand a rotary converter can run multiple motors. With them you don't want to size the converter too large or it won't create the necessary voltage for a smaller motor. Case in point Dad bought a large one for his shop. In order to run the smaller 1 HP motors off of it there had to be another, larger motor also running at the same time. He gets away with it due to running a constant run 7.5 HP cair comopressor. The reason he had to get such a big converter though was the starting capability for the compressor, and then it's abilty to run both it, a 5HP lathe motor, and at the same time to have enough left over to run the mill, etc. If your a one man show one piece at a time will probably be all your worried about, but with two of us working the possiblity of two pieces running at the same time had to be taken into account. With that said, do some checking around on the mfgs sites and see what they have avaliable with the capability to start your machine. Pay attention to the details because the way a rotary is designed it will start and run motors with up to X HP, and then run a combination of motors up to a total of X HP. Too, because if the design of a rotary system, each motor that is running is also doing it's part to add to the generation of the third leg. As a result the total load, starting load, etc will basically increase to a degree the motors that are running off the origional phase converter/idler motor. Good luck. [Reply]  [No Email]
Butch(OH) 11-01-2012 11:21:38 70.62.13.146 Report to Moderator	Re: Phase converters in reply to NCWayne, 11-01-2012 07:47:08   All true but a rotory costs some bucks also if purchased new. My 10 HP Rototphase was $1300 10 or 12 years ago. As you said a person's "rotary converter" can possibly be just another machine in the shop started with a static but he has to have two machines. To know what is best in each case a person about has to know how many machines that need 3ph are going to grace the shop, the HP of each and how much the individual can build himself. In any case the VFD get more attractive as they get cheaper. [Reply]  [No Email]
NCWayne 11-01-2012 14:53:49 69.40.232.132 Report to Moderator	Re: Phase converters in reply to Butch(OH), 11-01-2012 11:21:38   Yeah, a rotary bought new is expensive, but they aren't all that hard to build using a three phase motor and a few capacitors. lI just built one using a brand new, TEFC, 10 HP TECO Westinghouse motor bought off Craigs list for $225 and some capacitors and contactors I picked up that were headed to the scrapper. I know I don't have as much invested in mine as some would, but for the cost of a decent motor, and the necessary parts to put one together, it's still way easier and cheaper to build your own converter than to buy one brand new. Too, with a little more research if you build one sized for x ammount of HP and find you need more they can be tied together. In the end I can see the VFD being good in some cases, but for multiple machines you simply can't beat a rotary converter for reliability and life expectancy. [Reply]  [No Email]
buickanddeere 11-01-2012 10:03:39 207.164.79.49 Report to Moderator	Re: Phase converters in reply to NCWayne, 11-01-2012 07:47:08   Three phase equipment operated on single phase has the output reduced to 57.7% of nameplate capacity. [Reply]  [No Email]
NCWayne 11-01-2012 10:21:57 69.40.232.132 Report to Moderator	Re: Phase converters in reply to buickanddeere, 11-01-2012 10:03:39   By single phasing I mean it basically runs as a 220 volt motor, with two actual hot legs doing the work, and the third being manufactured mainly for starting purposes. That said I'm just basing my info on what I've read in relation to the reduction in voltage caused by running a 3 phase motor off of a static converter as stated by a reputible static converter mfg. If they are wrong then I guess they have been making, and marketing their converters for a long time with faulty information without getting caught. Phase a matic site [Reply]  [No Email]
David G 11-01-2012 10:07:29 204.29.138.33 Report to Moderator	Re: Phase converters in reply to buickanddeere, 11-01-2012 10:03:39   You can utilize the full HP of the motor if you oversize the VFD for the loss of the input phase. [Reply]  [No Email]
Mtjohn 11-01-2012 09:17:46 70.198.11.213 Report to Moderator	Re: Phase converters in reply to NCWayne, 11-01-2012 07:47:08   Thanks all for the input. Will look into vfd I see very little info as using them for phase converters mostly speed controll as I am googling them. I really want to be able to utilize the larger mill motor fully as the 2hp one currently using will overheat and need resetting on a heavy cut. Any recommendations on who to talk to about purchase and specs to match up? To my untrained eye it looks like you are derating hp by pulsing the input power. Will need to research as I am not fully understanding how this is getting my three phase. I have heard horror stories about letting the smoke out of static converters and that was why I was leaning rotary. My new mill is variable speed so would not need that capability from converter. [Reply]  [No Email]
David G 11-01-2012 07:05:48 205.215.206.18 Report to Moderator	Re: Phase converters in reply to Mtjohn, 10-31-2012 19:33:47   The thing to remember is VFD's are 90+ efficiency, using 2 motors or phase converter is not. You must oversize the VFD to compensate for the lost phase coming in, but this does not affect the efficiency. They are adjustable to coast or ramp to stop. you must provide adequate external resistors if you want to stop quickly. [Reply]  [No Email]
Bus Driver 11-01-2012 05:19:06 66.226.40.31 Report to Moderator	Re: Phase converters in reply to Mtjohn, 10-31-2012 19:33:47   For most purposes, the VFD will be the better choice. The one limitation of the VFD is that it can serve only one motor at a time. Mine works best with some programming tweaking to better match it to the motor and to my preferences. If going to a different motor of a different size, reprogramming is in order. The programming manual with mine is 183 pages. But the 3 or 4 parameters that I typically change are quickly learned. The VFD offers some advantages over true 3-phase power-- and has some disadvantages. Rotary and static converters offer no advantages over true 3-phase power. [Reply]  [No Email]
Butch(OH) 11-01-2012 05:12:01 70.62.13.146 Report to Moderator	Re: Phase converters in reply to Mtjohn, 10-31-2012 19:33:47   Back when I equipped my shop 15 years ago the price of one VFD would take your breath away let alone 3-4 of them so I installed a big rotary. Times differ today and the VFDs just keep getting cheaper and cheaper. A quick check on Ebay found a 4HP VFD for $133 delivered to your door. As the others said VFD is the way to go today unless you can source the bits to assemble a rotory for close to free. [Reply]  [No Email]
buickanddeere 11-01-2012 04:51:39 207.164.79.49 Report to Moderator	Re: Phase converters in reply to Mtjohn, 10-31-2012 19:33:47   Motor generator welder is a distant cousin to an old time rotary phase converter. At one time there only was rotary converters or single phase motors driving a three phase alternator. Today we can have better control, at less cost and have higher efficiency with a VFD. [Reply]  [No Email]
JMOR 10-31-2012 19:56:44 72.181.173.171 Report to Moderator	Re: Phase converters in reply to LOU from Wi., 10-31-2012 19:33:47   Quoting Removed, click Modern View to seeOn a lathe, when instantly reverse the direction, what is that VFD going to do? [Reply]  [No Email]
David G 10-31-2012 20:09:11 205.215.206.18 Report to Moderator	Re: Phase converters in reply to JMOR, 10-31-2012 19:56:44   The VFD will stop it, then start it in the other direction. You can set them to coast or use dynamic braking. [Reply]  [No Email]
Stephen Newell 10-31-2012 19:43:26 63.25.74.211 Report to Moderator	Re: Phase converters in reply to Mtjohn, 10-31-2012 19:33:47   Running a phase converter is running two big motors and you need a bigger motor on the converter than the machine. The converters are expensive and expensive to operate. The VFD or variable frequency drive is the way to go. Phase converters are old school. [Reply]  [No Email]
David G 10-31-2012 19:35:54 205.215.206.18 Report to Moderator	Re: Phase converters in reply to Mtjohn, 10-31-2012 19:33:47   VFD [Reply]  [No Email]
Mtjohn 11-01-2012 10:51:40 70.198.11.213 Report to Moderator	Re: Phase converters in reply to David G, 10-31-2012 19:35:54   Phasematic site says static converters you lose approx. 1/3hp. Where do I look for any specs on vfds. They look great but need to know more before I will buy. Rotarys look bulletproof and I get the full hp of the motor which is something I want so please share sites or such to look more in depth at vfds. as stated above would like to drive multiple motors so would need to be cost effective vs. rotary. Being out in the sticks I like bulletproof. Please expand on vfds and I will definitely look at it. The efficiency is probably not that important as I do not run these all day everyday. Farm repair shop with a streak of inventor. [Reply]  [No Email]