VFD with a difference

[Piero]

Hi Guys

looking for a bit of info on this project of mine,

before I start, just for clarity, 230v in and three phase out of some VFD require a dual voltage motor

I do not have such motor on my Colchester bantam, NOR do I wish to change it

whats more, my 415v motor is a dual speed motor

It has run from a static phase converter but as some are aware, you only get two legs and a starter leg

What I am interested in learning more about is using the transformer from my static phase converter to produce the 415v input, and the running it through a 415v input 415v output VFD

Ive seen and read it is quite common practice.

my question is!!!! The 415v input VFD, would it not want to see three legs input, or does it not care as long as it gets 415v (lets say for two legs only)

 

[mark roberts]

The 'dirty' leg on my transwave static is 100v and the other two are 380v. Not sure if thats because its really old, 40years or its supposed to be like that. I run a a big old flat belt planer thicknesser via a vfd fed from the static. It used to bounce the hell out of the static trying to get the big head spinning but now its smooth.

 

[Mikes]

Sure my Transwave static unit has proper 3-phase output on each phase as it has a volt meter and selectable switch to measure each phase.

 

[Fazerruss]

Just fit a pony motor to your static then you will have a true rotary phase converter.

I have the same lathe and motor. It works perfectly

 

[Fazerruss]

Sure my Transwave static unit has proper 3-phase output on each phase as it has a volt meter and selectable switch to measure each phase.

That will only be when its running the machine. If you unplug the machine and measure the output on all three legs one will be zero. The machine motor is itself creating the missing phase. That's the principle behind RPC's



static with motors disconnected

 

[Agroshield]

Your idea involves buying a 415v in 415v out VFD.

It is possible to buy 230v in 415v out VFDs. In the UK, Drives Direct or JFK Electrical. Amazon has various Chinese offerings (https://www.amazon.co.uk/Variable-Frequency-Single-Controller-Inverter/dp/B08C7D8PP5).

With the dual speed motor, it is wise to take precautions so that you cannot switch the motor between speeds (which necessarily involves switching it through an off position) while the VFD output is active.

 

[Piero]

Without sounding harsh.

I asked about using the transformer from my static phase converter and running it prior to a 415v input vfd

I am exploring this option at the moment

Any information on this would be grateful

 

[Piero]

The 'dirty' leg on my transwave static is 100v and the other two are 380v. Not sure if thats because its really old, 40years or its supposed to be like that. I run a a big old flat belt planer thicknesser via a vfd fed from the static. It used to bounce the hell out of the static trying to get the big head spinning but now its smooth.

Fantastic

This is what I am looking to do

 

[Piero]

Sure my Transwave static unit has proper 3-phase output on each phase as it has a volt meter and selectable switch to measure each phase.

If it is a static and not a rotary, it can't have three legs

 

[Piero]

Just fit a pony motor to your static then you will have a true rotary phase converter.

I have the same lathe and motor. It works perfectly View attachment 522849View attachment 522850

Yeah that would work

But the motor is only doing what a modern 415v input vfd will do AND you are not powering two motors so it should be more efficient

 

[Piero]

Your idea involves buying a 415v in 415v out VFD.

It is possible to buy 230v in 415v out VFDs. In the UK, Drives Direct or JFK Electrical. Amazon has various Chinese offerings (https://www.amazon.co.uk/Variable-Frequency-Single-Controller-Inverter/dp/B08C7D8PP5).

With the dual speed motor, it is wise to take precautions so that you cannot switch the motor between speeds (which necessarily involves switching it through an off position) while the VFD output is active.

Yes

I cant argue there

Only I can find used 415v input vfds on fleabay quite cheaply

And I have the static with the 415v transform (prob 380v)

 

[Fazerruss]

Yeah that would work

But the motor is only doing what a modern 415v input vfd will do AND you are not powering two motors so it should be more efficient

The pony motor isn't under load so the current draw is very minimal.
The good thing about my setup is its basic and robust. I use my lathe on a daily basis and it never misses a beat. I can switch from low to high speed and vice versa and also turn on the suds pump.
You can pick up a used three phase motor cheap and its easy to wire up. It all works great.

I have a VFD on my milling machine and its works great. But, I do find it mildly irritating sometimes that it has a ramp up and ramp down speed when starts and stopping.
Sometimes I'm just impatient and want instant start up. It does however give variable speed which otherwise would be a pain to change over the belts in the head. I bought it off a fellow member who also configured it for me and its been superb. Its not a cheap Chinese one though.

 

[Seadog]

have a VFD on my milling machine and its works great. But, I do find it mildly irritating sometimes that it has a ramp up and ramp down speed when starts and stopping.

They are configurable parameters.

 

[Piero]

The pony motor isn't under load so the current draw is very minimal.
The good thing about my setup is its basic and robust. I use my lathe on a daily basis and it never misses a beat. I can switch from low to high speed and vice versa and also turn on the suds pump.
You can pick up a used three phase motor cheap and its easy to wire up. It all works great.

I have a VFD on my milling machine and its works great. But, I do find it mildly irritating sometimes that it has a ramp up and ramp down speed when starts and stopping.
Sometimes I'm just impatient and want instant start up. It does however give variable speed which otherwise would be a pain to change over the belts in the head. I bought it off a fellow member who also configured it for me and its been superb. Its not a cheap Chinese one though.

I will look into this as a option

But my static phase converter is not a know brand name model and I sometimes have to give it a phud lol

The 230v in 380v out vfd that was suggested earlier also sounds interesting, but I am un sure if that option (vfd) would run both speeds on my bantam

 

[Mikes]

If it is a static and not a rotary, it can't have three legs

Sorry, should have been more clear. It was the rotary one that I was talking about. This powers my lathe. I have a static one which powers a large drill press and on this you can see the voltage jump on the phase as it starts. This has an integral boost unlike the first one that I ever bought in the 1980's which had a sprung loaded toggle to give you a starting boost. All built in an ammo box and sold through Exchange and Mart. Very primitive and obviously wasn't a brilliant output as made the motor run hot.

 

[Mikes]

Yes

I cant argue there

Only I can find used 415v input vfds on fleabay quite cheaply

And I have the static with the 415v transform (prob 380v)

There are plenty of 3-phase vfds about as used throughout industry on pumps , fans etc . Used to regularly see them skipped when jobs were stripped-out as very few people want them 2nd hand. Generally very good quality as well with lots of the well known names (Siemens, mitsubishi etc.) so execellent value compared with Chinese tat.

 

[Piero]

This is my current static phase converter

It came with the lathe

It does require a tump from time to time as is buzzes a little funny and the lathe won't start

After a whack it works fine lol

 

[Brad93]

Do the job properly by making a rotary phase converter from your static one or use a 230v inverter and find the star point of your motor in the windings.

You will need a changeover switch between the inverter and the motor to switch between low and high speed. Its very important this switch is not operated while the inverter is running.

 

[Fazerruss]

This is my current static phase converter

It came with the lathe

It does require a tump from time to time as is buzzes a little funny and the lathe won't start

After a whack it works fine lol

It could be a problem with the potential relay sticking. These are used to turn on extra capacitors for the boost voltage that gives the motor an initial kick to get it spinning.
The relay failed on mine but after fitting the pony motor I realised it wasn't required anymore. The small pony motor is not under load so it spins up without boost capacitors. Then because this is already running and creating the missing 3rd phase it easily starts the lathe motor with ease even in top speed range and high gear selected.
Its turned out to be a very simple reliable setup. You'll notice i have VA meters on all three legs so I can make sure the phases are balanced within 20 volts. Some jobs I'm running the lathe almost continuously for 3 hours and neither motor gets hot.

 

[Piero]

Does anyone have any useful links on converting a static phase converter to a rotary phase converter

How would you size the dummy motor ???