Wiring a single to 3-phase inverter.

[LandyManLuke]

Glad it's running

Now about that lathe...............

That's the same thought i've been having for ooooo about 6 months! still looking though.

[simonr]

Well done Les - great that it's working. You'll be able to use your inverter as an additional speed control too.

Now is the time to buy machine tools. I was speaking to a local used tool dealer who said they have sold nothing since Xmas and would do a deal on anything!

Si

[integerspin]

So who is that then, I might be up for another lathe or a Fobco 10/8. I spotted some floor and need to obliterate it.

I did ask on one of the inverter threads a few questions, no one replied. I am going to be buying one[an inverter] in a month or two.

I wondered if many use feedback signals? I would really like to be able to stop the spindle in the same place every

time for the toolchanger, no plans on refitting that right now though. I still have the original inverter but it's the size of a fridge and

has a massive heatsink on the back, so I guess it's not very efficient, it's was made in 1985.

[mickeyw]

Hi, thought I'd wake up this thread and find out how people have got on.

Having aquired a Colchester Student I am looking at inverters to run a 3HP motor. I have done a fair bit of reading about the various ways of getting 3 phases from one, but now my head hurts The inverter type seem to be the way to go.

I have come across this one, and am wondering if it'll do the job. Can anyone recommend any particular brand to go for/steer clear of?

Also how hefty a single phase socket will I need to run such an inverter?

Thanks,

[Mark]

Michael,

There is a chap who advertises on www.homeworkshop.co.uk and deals in refurbished inverters for the home market - I bought the one I use on my milling machine from him, and he was very helpful. Also far cheaper than buying a new one!

My 1500W inverter (~2HP) is rated to draw 20A.... It doesn't seem to draw anything like that, but that is what the input plate says...

hth

Mark

[LandyManLuke]

The inverter will only draw current if the motor needs the torque, no torque demand on the motor, no current from the inverter, and hence from the mains.

Along the same lines, you can run a bigger motor off a smaller inverter, if you don't need all the power, or torque.

Have a look at The Inverter Drive Supermarket - They have a wide range and pricing seems reasonable.

For any inverter, documentation is key, you will need to read and understand the commissioning procedure, and the documentation will contain rated input and output currents, as well as details on digital and analogue inputs/outputs etc.

In terms of recommending a manufacturer, I would personally recommend Siemens, but that's because that's what I'm familar with, but it really does come down to documentation, I'd buy the drive that was well priced, but with decent documentation. Without that you'll struggle to get it running.

What's the motor winding? Life will be easier if it can be wired for 230v delta.

[Les Henson]

Over a year now since I got mine (thanks again for everyone's help ) I've added a cross vice, which is pretty essential, and I've cured the lighting problem by buying a cheap LED desk lamp from B&Q, removed the base of it and mounted it to the drill so that it comes on when the drill is switched on. I also made a tool tray for it for drill bits, chuck key, cutting fluid, etc, etc. The inverter has a permanent memory, so even after it has been switched off for long periods - it still has the presets in it. The instruction book for the inverter might as well have been in chinese for all I know, so you need to understand what needs to be done. The set-up still works perfectly, and I'm just as impressed with it as when I first used it.

Haven't got round to buying a lathe though

Les.

[LandyManLuke]

The instruction book for the inverter might as well have been in chinese for all I know, so you need to understand what needs to be done.

Or send a few PMs

[simonr]

Along the same lines, you can run a bigger motor off a smaller inverter, if you don't need all the power, or torque.

My inverter is rated at 4.5 kw - 6Hp , connected to a 100A mains supply. My Bridgeport Interact has a 9Hp spindle motor and on the whole, it's happy - until I push the emergency stop button! Then the spindle controller puts everything it's got into stopping the motor and throws the 40A mains trip in the inverter! I guess that's fair enough though. It does stop alarmingly quickly.

Many inverters (and many motors) can be configured to be Star or Delta wired - it's worth making sure that either the motor or inverter can - otherwise you know what will happen!

Agree that Siemens are the best, but are priced pretty competitively. Also, they will do what it says on the tin. I've seen a few oriental offerings which claim rather more than their size would suggest - I suspect it's a bit like Ghetto Blasters in Dixons claiming to have 40kw Power Output ('peak music power' written very small)

Si

[LandyManLuke]

My inverter is rated at 4.5 kw - 6Hp , connected to a 100A mains supply. My Bridgeport Interact has a 9Hp spindle motor and on the whole, it's happy - until I push the emergency stop button! Then the spindle controller puts everything it's got into stopping the motor and throws the 40A mains trip in the inverter! I guess that's fair enough though. It does stop alarmingly quickly.

I'd normally have expected to be able to parameterise the E-stop decel rate. Does the inverter react to the e-stop directly or does the spindle controller just clamp the setpoint to 0? I don't know what inverter you've got but in that situation I'd normally be looking at DC bus over-voltage as the drive struggles to shed the energy its taking from the motor - often a braking resistor or re-gen drive would be used, or the ramp extended.

Many inverters (and many motors) can be configured to be Star or Delta wired - it's worth making sure that either the motor or inverter can - otherwise you know what will happen!

It's possible to run a 400v motor off a 230v drive, you just need to scale the v/f curve appropriately, and sizing the drive is a bit more involved. Described well here.

Agree that Siemens are the best, but are priced pretty competitively. Also, they will do what it says on the tin. I've seen a few oriental offerings which claim rather more than their size would suggest.

Moreover, Siemens inverters are typically rated for 150% output for 60s in 300s, which means you can still accelerate (requires torque, which requires current)a motor, even when it's larger than the nominal rated size of the drive. If you're looking at Micromasters, or G110s, don't forget that you'll need a BOP as well, and maybe a PC connectivity kit as well. Neither are expensive, but they do add to the total cost.

Luke

[ex_mod_90]

My inverter is rated at 4.5 kw - 6Hp , connected to a 100A mains supply. My Bridgeport Interact has a 9Hp spindle motor and on the whole, it's happy - until I push the emergency stop button! Then the spindle controller puts everything it's got into stopping the motor and throws the 40A mains trip in the inverter! I guess that's fair enough though. It does stop alarmingly quickly.

Many inverters (and many motors) can be configured to be Star or Delta wired - it's worth making sure that either the motor or inverter can - otherwise you know what will happen!

Agree that Siemens are the best, but are priced pretty competitively. Also, they will do what it says on the tin. I've seen a few oriental offerings which claim rather more than their size would suggest - I suspect it's a bit like Ghetto Blasters in Dixons claiming to have 40kw Power Output ('peak music power' written very small)

Si

Ah inverters something I know a little bit about.

Si. If its a normal inverter and the e-stop provides a controlled e-stop then generally the OFF3 function is used. However saying that Luke is 100% correct, if the stopping or ramp down time is too quick then generally I would expect over-voltage trips rather than tripping the mains.

What it sounds like is that the controller is a applying a DC braking current to the motor shaft, and thats whats pulling out the breaker. This braking energy should be able to be adjusted. As Luke said, if you let us know what type of device it is then we should be able to help.

If its Siemens then thats a bonus

Rich.

[simonr]

The spindle controller is a Control Techniques box. I've not looked to see if there is a dead stop (enable) line or if it's software / changing the 0-10v control to zero - but I'm going to find out soon as I'm going to convert it to Mach3 (Mach3 is like Megasquirt for machine tools).

You can change the spindle speed from 8000rpm to zero and it just ramps down nicely. If you push the stop button - it really stops dead. It looks like it's stopping within a couple of revolutions! It appears to be driving the motor full power in reverse until it stops. You get a similar reaction if you reverse the spindle without switching it off first.

You can set most things from the controller interface - but the display and UI are cryptic to say the least!

Si

[integerspin]

Think I should have asked about inverters here, rather than on a cnc forum;-)

I bought a few inverters, a pair of Moeller cos they were cheap enough to **** about

with[the inverters were less than the post!], one is single phase and the other is three phase

input. The single phase one I plugged in and checked with a coolant pump, seems to work but I have a

loooong document to read, once I have decided what to use it on.

I also bought a 4kw omron 3MV3 inverter to run the spindle on my mill. I connected it up,

turned it on and it did roughly what it says in the 356 page document, flashing the run light etc.

I was kneeling down next to the mill reading the pdf on my gobook. well I gave up after getting

the spindle to turn at around 33 rpm, definetly not as high as 45rpm. I got a oL2 error after a minute

or so.

I had reset it to run V/f and reset the max current to the motors plate setting for 52Hz, it gives

the voltage, rpm, Hz and current for 1500 rpm and 4000 rpm. At this point I went in and printed

the pdf[yes 356 pages] after doing that I had to find a folder[seems a pity to loose pages, or

get them all mixed up] and the only folder I could find had 4 holes, so I had to punch

loads of holes. yes I am putting off letting the smoke out?

Is there a most basic set of parameters you could set an inverter up to test, far as I can see I really

need to check/reset all the relevant ones.

I was hoping to verify the inverter worked properly, not yet planned how it's going to be switched.

I have overrides on the pendant for the spindle so will wire them just so I can go and make it spin

and marvel at a spinning spindle.

[mickeyw]

Hmmm, a few things to learn about. I shall Google Star and Delta wiring a bit later, unless someone here can explain it in idiot's English for me; also how to tell which, if not both, a motor is suitable for.

One thing is puzzling me - why would you need an inverter with 3-ph input?

[LandyManLuke]

Is there a most basic set of parameters you could set an inverter up to test, far as I can see I really

need to check/reset all the relevant ones.

Look in the documentation for a 'quick commissioning procedure' or similar. It normally walks you through resetting the inverter to factory defaults, inputing the motor data, and then selecting the source of the control signals (the front panel, digital inputs etc)

Hmmm, a few things to learn about. I shall Google Star and Delta wiring a bit later, unless someone here can explain it in idiot's English for me; also how to tell which, if not both, a motor is suitable for.

Star and Delta are two ways of connecting the motors three windings, to each other, and the inverter. How you make this connection changes the voltage and current the motor will use. The rating plate on the motor will likely have to sets of figures for current and voltage etc, with either a triangle (delta) or three legged star.

The practical side of this is how the phases are brought out to the terminal box, and how the links are placed.

One thing is puzzling me - why would you need an inverter with 3-ph input?

3ph - 3ph inveters are actually more common than 1ph-3ph. the main use of inverters is to provide variable speed control. As well as giving much better control over the motor than just switching it on and off, it also allows energy savings over traditional contactor control, as well as more advanced features, such as meeting safety regulations regarding how the motor is stopped, or ran at low speed etc.

[simonr]

3ph to 3ph are often called VFD's or Variable Frequency Drives - and as Luke said, they are intended to vary the speed of a motor. The output frequency determines the speed and is usually controlled by a variable voltage fed in - normally 0 to 10v - from the CNC controller or speed control knob.

Simple VFD's just vary the frequency, but more grown up ones use what is called Vector Phase Control. They have a feedback from the motor which tells the controller it's rotational position. A vector controller has the advantage that it can generate the max torque at zero RPM and can achieve a flat power curve over the rev range. You only tend to find these on bigger machines (and electric vehicles) though. The vector control means you can tightly control the applied torque as well as the speed.

Si

[LandyManLuke]

We do quite a few applications with inverters in closed loop speed (and often position) control, most typically with a TTL square wave encoder fitted to the back of the motor.

We often also use inverters in Vector Control, but without any feedback. The inverter runs a model of the motor and uses it as an observer to provide the controller with extra information. This can give really good performance without the cost of an encoder, as long as the motor data is accurate, and the control can be properly tuned on a non-varying load. If the load characteristic varies too much the observer doesn't replicate the real conditions that well and performance suffers.

[simonr]

There is actually a third way that uses the back-emf to interpolate the motor position. It's seen on a few brushless DC controllers as well. That requires no encoder.

My spindle has an encoder for speed plus one pulse per rev - but no servo positioning. For the rest of the conversion I'm using these rotary encoders on the axis servos. At the same time I'm putting in the control infrastructure for a further two axes for a bit of future-proofing.

Si

[integerspin]

Sounds similar to my motor setup. A single pulse mag pickup on the spindle

and a resolver in the motor. The motor resolver was, I imagine, used by the inverter

for vector control and the single pulse for spindle orientation for the tool changer.

Seems several people with mach and lathes are threading with just the one pulse per rev

spindle setups, I was going to fit an encoder to my spindle.

How many pulses per rev for your servos are you going for?

Are your amps analog or digital?

I got rid of all my original electronics, inverter the size of a fridge, amps the size of a large

packet of cornflakes. Everything had super large heatsinks, which I think went towards the 15KVA rating.

The inverter and the serovpacks had braking resistors.

My inverter runs a small motor great, my coolant pump[motor ~6inch diam by height], responds pretty

good though it gets a bit noisy over 200 hz;-) Checked all the V/f settings, the motor has V, I, Hz and RPM for

1500 rpm and 6000rpm on the plate, infact it gives them for 3.7kw and 5.5kw[30minutes]. With the max current set

as 3.7kw rating it oL2[inverter overload] errors before it can get near 50hz. That max current is above the

inverters rating, motor 50Hz 25 A 3.7w inverter rated 19A.

[Les Henson]

' A single pulse mag pickup'

used by the inverter for vector control and the single pulse for spindle orientation for the tool changer'

'one pulse per rev spindle setups, I was going to fit an encoder to my spindle'.

'Are your amps analog or digital? '

' V/f settings, the motor has V, I, Hz and RPM for

1500 rpm and 6000rpm on the plate'

'as 3.7kw rating it oL2[inverter overload] errors before it can get near 50hz. That max current is above the

inverters rating, motor 50Hz 25 A 3.7w inverter rated 19A.'

'back-emf to interpolate the motor position'

' control infrastructure for a further two axes for a bit of future-proofing.'

'most typically with a TTL square wave encoder fitted'

'3ph to 3ph are often called VFD's or Variable Frequency Drives '

I think you should all just shut-up to be honest

Les

[mickeyw]

All I want to do is make my lathe work in my garage so I can make some bits for my Landy! This subject seems a lot more complicated than it needs to be, surely

In this age of virtualised everything, can I use some virtual volts and virtual phases please? And can they be converted into actual spinning round motion?

I shall have a look at the motor info plate on Monday and probably ask some more Qs

[TheRecklessEngineer]

I was having a chat with one of my lecturers the other day. He has a 3 ph drill running on single phase, using an induction motor as a converter

The way he described it to me: You have a 3 phase motor, with one set of windings being driven from a single phase supply. The next phase is driven via a starting capacitor. The remaining phase is disconnected from the power.

From those three phases connections are taken to the motor which you wish to drive. The corresponding phase lead/lag due to the capacitor/inductance of the machine generates pretty passable three phase.

He said there was info on the web, however, I have yet to find any. Sounds quite intriguing though!

MickeyW: I happen to have a single phase to three phase inverter sat in my airing cupboard at the moment. I may be persuaded to part with it (240v, 1.5kW I think). I also have a 3ph to 3ph inverter if it is of any use to anyone.

[simonr]

Are your amps analog or digital?

I got rid of all my original electronics, inverter the size of a fridge, amps the size of a large fridge

My new ones are digital (http://www.cncdrive.com/content/dugong.htm) through a 'SmoothStepper' motion controller. The old ones were Control Techniques Midi Maestro's. I'm using these encoders on the servos which are digital and programmable for between 48 and 2048 pulse per revolution.

The amps and motion controller would all fit in a shoebox - this contrasts with the current control cab which is half a cubic metre.

I did a Mach3 conversion on my Lathe a couple of years ago - and it has been fantastic! Hopefully the mill will be just as good!

Si

[TheRecklessEngineer]

I did a Mach3 conversion on my Lathe a couple of years ago - and it has been fantastic! Hopefully the mill will be just as good!

Just Googl'd that. Wow. I want!

[LandyManLuke]

All I want to do is make my lathe work in my garage so I can make some bits for my Landy! This subject seems a lot more complicated than it needs to be, surely

In this age of virtualised everything, can I use some virtual volts and virtual phases please? And can they be converted into actual spinning round motion?

I shall have a look at the motor info plate on Monday and probably ask some more Qs

Sorry if the above puts you off, it shouldn't do. As long as the ratings plate on the motor shows the required info, and you get an inverter that it is well documented, you should have the motor running within an hour, no problems.

Most of that will be checking the motor and wiring, quick commissioning the inverter parameters should take about 15 minutes at most.