vfd or rotary converter

[royce]

I have one 2hp drill press, one 2hp mortiser and one 5hp bandsaw, all 3 ph.
200 amp single phase service.
I only need to run one machine at a time.
Does anyone have any thoughts on what to feed power to these machines with?
Thanks
Royce

 

[paramud]

VFD will allow you to control speed without changing belts. I am not sure how to deal with multiple machines. I only have one mill that needs 3 phase.

 

[Jlarson]

Unless you want to put a drive on each tool go phase convertor.

Different individual machine tools isn't really an application for a multi-motor drive install.

 

[bloomingtonmike]

You do not put switches after the VFD so the motors would get direct attached to the VFD. I have seen installs do it but it is NOT recommended. All your start/stop/direction/speed etc buttons on a VFD get wired to contacts on the VFD not to the motor in the machine. A decent 5hp VFD is not cheap either.

 

[404]

As

bloomingtonmike

says, no switches after VFD. Very specific about that in the manual.

5 HP VFD are more money than the 3, big jump.

 

[A_Pmech]

A rotary converter will be less expensive and more user-friendly for a multiple machine installation.

 

[Showkey]

I have VFD and move it to each machine. I do shut it down and never switch machines powered up.
1 HP motors on a wood lathe, drill press and small metal lathe.

Mine a 2 HP unit and have less than $140 all in.

 

[royce]

A few more questions if you all don't mind,
What size motor for a rotary converter driving a 5hp bandsaw?
My drill press has a drum switch for forward and reverse as well as one for high and low speed, with that said, would it still be poor practice to leave those switches inline but locked out?
Would it be acceptable to drive a 2hp motor with a 5hp vfd?
With a vfd is there overload protection built in?
Thanks for all the help
Royce

 

[Showkey]

I use only the VFD to control the all the motor speed and direction function.....the stock switches are completely removed.

Generally speaking 2 hp on 5 hp VFD should be ok.

Protection depends on each VFD the operation and install docs should confirm.

 

[Norcal]

Single phase input VFD's are fairly inexpensive for motors 3 HP & smaller, after that it REAL expensive because 3 phase input models have to be used with a 50 % derate of the drive, for example 5 HP motor, then a 10 HP drive has to be used, to make matters worse is that 430.122(A) requires that the circuit conductors be sized at 125% of the rated input. Single phase models do not need to be derated.

A RPC for multi-motor shops is the best choice because existing controls can be retained, VS multiple VFD's or a jury rigged system using one drive on more then one machine.

 

[404]

A few more questions if you all don't mind,
What size motor for a rotary converter driving a 5hp bandsaw?
My drill press has a drum switch for forward and reverse as well as one for high and low speed, with that said, would it still be poor practice to leave those switches inline but locked out?
Would it be acceptable to drive a 2hp motor with a 5hp vfd?
With a vfd is there overload protection built in?
Thanks for all the help
Royce

High and low speed means a motor that can be configured for different number of poles. Useful.

As long as the out put of the VFD is never switched with input power applied then that seems okay. IF it blows up please don't blame me.

 

[Falcon67]

It's mostly money I think at 5HP - about $600 for a single in, 3 out.

http://www.driveswarehouse.com/p-2123-pc1-50.aspx

 

[Mr. T]

I really like the simplicity and flexibility that a VFD offers. If you've got the money to burn it's a nice way to go. If not there's nothing wrong with using a rotary phase converter. Or perhaps just get a VFD for the Drill Press for some obvious advantages.

 

[930dreamer]

A 10hp rotary phase converter would work great, this is what I use for a 5hp compressor, two grinders, one buffer. Use a pony start to reduce the inrush amps and all is well.

 

[royce]

Thanks and a few more questions,
Is it cost effective, power consumption wise to drive a 2hp motor with a 10hp converter?
Does anybody have any thoughts on the rotary converter kits on ebay?
If I go with a vfd for the drill press, can anyone suggest a brand and model number?
Royce

 

[ddawg16]

You could have a 100HP converter or VFD and the energy usage will not be any more if you drive a 1hp motor with it.

I personally would go with the VFD. A lot more flexibility.

Yes, some of the manufactures say to not switch....but it's done all the time. I have one system where a spare 250 HP VFD is set up to run any one of 7 motors ranging in power of 75HP up to 250HP. If you use a computer, you can reprogram the VFD in seconds

 

[930dreamer]

You can make a very simple, no cap start rpc yourself.

 

[royce]

You can make a very simple, no cap start rpc yourself.

Do you happen to know where I might find instructions geared for a knucklehead like me?
Thanks
Royce

 

[930dreamer]

Do you happen to know where I might find instructions geared for a knucklehead like me?
Thanks
Royce

If you go on the Practical Machinist forum, there's a thread for converters and vfd's.

 

[bczygan]

Rpc.......

 

[zkling]

A rotary converter will be less expensive and more user-friendly for a multiple machine installation.

In the long run it will be cheaper and easier once you get everything installed. VFD's are nice as they are plug and play at the machine into a single phase outlet, but add up quickly. If you are in it for the long haul, and it sounds like you are, especially with larger than ~1.5hp motors, you will be better off with a rotary converter.