Which 3 phase inverter?


Help Support UKworkshop.co.uk:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Established Member
26 Sep 2016
Reaction score
Having just bought some 3 phase power tools, I now need a 3 phase inverter.

I struggle to understand 3 phase, so can anyone advise me on which are the best inverters to enable me to run two 3 phase power tools in my workshop please?
Your choice of inverter may depend on a few things.
no.1 What machines are these going on?
You may want a decent brand of VFD for a lathe for instance for torque at lower speeds, or if using a potentiometer (speed controller dial).
You might possibly (doubtfully) have a machine and want an instantaneous stop, which might turn the thread into what's the cheapest VFD with a braking resistor?
All VFD's have some capacity to stop quickly (its adjustable on all) depending on the inertia load, on my saws, I find I have no want for a mad stopping time, and don't try to challenge the circuitry on my cheap inverters, a few seconds is fine for me.
For a lot of machines you might choose not to spend a lot on one if you have no need for torque at low speeds, variable speed control by pot, braking resistors, or star wound motors.

No.2 Take a look at the motor nameplates, but take a look inside, unscrew the terminal box lid at the side of the motor more importantly.
You may see only 380/ 400v on the plate, but find its actually a dual voltage motor which is a common occurrence.

Dual voltage means either less complicated or less expensive, compared to a fixed high voltage motor (star, or Y symbol) because you can easily configure it in 30 seconds from high voltage to low voltage 220/240 volts, (called Delta, with a triangle symbol).

With a fixed star high voltage motor that's depending if your comfortable with digging out the windings to find the star point,
or if you want to fork out more money for a 380/400volt out VFD.
Memzey has done a thread on this here... getting a fixed star 380/400v high voltage motor to run on low voltage delta 220/240
makes it look easy...

I'm on a tight budget and have dual voltage motors in both machines I have
The Startrite 3hp saw has a Huanyang VFD, chosen because the fan runs all the time, and I only use the saw in sessions,
the "3 wire control" start and stop buttons are handy, because I made a hands free paddle switch so less complicated to achieve with push buttons, than with a toggle switch.
And my 3hp bandsaw has an Isacon/askpower on it because it has an auto shutoff feature for the wee computer cooling fan
inside, so it only hums away when the motor is activated, I use the bandsaw throughout the day in bits so don't want a fan on all the time.
Both are around 100 pounds
The Huanyang has a relay built in so can just stick a stop button and seperate a start button.
The Isacon/askpower needs a 5 quid relay inbetween which I haven't got, so I just stuck a toggle switch instead of buying that.
If you choose to go for a cheap VFD. and want to hook it up without fuss, get a brand which somebody has a guide to the parameters (exact motor commands) online somewhere, like here.
Myfordman, Robert/Bob/9fingers Minchin, has done a really thorough guide on these over at thewoodhaven2 .
He is an expert, and has an excellent PDF guide you should really read concerning VFD/inverters.
It will be at the bottom of his signature over at thewoodhaven2, I believe he's the mod there, so easy to find.

Bottom line
If both motors turn out to be dual voltage, and these machines are to be running at full speed
without need for a pot or instant stopping then you can buy whichever one you like.
If you don't need the machines running straight away, and one happens to be dual voltage, and one not, then it might be a good idea to buy the most straight forward one firstly, hook it up and see about how you feel after getting to know VFD's better, before hooking a more complicated one up. Read Bob's induction motor PDF.

Good luck
Thank you very much Tom for your work in that really helpful reply. Unfortunately, budget is the deciding factor. I need a 3 phase supply for my new pillar drill and Harrison engineering lathe.
There are a lot of Chinese VFD's on the market at great prices.
It is common in China for essentially the same design product to be made by many different companies in many different factories. Usually with a change of name and minor cosmetic differences. It's hard to predict the quality of these before or even after you receive them, but broadly, electronics made with more attention to detail and more quality assurance of the components and assemblies will cost more.
China can and does cater to every budget and will supply everyting from very low to very high quality if you're willing to pay for it.

My own choice was to try a UK brand. Invertek, who manufacture their own drives in Wales. The first one worked well, came with decent instructions and was nicely made so I've stuck with them and have fitted 6 or 7 to date. Some new, some second hand.
Do be aware that the (electrolytic) capacitors in (I would assume pretty well every) VFD can "go off" over time in storage so beware of using second hand VFD's or even a new one that has been sitting on the shelf for over a year without reading up on the subject of "re-forming" the DC link capacitors.
It's not the end of the world if an £80 drive blows but higher power, weather sealed units are a bit pricey, even second hand when you have little or no come back if they go bang ...
In case you are not aware you can't get one VFD to power the whole shop like you would with a rotary phase converter. If you try and switch the machine on using the machine's original switches you will let the magic smoke out of the VFD. They have to control the motor switching. If the motors on the machines are similar in size and usage then you can use one VFD but you will have to disconnect it from one motor and reconnect to the other. That's why for most installations there will be one VFD for each motor.

My VFD for my 5hp dust collector is from China from a company called Powtran. I bought through Alibaba but you can buy direct too.