Vfd vs dps vs new motor help

[hamsaw5000]

Hi, im the new owner of a Startrite 503 bandsaw. I currently only have single phase power in my workshop and my new bandsaw is 3 phase. Im looking for guidance on which option would be suitable for me to get my bandsaw up and running. Any help will be greatly appreciated .

The Startrite 503s motor doesnt have a data plate anywhere on it but the bandaw does have some of the kw and rpm details on a sticker that states 400v, 50hz, 3.5kw input (3kw output), 1400rpm, and full load current 7a (see attached photo).

I was looking at getting a vfd as this seemed the most affordable and fairly simple option with the added benifit of varying the speed. Ive been a bit unsure of what drive would be suited for the bandsaw as i cant find any that match the specs of the motor. What i did find was this vfd but unsure if it was suitable.
https://www.ebay.co.uk/itm/114869886069
A dps or digital phase convertor was the second option as it would be quite straight forward with a little bit higher cost. Added benifit of future 3 phase machines without dedicated vfd's.
https://www.jfkelectricalni.com/product/digital-phase-converter-4kw-5-5hp-240v-in-400v-out/
Final option would be to get a single phase motor but i would rather keep the existing motor that came with the bandsaw.

Im just very unsure with there being some many things that i could slip up on when purchasing equipment. Im no electrician so i dont know if the vfd or dps ive included links to would be suitable. Its just there are so many of these drives and convertors have different figures im clueless as to one that would be suitable and not cause issues or damage the bandsaw motor.

I would really appreciate any help offered.

Sam

 

[Spectric]

The best option is the phase convertor, no modifications on the machine, you can have multiple three phase sockets and then buy the more solid three phase machinery at often better prices. The phase convertor can also provide a higher power output only governed by your single phase supply when compared to the invertor and changing a good three phase bandsaw to a single phase machine is really last resort.

 

[Fitzroy]

I’ve put VFDs on a few machines following threads/advice on various forums. Nearly all the experience I’ve run across has been stuff you could run from a 13A socket, ie sub 3kw. A consumer grade VFD at 4kw seems like a stretch and with little user experience that I’ve come across.

If you do go that way you’d need to move the motor from star to delta, as per the diagram in your last photo. You then have to require the motor directly to the VFD, and run/stop it from the VFD. If you want to use the original start/stop, and the interlocks on the case this is all more tricky stuff. Also I think the 503 came with a dc injecting brake, which is another thing I’d be unsure how to incorporate with the VFD.

In my opinion on such a large and high quality machine I’d go the DPC route. It feels much easier, more likely to succeed, and less intrusive/chance to break your new pride and joy.

FitZ

 

[Sachakins]

+1 DPC

 

[Sideways]

Either which way, at full load that bandsaw will be drawing nearly 20A from a single phase 240V supply and that's assuming the vfd or phase converter is 100% efficient.
Read the specs carefully about the largest single motor a DPC will start, not just it's headline rating, and you'll probably be looking at something 5kW or greater for full capacity and max versatility.

 

[Ttrees]

Your choice may depend on how many other machines you've got/or have planned,
but I take from your comments from your final option of getting a single phase replacement motor
that you might be happy enough to get this running.
I'm also under the assumption, that you've got the juice i.e 16a sockets installed for such an option.
If using on a 3 pin plug, with rated fuse to handle say double the motor draw
then it would need de-rating for sure, as I believe 3 hp is the max for that.
That's really pushing things as far as I'm concerned,
and with no extraction or anything else either.

I see you've clearly demonstrated that the motor is indeed dual voltage,
so there's options.

Personally I'd go VFD, as I had the significantly lesser version on paper and indeed real life,
of that machine, and it had a 1.5kW motor, which I ne'r got to test properly,
but it started with some rigor.

I like the soft starting from the VFD on my 24" saw now, which along with taming that startup,
could be utilized to perform braking functions...
should you want that, or if the in-built breaking capability might be good enough.
Your preference might well depend on the table size, or if you've got employees
then you might need something which can allow for "dynamic braking"
of which some components are missing from many units, like the Huanyang.

Other features might be de-rating the motor hp, to say an ample 3hp,
and back again if need be.
If you're planning on getting something rated higher than needed, then that de-rating feature is needed.
i.e the "parameters" to type in the motor kW, and amperage rating, in order to do so,
don't see it on the booklet of some downloadable manual, then guess not.

Auto shutoff cooling fan for a one bandsaw workshop is a must for the irritable or well heeled,
and the better ones, some like Invertek, but there are a few UK companies I believe,
might have better tech for keeping the motor cool if the machine gets bogged down for some reason.

I can attest to this, having damaged my original Huanyang and nearly my motor,
by bogging the saw down, though that wasn't the fault of the unit whatsoever.

Might want to make sure there might not be a motor break of some sort on that machine,
best to mention for the knowledgeable folks here.

Can't think of much else, suppose could mention IP ratings for dust,
or if you wish to make up yer own box for a cheapie.


Hope that helps
Good luck with the new machine.
All the best

Tom

 

[Spectric]

which is another thing I’d be unsure how to incorporate with the VFD.

You cannot because the VFD can only have a single load connected, the brake would be another load.

 

[Inspector]

Some VFDs can have external resisters added (bigger on heat sinks) for braking demands greater than the VFD is made for.

Pete

 

[LancsRick]

I'd vote for DPC if you're contemplating future machines. The 3ph are nearly always cheaper due to the issues with people having supply in the second hand market. VFD you're just making a one-off cost for one machine. To me that's the worst of both worlds - faff of setting it up plus additional cost per machine.

 

[Ttrees]

Some VFDs can have external resisters added (bigger on heat sinks) for braking demands greater than the VFD is made for.

Pete

Which brings up another very important point if going that way,
seeing as technology is advancing by the day!

Forget those old "resistors" they're are a thing of the past, and in fact nearly useless for those
who've not got any insulation in their shed.
In reality, considering this day and age, there really is oodles of choices....
even for the health conscious!
Fair enough, it might take one out of their comfort zone, but without taking the leap,
the question will remain in the back of ones mind...
why deny oneself of such an opportunity, I mean it just makes sense.
What's there to do anyways?..well, virtually nothing, and the possibility's are endless.

So with that said, I strongly encourage one to consider all aspects of the matter of dynamic braking, and what that could mean to your LIFE,
and never mind the naysayers, they're just jealous of what's on offer nowadays.
and I can bet you a sausage roll on that!

Should one wish to really kit out their bandsaw, or infact any machine in their "shop"
then look no further,
Here you go, and no need to thank me, you can do that when you get around to it,
as I'd prefer to get tips from those, shall we say.. more accustomed to the refinements
and idiosyncrasy's of these new fangled compact all in one units.

Think of the time and money saved, and I'm probably leaving out a whole bunch of stuff at that.
Oops, ranting again, I keep forgetting to get that link for ye...
Here ya are
http://sauerandsteiner.blogspot.com/2012/01/magnificent-with-apologies-to-jill.html
Suppose.. like all the links I post on the forums, it'll never be seen.
I think I've got those pictures saved, so I can plonk them here.
With that said, you'll have to understand that was some time ago,
and certainly wouldn't be the off the shelf choice, like what we can have today!


Exhibit a, what's a fine example of a Yeats bandsaw, understandably more than enough cast iron for the job.

Now lets consider the resistor of choice

Why would anyone want such a thing is beyond me, but perhaps there's reasoning for it, who knows...
I mean, all that trouble of hooking it up, there's gotta be a reason for that choice?

All I can say is, it's sure got me scratching my head.

Perhaps you might say, it's a lot of "hot air", but the next VFD I'm going gettin,
It's gotta have the tech, so I can stick one of these bad boys on top.
At the end of the day, It's clearly the sensible option,
Especially if you've done yer homework, and being reasonable,
You'd practically be mad not to.

Especially as so many, actually have a chest freezer in their workzone.

Now, the question I pose to the knowledgeable, about all this is...
What level of grease protection does IP44 provide?

I've been looking everywhere, and I can't seem to get an answer.
Thanks

Tom

 

[Sideways]

That's brilliant @Ttrees
All you need is a suitably high dissipation resistive element of the right specs.
I wouldn't choose the same solution myself. It needs to be robust enough to run for years, tolerate dust and damp etc and hairdryers overheat and burn out when the cooling motor fails, but it does prove the concept.
Next challenge : find another off the wall answer that is totally passive. No eventually unreliable cooling fan

 

[Ttrees]

All you need is a suitably high dissipation resistive element of the right specs.

I had a quick look, and it seems that you may be onto something.
Seems I may need think again!
Perhaps the solution might be a fail safe backup system, like one of these?

I wouldn't choose the same solution myself. It needs to be robust enough to run for years, tolerate dust and damp etc and hairdryers overheat and burn out when the cooling motor fails, but it does prove the concept.

Some of these new clever devices even come with a guarantee, so provided you don't break the casing whilst doctoring it slightly, then I can see no sensible argument really.

And a little saw dust never hurt anybody, infact doing a quick googleing, it turns out that some wood fibers are actually used as what's called "bulking agents",
so I suppose as long as you clean the blade prior to cutting your very own home baked sliced pan,
then I'm sure you'd be grand...

Next challenge : find another off the wall answer that is totally passive. No eventually unreliable cooling fan

Must look this up a bit more really, and not just for my own shed.
Not hard to see some folks in the business might have reasoning to take things a step further, having multiple employees and such,
I'd imagine they'd be queuing up to use such a machine!