PDA

View Full Version : Static phase converter for 2 speed motor ??



metalmole
12-05-2012, 11:02 AM
I have an Enco mill with a 3 hp 2 speed motor, question is will a static phase converter work on the 2 speed motor ?? I understand it will have to be sized for the 3hp, but didnt know if the 2 speed motor will throw a kink in it....

BigJohnT
12-05-2012, 11:38 AM
I have an Enco mill with a 1 1/2hp 2 speed (or 2hp I forget) motor and high speed would not run on a RPC of the same size. I finally built a 5hp RPC and high speed would work on that. I finally replaced the RPC with an Automation Direct GS2 VFD. I have serious doubts that a static phase converter will run that motor on high.

John

SGW
12-05-2012, 11:55 AM
Yes, it should work, as much as a static phase converter can be said to work on anything. I ran a 2-speed motor with a static converter for a few years until I wised up and bought a VFD. With the price of VFDs these days, I strongly encourage you to forget the static converter and get a VFD. The performance will be much more satisfactory. Unless you can set up a static converter extremely cheaply, or for free, I wouldn't waste the time fooling around with one.

EVguru
12-05-2012, 12:00 PM
A phase converter correctly sized to run a 3hp motor will work just fine. That's how my Bridgeport clone was set up and ran without any problems.

On the other hand, the static converter made the clutch on my Harrison lathe rattle worse that a Ducati's, so I converted to a VFD. The twin speed motor on the mill couldn't be rewired for 240v operation (already wired Delta on high speed), so Sir John supplied me with a replacement single speed motor and an adaptor plate. I've just done the same thing for the same reason on a Denford Easimill.

Peter N
12-05-2012, 12:01 PM
I have a 3Kw/4HP static converter and it very happily runs the 2-speed/2HP motors on my Bridgeport & Colchester flat out (4500RPM on the Bridgy), and the 2HP/1-speed motor on my J&S 540 grinder.
My unit (from Transwave in the UK) has a switch setting which allows you to vary the boost level by switching in different capacitors. For most operations which use the low-speed motor setting I use the switch on position 3 (out of 8) and for all the high-speed operation I've never had to go higher than 5.
Worked very well for me for the last 5-6 years and completely trouble free.

lakeside53
12-05-2012, 12:51 PM
It will work but remember that your 3hp now has to be derated to 1.5hp or so... or you will exceed the motor current allowed. If you don't have a current overload contactor, consider fitting one, and adjusting it down.

Static converters used without great care are a poor choice, and even if the manf says they will allow delivery of 66% of the original 3 phase power, they are either dreaming, uninformed or lying; in addition to the phase loss you have to consider the effects of voltage inbalance.

A vfd connected to the high speed winding configuration only (assuming the power varies widely bewteen the low and high ratings) is your best choice.

metalmole
12-05-2012, 01:00 PM
It will work but remember that your 3hp now has to be derated to 1.5hp or so... or you will exceed the current allowed. If you don't have a current overload contactor, consider fitting one, and adjusting it down.

Static converters used without great care are a poor choice, and even if the manf says they will allow delivery of 66% of the original 3 phase power, they are either dreaming, uninformed or lying; in addition to the phase loss you have to consider the effects of voltage inbalance.

A vfd connected to the high speed winding configuration only (assuming the power varies widely bewteen the low and high ratings) is your best choice.

So I could wire up the VFD on the machine pigtail and set the drum switch to high ?? And would I need a 3 HP VFD or would it need to be uprated.....

Larry Swearingen
12-05-2012, 01:47 PM
Why not just call the company directly and ask them the question ?
After all they are going to know more about their product than these guys.
http://phase-a-matic.com/StaticDescription.htm
I went with a Heavy Duty model to run a 2 Speed Motor on my Burgmaster 1D Turret Drill
because I wanted to utilize the Automatic Speed switching capacity on the stations.
If you aren't familiar with the Burtgmaster it sets different speeds on each turret station
and it can be switched between high and low speed.
It works as advertised for this application. I use vfd's on my Mill and Lathe.

Larry S
Fort Wayne, IN

lakeside53
12-05-2012, 04:24 PM
So I could wire up the VFD on the machine pigtail and set the drum switch to high ?? And would I need a 3 HP VFD or would it need to be uprated.....

You can but you should get rid of the drum switch and wire the vfd to the motor directly. If you want the drum-switch-like configuration (I prefer separate start, stop and fwd/rev), wire that to the VFD low voltage inputs. You only need a 3hp vfd if it's from a reputable brand.. Don't buy the super cheap "no-name" Chinese junk. If you want quality, buy a Hitachi WJ200-022SF ($339). Plenty of guys here can help you program it it.

How about updating your profile so we know if you are in South Africa or New Jersey? Some may not think there is much difference but when it comes to electrical it matters!

EVguru
12-06-2012, 04:56 AM
Don't buy the super cheap "no-name" Chinese junk.

My Chinese inverters are all badged Huanyang, so that must be why they're all working just fine.

I'm just changing out a Siemens VFD for a Huanyang. The old Simoverts (I've got two of them) have always been a bit troublesome.

I'll probably do the Eurothem next. I've got it running my bandsaw, but the low end boost isn't set up right and the Huanyang manual is better than the Eurothem one!

lakeside53
12-06-2012, 12:35 PM
Sometimes you get lucky no matter what rating they give it or name they slap on it. ;) Last year a vendor submitted the Huangyang as part of a bid. It got scratched immediately when it wasn't clear if the UL sticker was an actual registration or a copy; the vendor couldn't supply a traceable registration number.

I've installed more vfd than I can remember (which is getting easier as I get older!), and the one that impresses me most in the more affordable range (relatively...) is the Hitachi WJ200-xxx series. It appears they ported the processor and code down from their SJ700 series, then added to it. I suspect the SJ700 will soon be replaced with an WJ700. Hitachi dual rates their inverters for "VA" as well as heavy loads. For example, the 3hp is dual rated to a 4hp (read the docs for conditions). The "no name" Chinese rate their optimistically without definition as to operating conditions. You do get what you pay for, but if it works for you... that's fine. If you want to go the lowest cost route, buy an inverter larger then you think your need. I suspect most home users don't use full hp often; can't try that with many industrial applications, compressors, fans etc.

Alistair Hosie
12-06-2012, 03:49 PM
In my two shops I have 2 vfds one for my milling machine and one for my selection of wood lathes used one at a time of course.I also have a 3 phase static which I converted to rotary with use of a motor first in line not running anything I have used this both static and with it's conversion to rotary really problem free and also was forced to buy an expensive rotary convertor when neither the vfd or the static did for my machine lathe as it has variable speed all that would work is a rotary nothing else would do.When I found this useful I converted my staTIC IN THE WOOD SHOP AS A ROTARY AS SAID.tHE VFD ARE GREAT BUT WON'T WORK ON ALL MACHIONES AND THE rotaies are better but don't do speed control which I need on my wood lathes as said I have two quite seperate buildings and therefore have two seperate set ups.So it is not true that vfd's are the end all as they won't work my metal lathe and the statics don't work with braked machines as I had to disconnect the brake from my saw. Alistair

michigan doug
12-07-2012, 11:58 AM
A rotary phase converter is always better than a straight up static converter. I have one that services my 2 hp bridgeport very nicely. They are not overly complicated and I could service it myself if I had to. I have rural flaky electricity, so I am a bit leery of a vfd. If the vfd coughs up a hairball, there's nothing I can do to fix it.

But, my rfc can't do magic tricks like run 1.5x overspeed, or extra slow speeds without changing belts (if you have belts...).

It's nice that we have options, but the static would be my last choice.

finest regards,

doug

lakeside53
12-07-2012, 12:51 PM
Here's another very good reason why a static converter sucks - and not just because YOU have to limit power to about 50% of the original motor spec...

An RPC is just a static converter connected to a motor. Notice how the rpc motor vibrates (in comparison to running it three phase), and that the general recommendation is to mount it on rubber feet to help this? When you connect a static converter to your machine, it's basically turning it into an rpc, but because of the rigid motor mounting, all that vibration is transmitted though the motor bearings (which does shorten life). You can see this vibration it in many surface finishes, particularly on the likes of a surface grinder.