Thoughts on this VFD

[Ubique]

Other than the simple 'string' inverters, which are being phased out now and were never really a thing in UK, they are typically a two stage conversion, DC-DC to ramp up the voltage and then DC-AC which is where the grid synchronisation comes in. it's also the same system used for diesel fuel injectors where a high (~160 - 380VAC) voltage is required to get the fast switching on the Piezo's

ETA - just to muddy things even more, BEV's use bi-directional inverters to control the drive motors and charge the batteries during regen. braking!

 

[Ubique]

I expect most larger string inverters, for PV, will be running with a high DC input, so 3 phase versions will not be too difficult as they will likely only be dropping voltages, not increasing them.

The problem with string inverters is they have to be capable of ramping up voltage - or shutting off their output if partial shading occurs. There is also the interlinks to consider, you can't link too many together. The dealership where my Mrs. works has just had 2/3 of the roof covered with solar panels, I was chatting to one of the installers whilst waiting for her to come out of work and he mentioned a max. input per inverter of 120VDC, now that may be due to design factors, site limitations or just 'how it is' - I couldn't say, the way they were chucking the inverters up the access towers, there wasn't a transformer of any significance in them at all, being a commercial building, they're obviously on three-phase power. It's entirely possible that some of the solar farms do have a much higher input voltage, that's outside of my sphere of knowledge I'm afraid.

 

[GRW]

Haven't read all the comments, but have you considered a nice simple robust Transwave Rotary Phase Converter to run your 3ph Lathe?
We've used them in work and seen plenty in service with rural woodworking and metalworking firms - and they are good kit, and a good firm to deal with.
(Peter was the guy I recall).

 

[daleyd]

Other than the simple 'string' inverters, which are being phased out now and were never really a thing in UK, they are typically a two stage conversion, DC-DC to ramp up the voltage and then DC-AC which is where the grid synchronisation comes in. it's also the same system used for diesel fuel injectors where a high (~160 - 380VAC) voltage is required to get the fast switching on the Piezo's

ETA - just to muddy things even more, BEV's use bi-directional inverters to control the drive motors and charge the batteries during regen. braking!

Yes, a vfd can do the same - when slowing a motor down it can regenerate from the motor, it gets dissipated into the dc bus but you can get braking resistors to dump more energy into during heavy braking if required - this is how they can stop a load quicker than just removing power and freewheeling. Most vfd now are whats called 4 quadrant drives, where they have this capability, in the olden days when they first appeared the cheaper ones were known as 2 quadrant drives, ie they could only accelerate but provided no braking torque.

Having just done a quick Google of solar inverters it seems to me that most will employ a transformer somewhere to do the voltage boosting. In that respect I can't see how they are much different to a vfd which boosts the voltage other than the solar has a fixed range of parameters to work with (in terms of the output stage) whereas a vfd will need to constantly change these and its the input side which will remain constant (ish)...

 

[Fastdruid]

At the power station, neutral is connected to earth (ground). No VFD uses the neutral. It is the phase-to-phase voltage we need to make 415v.

What a VFD does is to take the incoming supply, rectify it to DC and then using a microprocessor to control IGBTs chop it up again into approximations of AC sine waves 120 degrees apart*. For 415v output from 230v input, you'd need a voltage step-up stage (boost) between rectifier and IGBT. You can buy 230v in and 415v out VFDs but they are not common and are expensive - Look at Drives Direct in the UK for info.

* Even 415v 3-phase in and 415v 3-phase out ones work this way, except they use a 3-phase rectifier. Many 230v VFDs are also made for 3-phase input but in UK our power is not supplied in that manner.

Why not just use an appropriate transformer to step the voltage up first? Obviously it would have to be an appropriately sizable transformer but in theory you could step up to ~400v then run an appropriately derated 3p 380-440v VFD (I don't think you can get a single phase 380-440v vfd) to run them at full power/speed.

 

[Lewis_RX8]

Haven't read all the comments, but have you considered a nice simple robust Transwave Rotary Phase Converter to run your 3ph Lathe?
We've used them in work and seen plenty in service with rural woodworking and metalworking firms - and they are good kit, and a good firm to deal with.
(Peter was the guy I recall).

I saw some of those and they do look really quality built to last bits of kit however getting one to suit 7.5hp is getting a but much paying almost the same price as the lathe for the power to run it

Also some second hand ones but they hold there price so still a lot more than the VFD without the frequency ability however they are a good reliable option that would take the least messing about with so eyes are peeled for used ones.

 

[GRW]

I saw some of those and they do look really quality built to last bits of kit however getting one to suit 7.5hp is getting a but much paying almost the same price as the lathe for the power to run it

Also some second hand ones but they hold there price so still a lot more than the VFD without the frequency ability however they are a good reliable option that would take the least messing about with so eyes are peeled for used ones.

If it helps... their rotary is basically a static with an ac motor connected to give you a more "normal" 3-ph supply with no need to switch settings, and no minimum motor load (which statics do, which can be a pain if you want to run small feeder motors etc before the main kicks in).
In our old workshop we had a Transwave static hooked up to a pilot motor, and it ran even the big heavy old 7.5kw metalworker no bother.
So... if you have a big ole 3ph motor lying about, you could buy the much cheaper static and "upgrade" it to a rotary yourself?

 

[Lewis_RX8]

If it helps... their rotary is basically a static with an ac motor connected to give you a more "normal" 3-ph supply with no need to switch settings, and no minimum motor load (which statics do, which can be a pain if you want to run small feeder motors etc before the main kicks in).
In our old workshop we had a Transwave static hooked up to a pilot motor, and it ran even the big heavy old 7.5kw metalworker no bother.
So... if you have a big ole 3ph motor lying about, you could buy the much cheaper static and "upgrade" it to a rotary yourself?

Yea that would be nice to just have what is like a standard 3 phase plug in the workshop to run anything else off it opens more options for machinery having a standard 3 phase supply installed. Good to hear it runs 7.5kw but suppose its dependant on what the transwave is rated for.

unfortunately not got a motor however would be able to find one then would need somewhere to put it hmmm.

Decisions decisions

 

[Ubique]

Yea that would be nice to just have what is like a standard 3 phase plug in the workshop to run anything else off it opens more options for machinery having a standard 3 phase supply installed. Good to hear it runs 7.5kw but suppose its dependant on what the transwave is rated for.

unfortunately not got a motor however would be able to find one then would need somewhere to put it hmmm.

Decisions decisions

I would've thought as long as it's appropriately IP rated, it could be outside in it's own little enclosure, I see no reason why it'd need to be directly next to the Transwave.

 

[Munkul]

Lewis, I have glossed over some of the posts in this thread but my understanding is that you want this VFD/converter to primarily power the Triumph lathe?

IMHO, just buy the VFD and crack on with it you only have two motors on the Triumph, the main drive motor and the suds pump. You could replace the suds pump with a 1ph or drive it with a seperate cheap-as-chips VFD.
Pull out the contactors and relays from the panel. Install inverters. Rewire the start/stop switches into the inverters - job done. Put an additional potentiometer in the front to control speed, and mark a couple of points for frequency 50hz, and up and down. Done

That's what I would do, anyway.

 

[GRW]

Yea that would be nice to just have what is like a standard 3 phase plug in the workshop to run anything else off it opens more options for machinery having a standard 3 phase supply installed. Good to hear it runs 7.5kw but suppose its dependant on what the transwave is rated for.

unfortunately not got a motor however would be able to find one then would need somewhere to put it hmmm.

Decisions decisions

The thing with any ph conv (as T-wave would tell you) is if you put rubbish in, you get multiplied rubbish out.
So you need a good mains voltage, and if you have that, make best use of it. I.e. a meaty bit of cable so you have no volts drop to the Conv input.
Ideally I used to suggest that keep the feed to the Conv as short as poss, and then run a longer 3ph output if you need to to the load.
The pilot motor is normally mounted right next to the Conv, with a stub plate over the motor output shaft for safety.

 

[Ubique]

Yes, a vfd can do the same - when slowing a motor down it can regenerate from the motor, it gets dissipated into the dc bus but you can get braking resistors to dump more energy into during heavy braking if required - this is how they can stop a load quicker than just removing power and freewheeling. Most vfd now are whats called 4 quadrant drives, where they have this capability, in the olden days when they first appeared the cheaper ones were known as 2 quadrant drives, ie they could only accelerate but provided no braking torque.

Having just done a quick Google of solar inverters it seems to me that most will employ a transformer somewhere to do the voltage boosting. In that respect I can't see how they are much different to a vfd which boosts the voltage other than the solar has a fixed range of parameters to work with (in terms of the output stage) whereas a vfd will need to constantly change these and its the input side which will remain constant (ish)...

What sort of inverters? the ones I know of have a MPPT of 100V to 800VDC which convert to 230/415VDC as required then into AC, clearly not something you can do with a transformer

 

[Hood]

Is it a Triumph 2000 or one of the earlier ones?

 

[Ubique]

Is it a Triumph 2000 or one of the earlier ones?

TR3 with any luck!

 

[Lewis_RX8]

Lewis, I have glossed over some of the posts in this thread but my understanding is that you want this VFD/converter to primarily power the Triumph lathe?

IMHO, just buy the VFD and crack on with it you only have two motors on the Triumph, the main drive motor and the suds pump. You could replace the suds pump with a 1ph or drive it with a seperate cheap-as-chips VFD.
Pull out the contactors and relays from the panel. Install inverters. Rewire the start/stop switches into the inverters - job done. Put an additional potentiometer in the front to control speed, and mark a couple of points for frequency 50hz, and up and down. Done

That's what I would do, anyway.

Yes all got a bit complicated here lol

Effectively yes that's it I have a triumph roundhead with a 7.5HP / 5.5kw motor power on a pallet coming tomorrow and just wondering how it will be powered. however, was thinking about doing some future planning and making the VFD useable for any bigger mill or similar 3 phase machine to open my options.

Suds pump is a non-issue that can be sorted quickly with a capacitor very small motor so just want to run one.

Main point of confusion was the 220 volts 3 phase a VFD creates rather than 440v but think that will work if anything a little less powerful but that will be fine as don't see using full 7.5 horses for now.

And for how cheap the VFD is and should be easy to return on amazon Its going to be worth a shot just to get going.

Is it a Triumph 2000 or one of the earlier ones?

Earlier roundhead style

Will keep this thread updated as I go to inform any future triumph owners lol

 

[Munkul]

If the motor can be converted to Delta windings in the connection box, then the 240v/415v is a non issue.

 

[daleyd]

What sort of inverters? the ones I know of have a MPPT of 100V to 800VDC which convert to 230/415VDC as required then into AC, clearly not something you can do with a transformer

I imagine exactly the same way an inverter welder uses a transformer. (Yes, even an "inverter" will have a transformer inside). They chop the dc up and produce high frequency ac (or synthesised ac) at something in the kHz region - the high frequency means the step down transformer can be much much smaller then a traditional welder where the transformer has to operate at 50 hz. The transformer in an inverter welder is genuinely tiny comparatively. After this the stepped down ac is rectified/smoothed and sent to the output.

So, there is a transformer there, just a small one. In any kind of power circuitry I can't see how you are getting from 100v to 800v (for example) without one?

 

[Lewis_RX8]

If the motor can be converted to Delta windings in the connection box, then the 240v/415v is a non issue.

That was the plan wire it up to Delta but I've seen some one has said about some older and bigger motors not being suited to that but not sure yet.

Ronan runs his off a VFD which is similar so think it should be alright

 

[Hood]

They are the best ones, the newer like I have are rubbish.
Anyway it looks like it has a clutch and the motor constantly runs which would mean it is a piece of cake to just put a VFD on and make a small control panel up if you wanted.
That is as long as it is not a 2 speed motor, if it is then you may not be able to run 240v and even if you can then you would just have to chose one of the motors speeds. There are VFDs that can have multiple motor setups in them but they are not cheap.

 

[Lewis_RX8]

They are the best ones, the newer like I have are rubbish.
Anyway it looks like it has a clutch and the motor constantly runs which would mean it is a piece of cake to just put a VFD on and make a small control panel up if you wanted.
That is as long as it is not a 2 speed motor, if it is then you may not be able to run 240v and even if you can then you would just have to chose one of the motors speeds. There are VFDs that can have multiple motor setups in them but they are not cheap.

It is the two speed motor

Would just choose one of the motor speeds and vary frequency maybe?