Bridgeport and transwave

Hi all,

I'm a bit new to this, I ve just acquired a transwave static converter for my bridgeport j2b as it was going for the right price. The bridgeport seems to have 5 core SWA where as the transwave receives 4 core. How should this be connected. I will probably get a sparky in however I'm curious. Hope this makes sense.

Matt

Most industrial machines are 3 phase + Earth, some also have a neutral connection which is only required if something on the machine is 240 v. That item will use one of the three phases and neutral to give 240 v

Hard to describe, so hope it makes sense.

.

As Alan says.

3 will be used for the 3 phase (this will be the main load)
1 probably used as a neutral for sundries and perhaps the control circuits.
1 probably used as an additional earth to the SWA sheath.

Nick

I do not wish to dampen things but I have already been down that route. A transwave static inverter on my Bridgeport varispeed would only run the machine for 7 or 8 minutes then I would have to press one of the resets in the machine cabinet. The transwave static inverter runs my 3 HP lathe ( over 4 years now ) very well. I had Transwave people out to sort the problem and check the wiring but no improvement. The Bridgeport now runs fine off a cheap £90 Chinese VFD. The VFD was wired for me by a friend who knows about electronics and he could not find a reason for the static inverter not working so it could have been a problem with my machine, I will never know the real fault.

Bridgeport motors don't seem to do very well on static converters. I know of one that burnt out when used in Delta connection, i.e 240 volt, mode. Had mine on a 440 MotorRun static converter with step-up transformer. Worked reasonably well but I never had the nice warm "it's good" feeling. Adding a 5HP pilot motor to make it a "sort of" rotary converter improved the running considerably but it was never as good as a proper 3 phase input. VFD driven now, whole shop one from Drives Direct in my case, and its happy as Larry.

There are considerable electrical, magnetic and mechanical (inertial) shenanigans involved in making static and rotary converters work. The design details of the motors involved have considerable influence over what is going on. I suspect that the Bridgeport motor design is inherently unsuitable. Probably something along the lines as to why two speed and high efficiency "energy star" motors tend not to do well.

Not sure if anyone really understands this in detail. However there has been a considerable revival of analytical engineering interest in the Steinmetz connection, the underlying design of converters, of recent years to support application of induction generators in wind and other renewable energy applications. Common designs for relatively inexpensive three phase induction generators are essentially the same as a 3 phase motor. The big question in generator applications is how to maintain output balance when supplying unequal single phase loads. Which is the same, albeit reversed, problem as balancing a 3 phase motor on a single phase converter. The maths is the same either way. The sums are monster complicated too when you start getting serious.

Clive.

Edited By Clive Foster on 30/03/2017 11:51:16

Edited By Clive Foster on 30/03/2017 11:52:08

I run my Bridgeport with a very early Transwave converter, and have had no problems running it all day. I have run it for about 8 years like this.

I have had the contactors in the panel trip out when it is very cold, when the spindle has a job to turn as the oil is so thick, but once it has warmed up it is OK. I had the original DC table feed motor fail gradually a year or so ago, it would not run slowly, just at full speed, and then gave up the ghost all together.

Chris Gunn