View Full Version : Hardinge HLV-H Rebuild - VFD Advice Requested

21-05-2021, 07:57 PM
Hi All,

I am planning the rebuild of a Hardinge HLV-H and as I only have a single phase supply was going to configure the power electrics in a similar way to that described by Bill Todd. The problem I am facing is identifying a suitable VFD as all the one's I have reviewed so far have a Low Voltage fault code for when a phase is lost. This would therefore cause a fault if I connect a single phase supply to the 3 phase VFD as one phase would be missing. Please correct me if my understanding here is incorrect. I have contacted a number of VFD suppliers and they are telling me that this configuration would not work. Can anyone advise me of a manufacturer that produces VFDs that I could use or have VFDs evolved so this can no longer be done?

I would very much appreciate your kind advise.


21-05-2021, 11:01 PM
Well, I don't know what Bill todd described but the function of most VFDs is to take a 230V single phase input and output 230V 3 phase power.
The problem comes when you want to Input 230V single-phase and get out 380/415V 3 phase, however, there are VFD's that will do this which can be bought from China and work very well.

22-05-2021, 09:09 AM
Yes, I suspect you're right. Most 230V in / 230V out VFDs don't check for phase voltages, 'cos it really doesn't matter to them. However, the type that boost 230V in to 415V out have front end which might get upset if a phase were missing if they use a 3-phase boost power factor corrector (PFC) front end.

I've avoided the need for one of those 230-415 VFDs but it must be possible to find some that DO run on single phase because I've seen a few recommended on various forums.
Sounds as if Jazz knows of some examples.

A simpler solution would be to either modify your existing motor for 230V delta connection or replace it with a 230V motor. Then you can use almost any 230V VFD. That may work out cheaper in the long run, as a boost VFD is going to cost you more.

22-05-2021, 09:51 AM
Hi Jazzcnc and Muzzer, Many thanks for your responses. Apologies as it looks like I have fallen into that trap of not providing enough information in my first post. The motor is a two speed motor and rated at 400v only so I was going to step up the voltage first then put 415v single phase into the 3 phase to 3 phase vfd. This is the configuration others have used but in their posts don't mention the vfd used. I know I cannot switch speeds when the motor is turning so this would need to be prevented within the circuit design. There was a thread I saw recently about fooling the vfd by creating the other phase using a capacitor but it didn't go in to sizing the capacitor or whether it had been successful. I would prefer not to go down the route of changing the motor if I can avoid it. Thanks again for your advice.

22-05-2021, 12:07 PM
Creating a third phase using a cap is only really sensible for a fixed load. You'd need different values for different loads, which isn't really possible on a machine tool. I have this on my coolant pumps but stick to VFDs for the spindle motors.

I had a 2 speed 415V on my lathe and have replaced this with a 240V motor. As you say, it's not possible to connect a 2 speed 415V machine in 230V delta. If you wanted to replace the motor with a single speed 230V equivalent, I'd suggest you go for a 2 pole motor (runs at ~3000rpm rather than 1500rpm off load) and increase the power rating while you are at it.

A modern TEFC (totally enclosed fan cooled) industrial motor will give more power in a similar space when compared to an equivalent open motor, if that's what you have. It also means you can use more of the VFD speed range and change gear less frequently. If you are going CNC, you probably don't want to be playing with too many ratios anyway.

I replaced my 1.5kW 2 speed lathe motor with a 5kW 2 pole motor (partly because I had one) and 5.5kW VFD. You might suggest that the machine isn't designed to handle that power but of course it's never going to get near 5kW and even the low speed peak torques aren't likely to bother it.

22-05-2021, 12:31 PM
HI Muzzer, thanks for the additional information. The lathe is fitted with an infinitely variable drive powered by a smaller motor (1/20 hp I think) which can be rewired to accept 240v so I was only really using the vfd as a phase converter and probably use the controls on the vfd. I'll look into changing the motor as you suggest as it may end up being a better solution.
Many thanks, Dave.

23-05-2021, 08:36 AM
If you are looking for 240V/1p to 415V/3p, then Ecogoo (see Aliexpress) do a range of them. A number of people on this forum seem to have used them with success.

My own lathe has a variable speed drive and electro-magnetic brake and given the poor access to the motor, a motor transplant would be quite a task. So it's driven by a 240-415V "thing." It's commercially-built (by a company no longer in business - that might tell you something) and uses a voltage-doubler arrangement feeding the VFD DC bus capacitor. The VFD is an ABB 415-415 device - pretty good quality. It all works fine in practice, but at higher loads the voltage on the DC bus cap sags between input mains pulses (half the usual frequency due to the voltage-doubler) and the VFD trips with the famous "missing input phase" error. And by higher loads, I mean when the lathe is wound up to more than about 2000 rpm (notional max is 2500). That's using the lathe's own speed control - VFD is left on 50Hz. I keep looking at the Ecogoo devices, but my machine is fine most of the time so haven't yet bothered.

Ecogoo are not that expensive - might be worth a look. Don't know who else does things like this. Be interested in Muzzer's comments on what might be inside their boxes -I'm curious!

24-05-2021, 05:12 PM
Hi Neale, Many thanks for your kind advice. The Ecogoo step up inverters look good and will definitely be the cheapest solution.