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Hello I'm Back with a Question #2775 11/28/2021 03:09 PM
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Old as Dirt Offline OP
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I read the posts every day. I've done so little over the last few months I'm ashamed to enumerate them.

In my half assed attempt to clean up my garage I was looking at my Dvorack (Scotsman) Iron Worker. I bought the unit used when I first moved to Houston. It is 3P and I constructed a1P to 3P converter that is located in the hydraulic compartment on the bottom. The electronics are about 20 years old, constructed at the time out of used, surplus, salvaged components. I don't want to replace the motor as it is large a 5HP with the pump attached to the end.

I would like to replace my converter with an electronic version like the DPS units Amazon sells. I believe these are just inverters (no variable freq). Has anyone used these with success? Wave shape problems?

I suspect that building a discrete component unit today would cost more than a inverter unit, plus it would allow me install breaker, switch, inverter into a single NEMA box at the end of the unit in the clean environment.

Anyone used one of these units and have any comments on them. They are of course form the Covid capital. COMMENTS QUESTIONS

Thanks
JLG


James Geraci
Re: Hello I'm Back with a Question [Re: Old as Dirt] #2776 11/28/2021 04:07 PM
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bunkclimber Offline
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I have to say that at $285 for a 10hp version, it is an attractive option pricewise..I'm not seeing any ventilation slots so Im guessing that it isnt an electronic type inverter,which would require a heatsink and cooling fan for the mosfet/IGBT power transistors..I'm thinking this is a capacitor static converter in a compact enclosure. The actual VFD drives from China aren't that much more money and are reliable as ever these days..I used to buy only Toshiba VFD drives and the eBay China-made ones are almost as good. You can program the VFDs to go 100% full-output depending on how you strap the control terminals and programming..The cap static converters don't allow the motors to develop full rated horsepower like a VFD drive or rotary converter will..so for a single motor one of these DPS things might be OK depending on HP % of load on the motor. They do look pretty compact for building into a tight spot like your ironworker. For my money I'd go VFD.

Re: Hello I'm Back with a Question [Re: Old as Dirt] #2777 11/28/2021 04:50 PM
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sonny Online Content
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I was told that these things eat up the motor windings. ---- I did use one for a short time on our die press before we got the 3-ph hooked up.
Right now I am still trying to figure out how to go on my big old, (actually ancient), SB lathe. Cant put different motor on it very easy since the drive system is a chain like a timing chain in a car, so this makes for a problem.
The motor on this one is only 1-hp and I still have the 2 static boxes . one is from the shaper 5-hp and the die press one I think is 7. It ran the 5 hp hydraulic pump and a 2 hp ran the cross travel.

For limited use, I am thinking they should run for a while.
Still looking for options too!


"A machine you build yourself is a vote for a different way of life. There are things you have to earn with your hands."
Re: Hello I'm Back with a Question [Re: Old as Dirt] #2778 11/29/2021 11:08 AM
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Bunk: I guess I am getting too old for this crap. The thermal aspect of the DPS unit never entered my mind. I will have to get more information on the DPS units as I seized on the low price and the fact I do not need to vary the freq just change 1P to 3P and get close to 5HP out, and the attractiveness of the small size.
Do you have a VFD manuf you would suggest.

I have to admit I am at eyeball level underwater on VFDs. I understand in general terms how they work, but have no useful application experience.


Sonny: For an old motor that would be a PITA to change out I'd stick with a static converter. I would suspect most newer motor would work with inverters with no problem. Film coatings for magnet wire have improved significantly in recent years. Older equipment was not made for crappy sine waves with strange garbage floating around on the supply voltage.

Thanks for your comments.
JLG


James Geraci
Re: Hello I'm Back with a Question [Re: Old as Dirt] #2779 11/29/2021 11:56 AM
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bunkclimber Offline
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JLG,
the brand I used last was a Huanyang 5hp VFD for a gear drive drill press..it's been going strong for about 4yrs now, I had to get programming help from the manufacturer,they have an interpreter that will return your email if you need it,they were of much help in getting it going..You have to enter in motor information and what terminals you want it to read for off/on and speeds,its not too hard if you read the manual that comes with it. Most of them work with a common pin that you short to one of three other pins with a switch or switches to select speeds or use the keypad. They all pretty much work the same,just some quirky differences but for the most part they are pretty easy to use. I have used the older Magnetek and the newer very compact Hitachi VFDs and they are top of the line for my customer machine jobs. Once you work with one of these you won't be using anything else. All you need is a 2000ohm variable resistor to change speeds,or just use the internal keypad to stop/start it right from the keypad.You can also wire it to turn on/off with a simple toggle switch,or separate lightswitch if you want. For a 5hp on eBay they are at $198 with free shipping. One thing I would recommend is to unplug it when not using it to limit spikes and surges from taking out the computer in them..I unplug mine whenever Im done with it..limits exposure to the powerline surges..FWIW best of luck

Re: Hello I'm Back with a Question [Re: Old as Dirt] #2781 11/29/2021 09:03 PM
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Bunk: Thanks for the information. I was hoping that I would get a response from someone like yourself that has real world experience and advice.

I did spend some time perusing posts on the DPS unit. Watched DPS manuf's hook up video. Consensus was innards are static except one comment was unit might have a a voltage sensor and a solid state relay to single phase the motor when it reached speed.

I need to remove the panels and double check the voltage & amp rating on the motor before I order a VFD. I should have known the DPS unit was too good to be true!
Appreciate your help
JLG


James Geraci
Re: Hello I'm Back with a Question [Re: Old as Dirt] #2785 12/01/2021 06:37 AM
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bunkclimber Offline
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JLG,
I'd argue the statement 'they are too good to be true'-they just have limited applications in which the motor and DPS would pair good..they only give about 2/3horsepower and a good bit of heating of the motor under load as well. They might be good for a light use motor like a pedestal/bench grinder, small drill press or something like that- something that has limited use cycles..if it's a VFD chances are it has a cooling fan, or is less than 1hp in capacity. Some of the old Magnetek drives were without a fan,the ones I worked with were 1hp 460v,not much current there.

The DPS looks to me like it should be enclosed in a motor control cabinet,exposed terminals lead me to believe it's not designed to be externally mounted..not sure if it's finger safe either.

Re: Hello I'm Back with a Question [Re: Old as Dirt] #2786 12/01/2021 11:45 AM
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Bunk:

Well, my comment was in the context that it's essentially a duplicate of the unit already screwed to the machine. I was hoping it would replace my hand built unit in a fell swoop with a nice neat little box, give me full power and allow the controls to be housed in a single cabinet.

Actually, if I had a DPS 20 yrs ago I would have snatched it up as I remember spending an inordinate amount of time getting the converter I built sorted.

The problem is I assumed functions the unit had without knowing what the hell the unit actually did have. A failing that has bit me in the ass in times past.

You are correct and I appreciate you taking the time to comment.

JLG


James Geraci

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