Convertor Issues 240V 1 phase to 415V Three Phase

Hi All,

So whilst I am awaiting contact from JBCuttingtools. I thought I would ask for views on my latest update of my underpowered convertor situation.

Having established, and understood by some, that the convertor changes 240V single phase to 415V three phase in plug and play mode and that the convertor (5HP) is underpowered for my lathe Colchester Student 2500 2.2KW + 3HP on start up.

It was suggested to me that I insert a soft starter between the Converter and motor supply.

So I cant see why the convertor would not be able to power the motor as the soft starter would limit the inrush current on start up, and take the strain away from the convertor

Anybody have any constructive thoughts???

I Cant see why it wouldn't be an OK solution!!!

Gary

IIRC you've got an inverter (box of electronics) rather than a static converter (box full of capacitors and a transformer) or a rotary converter (box full of capacitors bolted to the side of an un-loaded electric motor). Can you explore the configuration options in the inverter to see if there is a 'maximum load/motor power option'? If there is, it could make the inverter limit the output power (giving a slow start) rather than just going balls out and tripping itself.

A soft starter would almost certainly do the same job. It's just a few hundred quid that you might not need to spend.

After a bitt more searching:-

If it's the unit I think it is from your description and the drives direct web site. Download the manual from their downloads page and have a look at page 53 '(18)Number of auto restart attempt' and '(20) Stall prevention level during running'. That should stop the drive tripping out when starting the lathe.

The fact that it hasn't let the magic smoke escape, means that you're in with a good chance.

Edited By Mark Rand on 19/10/2018 01:26:38

On my VFD it stated quite clearly that the VFD had to be directly wired to the motor because anything in between the motor and VFD could damage the VFD . I can change the ramp up on my vfd so it works like a soft starter but trying to run a motor that is to big for your unit is asking for trouble . As Mark has mentioned it may be a setting issue soma good study of the manual could be in order .

Edited By XD 351 on 19/10/2018 06:12:25

There is almost certainly a soft start mode available in the inverter that will limit the inrush current if you study the manual.

I agree; the previous thread established that the inverter ought to be capable of running a 3hp motor. If this isn't the case it would be far better to work out why rather than randomly spend money on items in the hope they cover up the problem rather than solve it.

As a starter it would be useful to know what the exact setup looks like, and see photos of the inverter and motor nameplates to check current and voltage ratings.

Andrew

.

Shown in Fig. 44

... but beyond my comprehension

MichaelG.

To be constructive more information about the Converter is needed. It feels as if we're on that part of the map that says 'Here be Dragons'.

It's easier to identify what the dragons might be than to prove they don't exist!

• Unless the nature of an inverters output circuitry is understood, it's not a good idea to mess with the output side. Three problems:
  • the VFD's output devices might be sensitive to anything other than a motor load, especially hot-plugging, or unexpected capacitance & inductance; or
  • the VFD waveform might not suit a downstream device expecting pure AC; and
  • the controller may adapt to a motor by measuring how the motor loads the output, and be upset by something unexpected in circuit.
• There are several different types of soft starter. They work in very different ways, and who knows how compatible they might be with the output of a VFD without reading the manuals and/or asking the maker? Certainly the inductive type of soft starter is very likely to cause trouble on the output of a VFD, though it would probably be fine on the input AC side. Conversely an electronic soft starter might be OK on the output, and not acceptable on the input.

If it's not covered by the Manual, proceed at your own risk.

Before trying a soft starter, I'd want to eliminate other possibilities first. For example what Error Code does the converter throw when it fails? It might show:

• A sag in the mains input voltage caused by the switch on surge. This is a suspect if the workshop happens to be on the end of a long spur. The cure is a fatter cable.
• Overload on the output side. This might be cured by slowing the rate at which the VFD ramps up the frequency. How this is done may not be obvious - searching my cheapo VFD manual for 'soft start' reveals nothing, but in fact the VFD can be configured to achieve it. ( It's under 'Frequency Control' ).
• Most Manuals have a Troubleshooting Section that might suggest answers to particular fault code.

General comment on VFD Manuals. I find they usually have a straightforward 'get you started' section that's probably plenty good enough for most people in most cases. Unfortunately, if you have a deeper requirement like this one, the easy bit is followed by a dense mass of terse engineering jargon written for experts. Very likely that's where the answer is, unless the VFD seller can help.

I'm often in favour of experimenting with this sort of problem to see if a solution works. Given the cost of getting it wrong, I'm nervous of recommending that while there's hope of getting an authoritative answer. That said, putting a Reactor type soft starter on the input AC is unlikely to damage anything - worth a try?

Dave

Edit pesky smileys...

Edited By SillyOldDuffer on 19/10/2018 11:23:21

The converter in question is capable of bing used as an inverter (which would run the motor OK), but in the current set up it is being used out of the box as a fixed voltage converter to allow another machine and the lathe to be used with their original switch gear and accessories.

Neil

Neils summed it up and seems to understand the problem.

2.2kw motor yes, but its powering a geared head in turn a variety of differing weights of chuck.
To explain whilst your ok in a 3ltr Diesel when locked in 5th it will eventually pull away from standing start. Try that in a 1200cc, 3rd might struggle with but not 5th. Add to the criteria the heavier the load ie size of chuck, its takes longer to get up to speed than say just a bare spindle. Same in a car heavier the load the slower it takes to get up to speed.
Now theres a max time limit think its 10 secs where it will give 150% or more overload upon starting, not enough when in top range of speeds it takes bare spindle on mine 8 -9 secs to reach 2500rpm. Add a chuck and it will exceed 10 secs and come up with an error and shut down. Do this often (several stop and restarts even in mid range) over 1hour 23 mins and guarantee that invertor will be as good as scrap.

Forget any soft start it wont do a thing. All you will get is the contactors and relays chattering until it ramps up closer to 400v, therefore once up to voltage its a hard start.

Gary whats it like when you give the spindle a push start whilst hitting the start lever? Mid range low

There is a cheaper option try a decent modern new motor first, mines been gold the last 12 months since doing so even with the 10hp invertor. New motor may have a very different cage and shaft size unless you pay through the roof. I had to make up a new motor plate and bore out the pulley.

The only way that 4kw invertror will power that lathe is like a vfd, straight to the motor direct. I had one it lasted 1hour 23 mins and still waiting for my money from said supplier 7 1/2 years on.
You then in control panel setup the soft start usually 3 seconds.

Hi All,

Many thanks for your replies.

For those few that understand my dilemma many thanks. Jon, again many thanks for your comments however I would stress the following.

Currently the Convertor starts the lathe, in any gear, and with no assistance every time. my only thoughts are that it probably dosent like it due to the high inrush current and that it will be counting down the time to failure.

I cannot see why a soft start won't work hence my question. Unfortunately no one has provided me with a reasonable explanation as to why the soft start won't work. Jon your explanation about the chattering of the contractors is not relevant in my case as I have supplied the control circuitry with an independent supply. Hence the soft start has no effect on the contactor coil voltage that pulls the contractors.

Therefore my question comes down to ......I assume with 415V ramped up slowly to the motor supplied by a soft start device the inrush current should be limited and hence the load on the convertor reduced and its life elongated? and save me £2000 for the price of a new device!

Gary

Not the supply the 400v 3ph output, wheres that go to?
Independant supply of 400v to on/off, contactors, transformer and all?

Jon if you are unwilling to modify your approach and use the soft start mode of the inverter I suggest you just go ahead and invest in this soft start unit that apparently exists and report back on how you get on.

Hi Jon,

Sorry I don't understand what you mean. The soft start would be inserted between the contractors output and the motor.

As for the independent supply to the cofactors and control switchgear, that is via 240V single phase into a transformer on the machine which provides 110v supply to the contractor coils

Gary

Did you look into the

(20) Stall prevention level during running

in the manual?

Dear god, what a carry on. You should just connect the VFD directly to the motor and stop buggering about with this daft talk of soft starters. Why ask for advice and then just ignore it?

Seems you actually paid £2k for a VFD, so please let us know how much you end up paying for a pointless soft starter. 3 or 4 figures?

Murray

From the other thread, you said:

​“unfortunately the drive you link to is only 230v, not 415v and is incapable of running all the control switchgear. Hence the need for a higher cost plug and play device in this instance that coverts single phase 230V to 3 phase 415V and has inbuilt EMC filtering and sine wave filtering to produce a cleaner PWM sine wave capable of operating contractors and relays etc so that the lathe can be controlled from its intended original controls.“

You are now saying the control and contactors are not running from the inverter? A considerably different scenario.

No reason not to allow the inverter to run up the motor as it is designed to, as a VFD? The simple difference is that the inverter will ramp itself up from zero Hz to selected motor speed, so not be making 50Hz at zero amps and suddenly being faced with an almost dead short - well, an overload current, at least - and a motor operating at a different frequency than the inverter output while accelerating from zero rpm to operating speed (think here flux slippage).

You need to make up your mind how to operate your machines. Perhaps separating the control contactors from the motor drive and operating either machine as a VFD, not as a simple voltage converter, would save you the ccost of a larger plug’n’play converter?

HI All,

Well I thank you all for your advise. I will aim to continue to use the device in "Plug and Play Mode" a scenario that many are obviously unfamiliar with, and will install a so called daft soft starter, and will let those who might be interested know how I get on. It just might come in helpful to others in the future.

Sorry to those that think I must use the functions of the VFD, its just not an option that I wish to pursue

I will make it clear whilst I have asked for opinions and advise, unfortunately the advise given by some is pointless as they hacve mis understood the question being asked, sorry but fact.

However I will say as always its interesting to sift through some of peoples thoughts, opinions and advise as on occasion a real jem appears.

Again thank-you. Now where do I find the so called daft soft starter?

Gary

.

Gary,

As per my first post on the previous thread ... RS Components would be a good place to start.

**LINK**

https://uk.rs-online.com/web/c/automation-control-gear/electric-motors-motor-controllers-peripherals/soft-starts/

I tried a basic filter on 'Voltage Rating' to give a reasonable shortlist, but will leave you to explore.

[ sorry, I couldn't find 'daft' as a filter option ]

Yes ... Please do let us know how you get on.

MichaelG.

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Edit: The post by Clive Foster, on this thread from 2015, looks encouraging:

https://www.model-engineer.co.uk/forums/postings.asp?th=111651&p=2

Edited By Michael Gilligan on 19/10/2018 23:38:52