Bridgeport twin speed motor phase converter or vfd?

Hello,

I've recently got a Bridgeport milling machine and have been using it fine via a Transwave static phase converter for about 1 month. This week it has started tripping out on the switches inside the Bridgeport cabinet. Maybe it's since switching speeds with the switch on the machine.

I guess the motor is not happy with the power supplied by the static converter so I'm just trying to weigh up other options.

What setups are people using with the twin speed motor machine?

Am I right thinking I'd need to replace this motor for a vfd to work successfully?

Thanks,

Chris

As far as I know from my research you can't use the older 2 speed motor as is with a VFD unless you get the full 415v ones, to use a VFD I think you need a twin voltage motor and you run it at the 230v setting in star?
It's been a while since I did synchronous machines at collage so I can't remember the reasons.

Steve

JS knows chapter and verse on these things, I'm sure he'll be along in a bit.

Neil

I always like the broad range of opinions to help weigh up the options and I can't afford to make any mistakes on this as I cant see any spare Bridgeport motors on Ebay if I melt this one :-/

I'm confused, I though induction machines were asynchronous?

Andrew

Chris

By 2-speed I guess you are referring to the 'pancake' motor which is so called because it is wide and not very tall. They run at 2700/1420 RPM and need 380/440V. According to what I have read and been told, they cannot be run from a VFD as they are and neither can they be re-wired internally to let them run from 3 phase 240v. They are also energy inefficient apparently.

I have one also, and a static Transwave 2.2kW. It will only drive the higher speed if I switch over the motor while it is still running at the lower speed. But, I find I have no need for the higher motor speed in all the cutting I do.

Perhaps your solution is the same as the one I toy with. I would like to fit a metric, flange mounted motor with a nominal 1400 RPM running from a VFD. What is needed is a thick steel adapter plate to mount the motor flange and replicate the pancake motor flange to bolt down on the Bridgeport.

Perhaps JS has been here before and could supply an adapter plate? Otherwise I might get round to measuring it and getting one laser cut. The motor pulleys will need modifying for the metric spindle, and you need a separate supply for the table feed and coolant.

Norm.

 

Chris... I've got a spare genuine Bridgeport motor but you'll have to wait until my Daughter inherent's my goods and chattels. The Bridgeport can go with it!

I use an inverter VFD with it and the power feed on the table is run from 110v AC (but not centre tapped to earth).

John

P.S. Why do I keep getting †every time I hit the return key on my iPad?

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Edited By Johnboy25 on 27/05/2015 21:27:43

Hi Norm,

Sounds like you have the exact same set up as me. It seemed to be working ok but has been tripping out and requires me to press the reset button inside the electric box on the machine. What number do you set the switch to on the transwave box? I find I have to tweak it until the motor runs smooth. Maybe I need to experiment a bit more and live with the quirks. Does your coolant pump run while on the Transwave?

Chris

Hi John,

Which type of Bridgeport motor do you run with a vfd? is is a 220 to 220 vfd?

Chris

Chris

With the 2.2kW Transwave I run it at No.4 for Bridgeport slow speed, and it needs maximum No.8 to hold the high speed. Boost will kick in when you first start, but you are supposed to select the lowest number that will sustain drive without boost when a moderate cut is applied. Apparently there are trim resistors inside the Transwave that sometimes need adjusting. The 2.2kW model is only just big enough for the pancake motor. I think it is not recommended to run the coolant pump or the table drive unless the motor is running first, because the Transwave will not supply a proper waveform at lower current loads. The purpose of that switch is to optimise the internals to match the load.

Norm.

There are digital 240v to 415v inverters more expensive than 240v single phase to 240v three phase as they have to up the voltage to 415V. There is at least one forum member using one on a dual speed Colchester lathe.

Bob

Norm,

I think those are about the settings that have worked for my machine. Has yours ever tripped out under load and motor appeared hot? its this tripping out and motor heat that got me thinking about if the Transwave is right for the job. I cant afford down time and expensive meltdowns as I'm on a shoestring at the moment

Chris

Hi Bob,

I have found a couple of those 240v to 415v inverters on ebay but the price seems too much of an investment to just buy without a recommendation. I was hoping someone would say I've used such and such for a year on a twin speed 415v motor with no problems.

Chris

First of all there is a common misconception on what is a two speed motor on a Bridgy.

Some people see 240 / 440 on the plate and assume it's two speed.

Secondly and not helped at all by Bridgeport is they used a number of different legend plates.

Some say 1 - 0 - 2

Some say H - 0 - L

Some say l - 0 - ll

Some say F - 0 - R

Regardless these are all single speed motors and only the last one has the right meaning.

The proper two speed motor has 5 positions and from memory, I can't remember what the different legends are. [ I blame the aluminium sausepans we had as a kid ]

Motors with 3 position switches can be run off anything, phase converter, vfd, or rotary.

Motors with the 5 position switch can only be run off phase converters, or anything that can produce a 440v input.

There are some VFD's sold nowdays that can do this but they are just butchered single phase jobbies with bits added and don't come under any CE or regs so be careful.

Chris also doesn't say if it's the varispeed or step speed but I suspect it's the step speed. It's perfectly possible to fit a metric framed motor to one but it needs a mounting plate [ may have one - would need to check ] but it also requires work on the motor. It is possible to bore the pulley to take the larger metric shaft on the new motor but the shaft isn't that long and there is a lot unsupported given you have to subtract the conversion plate which is usually 8mm.

A 2 HP motor is on a 90L frame and a 24mm shaft 50mm long so the most you have inside a 52mm long pulley is 42mm

A 3 HP is on a 100L frame and a 28mm shaft 60mm long so that is 52mm max.

However the pulley doesn't fit right up to the top to get the belts to line up so in my book making the pulley fit the motor isn't good engineering.

I much prefer to modify the motor to take a standard pulley. You also get a chance to uprate the motor to something better than the original but in excess of 3HP is wasted as the Bridgy bends.

Don't look at me, it's been a long time since collage and I had a crap memory then never mind now

Hi John,

Thanks for the info its a 2 speed stepped pulley head. If I went down the motor swap route do you think the cheap £100 inverters are up to the job?

Chris

Chris,

I have used a few and had no problems with them out of the box. Reading different forums the problems seem to occur when using the high speed motors and remote switches but I feel a lot of that is not understanding the not too clear manual.

There are some good video's on you tube on setting these up.

I have a step pulley Bridgeport, tried for some time to get the 2 speed motor to run on a phase converter, it was never satisfactory. I eventually fitted a Clarkes single phase foot mount motor. The short shaft was a problem, If I had used the flange mount, there would only be about an inch of shaft to mount the pulley. I made a mounting plate and recessed the motor into the plate so that the end cap tabs were flush with the plate, the motor is secured to the plate by the 4 long bolts that hold the end caps on. There is still about 10mm of the pulley unsupported but this has not been a problem in 5 years of (hobby) use. The motor I used was 1HP, which has been adequate. Larger single or 3 phase motors could also be fitted.

Dave

Dave - thank you for the idea of mounting using the four end cap bolt holes on a foot frame motor. With a 90L frame size that possibly gains around 15mm of shaft extension compared with a flange mounting. The mounting is probably not 'manufacturer recommended' but should be strong enough into the main body.

JS - thanks for all the shaft extension info. Could you give me an idea how you would modify the motor to have a longer, imperial shaft? If it involves taking it apart, and welding on a new shaft while the rotor is red hod and spinning in a lathe, I think I will leave that to you and your special skills

Norm

Norm, I also fitted an L bracket from the motor foot to the mounting plate, just in case I forgot to release the brake before starting (AHEM).

Dave