I have a wood lathe (Ejca TLS30) wich runs on 1 phase 230V, but the motor is a 3 phase motor, driven by a Hitachi inverter (HFC-VWE 2.5SBE) with stepless speed control. The lathe is 30 years old, but they still make them more or less unchanged.

The problem is that a few days ago it reduced the speed to less then half. The speed control (a 1K potentiometer connected to the iverter) still works as before, but with much lower speed. I've also tested the pontentiometer, and it gives plausible values.

With my limited knowledge on 3 phase motors I thought "hey, maybe the motor has lost a phase and runs on only 2 phases", but the mighty Google told me that in that case the motor wouldn't start at all.

My local supplier wants to sell me the inverter, without too much explenation on what might be the problem, but it's about $1400, which is a bit pricy, if the problem is the motor.

Does this sound like an inverter problem, or may this problem be related to the motor instead?

 

If you are lucky, it may be possible a parameter or two got corrupted?
Do you have the manual and do you have a back up of parameters?
You could set it to front panel run mode and see what the results are.
There are a few things you can check first.
Max.

 

$1400 (is that US dollars?) sounds very expensive for the inverter! Unlikely to be a loss of a phase in the motor or wiring because the motor probably would not start and the inverter would show an error indication.

First, you should get the inverter manual and go through the settings. Possibly after 30 years it's forgotten some of its settings. If you have to replace the inverter, go elsewhere and pay less!

 

Thank you for the tip!

Unfortunately I don't have anything but the lathe itself. I assume that front panel run mode applies to inverters with a display, which this one doesn't have? This one seems to be set up with the dip switches and potentiometers shown in the attached image. However I've found a manual for a similar inverter, so I guesss I'll try figuring out what the dip switches and potentiometers do and try fiddling with them.. Maybe I'm lucky and it's just a bad dip switch.

 

As a last resort there is the cheap $100 + Chinese Huanyang or the slightly higher, Hitachi, you don't need to pay $1,400 for a VFD now.
Check for proper pole count setting.
Max.

 

I've found some similar second hand inverters on ebay for around $300, so I'm not prepared for $1400 just yet. If I can't get anything useful from the manual and the dip switches I'll certainly have a look at the Huanyang.

 

The very first thing I suggest is to carefully check all of the connections of the present installation, and then carefully examine the present converter board. One failed connection could be the problem.

 

Thank you for the tip!

I assume that front panel run mode applies to inverters with a display, which this one doesn't have?

Yes just about all modern VFD's have a readout that can display various conditions, freq., current, and other status.
Max.

 

Sounds like you need to modernize. First look at the plate on the motor. Note the power (kW), phase current (A) and voltage (which will be close to your single-phase supply voltage). Most motors have two voltage settings depending if you connect it as star (high voltage) or delta (low voltage). This means there are two current values stated on the plate. Low voltage = high current and v/v. Yours should already be wired for the correct voltage. Then go to ebay or similar and buy a simple inverter (VFD). Hitachi, or another reputable make if possible will be good. Chinese if you have to! Make sure it comes with a manual or you can find one online.

The VFD not only allows you to run the lathe from a single-phase supply but you can program in a nice acceleration time for smooth starting.

 

As I examined that photo of the board, a component marked F514, I thuink, near the blue pot marked Max adj looked like it might have failed. A fuse is simple enough to check, if that is the problem then why? But replacing a fuse might be a cheap fix.

 

If this is the correct lathe, your spindle is 1.5kW. For $188 brand new, and from a reputable manufacturer, this is hard to beat (if you actually need a new VFD).

The speed dropping neatly in half might be a clue. Does it go from 0 to half speed during the first half of the pot turn, and then not go any higher for the 2nd half turn? Or does the complete turn of the pot now change speed from 0 to half speed? Are there any other symptoms? Inconsistent speed? Strange noises? Etc?

 

The other possibility if some parameters reverted to default, such as motor 2 to 4 pole etc!
Max.

 

Is your pot remote from drive. Id be looking to confirm loop voltages back to input terminal.

 

The OP appears to indicates the pot is remote, A 1k which seems a bit low, the most common value is 10k or Maybe 5k.
Max.

 

One more thing to investigate would be that adjustment pot, "Max.M". You could mark the present position and turn it a bit in either direction and see if that has an effect. Cheap parts like that sometimes develop strange values. An easy check to do, safe and simple.
After so many years it does not seem like a wiring error is likely. But I did suggest a careful examination of all the connections, that is still a good choice. AND, if there is a mains voltage selector switch, verify that it is still in the right position.

 

As I examined that photo of the board, a component marked F514, I thuink, near the blue pot marked Max adj looked like it might have failed. A fuse is simple enough to check, if that is the problem then why? But replacing a fuse might be a cheap fix.

The component is just a resistor, and I think it's better than it looks. I think it's just covered in dust, but I'll give it a closer look tomorrow.

One more thing to investigate would be that adjustment pot, "Max.M". You could mark the present position and turn it a bit in either direction and see if that has an effect. Cheap parts like that sometimes develop strange values. An easy check to do, safe and simple.
After so many years it does not seem like a wiring error is likely. But I did suggest a careful examination of all the connections, that is still a good choice. AND, if there is a mains voltage selector switch, verify that it is still in the right position.

I've found a more or less compatible manual for the VFD, and according to it the "m" in "m. adj" stands for monitor, and applies only to the optional remote control, which I don't have. It's for adjusting the frequency display on the remote control, I think. I've inspected all the external connections to the VFD and all the switches to the best of my ability, and everything looks fine.

If this is the correct lathe, your spindle is 1.5kW. For $188 brand new, and from a reputable manufacturer, this is hard to beat (if you actually need a new VFD).

The speed dropping neatly in half might be a clue. Does it go from 0 to half speed during the first half of the pot turn, and then not go any higher for the 2nd half turn? Or does the complete turn of the pot now change speed from 0 to half speed? Are there any other symptoms? Inconsistent speed? Strange noises? Etc?

That's the correct lathe, and the VFD you link is probably a good choice if this troubleshooting turns out to be a dead end. The speed of the lathe follows the complete turn of the pot. At minimum on the pot it goes really slow, and at maximum on the pot it's barely half the speed it should be. No other symptoms. A clue may be that it slowed down breifly one day before it became permanent.

The other possibility if some parameters reverted to default, such as motor 2 to 4 pole etc!
Max.

That might be so, but how do I set those parameters? I can't find any settings that apply to 2/4 poles.. There is a way of resetting the VFD, but I assume that brings it back to factory default settings, which isn't necessarily the correct settings for this lathe..




According to the manual this VFD has three different speed settings. The lowest speed is set by connecting CF1 (in the attached image) to L (not really visible in the picture). Medium - CF2 to L and max by connecting both to L. I still haven't tried this, as those settings haven't been used prior to this speed change either, but I guess I'll try it tomorrow, if no other revelation takes place.

 

It appears the only certain way is to try and obtain a copy of the original manual.
It appears to be older that the more modern way of setting all parameters digitally and is set up with other devices, pots etc.
The other malady that occurs with older VFD's such as this, is the large electrolytic's start to fail or lose capacity.
Is that a sign of slight leakage on one in the pic?
Max.

 

It appears the only certain way is to try and obtain a copy of the original manual.
It appears to be older that the more modern way of setting all parameters digitally and is set up with other devices, pots etc.
The other malady that occurs with older VFD's such as this, is the large electrolytic's start to fail or lose capacity.
Is that a sign of slight leakage on one in the pic?
Max.

I think the attached manual is just about right. I haven't noticed any leak from the capacitors, but I'll give them a closer look tomorrow as well. I have a distinct feeling this is going more and more in the direction of a new VFD...

 

Thanks for posting the manual, way to help us help you. Can give a lot better advice now.

Is your pot remote from drive. Id be looking to confirm loop voltages back to input terminal.

Yep. You need to verify that you have 10V between terminals H & L, and that you are getting 0-10V between terminals L and O, as you turn the pot.

If you don't have 10V on H&L then the drive's internal 10V supply is damaged or DS2 is set incorrectly (unlikely, unless you have rodents that like to flip dip switches in the night).

If you have the 10V on H & L but you're getting something other than 0-10V on L & O, then your potentiometer is bad.

If you're getting the 10V and the 0-10V but the drive is still slow, then something more serious is wrong. Check mechanical stuff first. Is the spindle hard to turn (motor overloaded)?

Do you have the full 230V at the input?

If all that stuff is good, then I think you need to replace the drive.

 

Given that the drive still provides a variable speed, evidently in a stable manner, a lack of diagnostic insight by those at a distance is not an adequate reason to decide to replace the drive. One more thought is the DC voltage that supplies the three phase inverter. The TS should check and verify that it is correct. Probably that is fed from a voltage doubeler, or maybe a bridge rectifier. If that voltage is much below the expected level then an open rectifier diode would be suspected. Replacing an open diode would be much cheaper than replacing the whole assembly, and probably less work as well.
So measuring that DC voltage is a next step in the diagnostics.