I have never dealt with them … but they tell a good story !

On-message, if a little ‘shouty’ 🙂

https://www.drivesdirect.co.uk

MichaelG.

I have a 5hp 240 single phase to 415 three phase inverter from Drives Direct running my lathe and mill. It has worked flawlessly for many years. Others will chime in on the inherent flaws of these inverters but, I would buy a replacement if it failed.

Wade

A second and more recent UK supplier of the same device as Drives Direct is JFK Electrical, based in Northern Ireland.

I, too, have had a Drives Direct unit for many years and would similarly replace it like-for-like if the magic smoke appeared tomorrow.

Is it permitted to say that there are now (Amazon and Ali) many suppliers of 230v single phase in 415v three phase out VFDs? Thay are a lot more reasonably priced than ‘digital’ ones. XSY-AT4 is a generic model for them. Three individual boxes (one for lathe, one for mill, one spare) could be more economic than the suppliers above.

If you really want to buy new then I don’t think DriveDirect are particularly expensive and if they’re as good as their word, you’ll get support for your money.

However, I’d recommend taking a look on eBay for second hand VFD’s (Variable Frequency Drives, AKA inverters). If you stick to the good brands, you don’t have to worry about second hand VFDs not working.  VFDs either work or they don’t, and if they don’t work, you get a refund.

Paul of Haxby Shed fame on YouTube is fond of the IMO Jaguar Cub VFDs and they can be found for quite reasonable prices on eBay.

Other reputable names are Allen Bradley, Lenze, Mitsubishi and Siemens.  Delixi are a Chinese brand, but their VFDs are aimed at industrial usage, so they are supposed to be reasonably close in reliability to the Western makes.

One other important thing to consider is loss of torque at lower frequencies.  With the cheaper/older VFDs this was more of a problem.  Newer models tend to have what’s known as SVC mode (sensorless vector control) which can adjust the voltage in line with the frequency and other parameters.  You probably want SVC on any VFD you get.

In any case, it’s still suggested that one should go up a size in VFD, to give one some headroom. So for your 2 HP motors, you’d aim for a 3 HP capable VFD.

Now, I’m breaking that rule on my lathe as I have a 2 HP 3 phase motor with a 2 HP VFD, but then my lathe is a Warco 918 (so the old Taiwanese generic 9×20) and I got the 2 HP motor dirt cheap.  The clutch on this lathe is going to start slipping long before I ever even get near using 1.5 HP, let alone 2 HP!

One final thing.  Someone will come on this thread and suggest Newton Tesla.  Now, I’m sure they offer a good all-in-one solution, and offer good support but I consider them really rather overpriced.  Buying a VFD to suit an existing motor or buying both a VFD and a 3 phase motor, setting up an enclosure with the necessary filters and breakers, and doing the wiring isn’t really that difficult and ought to be something any of us here should be capable of.  It just takes a bit of information-finding, and some thought.  It feels like Newton-Tesla are trading on people’s lack of self-confidence to sell their packages, at what I consider to be an inflated price.

On 17 February 2026 at 17:28 southernchap Said:

….One other important thing to consider is loss of torque at lower frequencies.

I am afraid that is incorrect; there is not a loss of torque, but a loss of power.

Consider a 3-phase induction motor running at base speed. In the UK that is the speed at 50Hz. At base speed the full applied voltage is just sufficient to cause the rated current to flow in each winding. As the frequency decreases the voltage needed to cause the rated current to flow drops so the VFD will reduce the applied voltage to keep the rated current flowing. To a first approximation motor torque is proportional to motor current.

Since the current is constant as the frequency decreases the torque stays constant as well. However, since the speed decreases in proportion to the decrease in frequency the power produced also decreases.

To summarise, at speeds below base speed the torque stays constant but power decreases.

Cheaper VFDs use scalar control, aka volts per Hertz control. This is open loop and follows a V/f curve. In other words the applied voltage reduces as the inverse of the frequency. Very simply half the frequency needs half the applied voltage. Scalar control is simple to implement but runs into problems at low frequencies when winding and rotor resistance become significant and the V/f curve is no longer a good fit.

Vector control, aka field oriented control, is very different. The mathematics is quite complex but essentially involves transforming the rotating vector with time varying parameters, inherent in an inductor motor, into a two dimensional vector with time invariant parameters. The operation is known as the Park transform. In the transform space there are two currents in quadrature, D and Q. The D component controls field flux linkage while the Q component controls torque. The beauty of vector control is that the torque (Q) can be controlled directly in the model, and independently of D, without having to worry about what is actually happening in the motor windings.

Vector control can be open loop, sensorless, or closed loop with sensors. A limitation of the sensorless method is that there is a minimum frequency, around 1Hz, below which control is lost. For full torque at zero speed sensors on the rotor are needed.

Full torque at zero speed might not be needed on manual machine tools, but it is needed on electric vehicles which is where I gained my experience with VFDs and motor control.

Julie

Julie, thank you, that was a brilliant reply, no need to say sorry! 👍

I was vaguely nervous that my understanding and description in this post was significantly lacking on a technical level, and so it was.

I’ll need to do some more ‘homework’ on this subject, with your post as a starting point, because the feeling of an extremely fuzzy and inadequate understanding of a subject is a feeling I do not relish.

I’m entirely happy to be corrected as you have done in your post, as it gives me the kick to improve my comprehension.  So once again, thank you. 😊👍

Be very careful of doing a straight swap. The typical VFD needs a fixed connection to its load with no switches of any kind between VFD and load. There are VFDs and, I assume, fixed-frequency converters that can be connected like this but you must check with the supplier.

With my own three-phase lathe, I connected the VFD directly to the motor and was able to use spare contacts on the contactors to switch the control signals for forward/reverse to the VFD. But because there was no permanent three-phase available in the control box, I had to do a bit of rewiring to provide a separate supply for the control box (in fact, an external site transformer to give 110V). I even repurposed the inch/run switch to signal the VFD to go to 25Hz for a half-speed option.. This all works fine but not a trivial job!

Bottom line – be very careful about what you are doing and make very sure that you get a VFD or converter that suits the way you are going to use it.

When one is talking 3Phase one tends to think 415V as the OP does. The modern single to 3phase inverter is supplying 220V – so simply fitting one will not work ! If the motors involved can be wired for Delta rather than star that’s fine – re wire and it works, BUT what control gear is being used? Another issue ! For someone who understands all of this it’s easy BUT highly dangerous for someone who doesn’t.  Just be careful.   Noel.