Static phase converters

[Islander71]

I have been running a 3-phase Wadkin wood lathe for many years via an old Malden static single to 3 phase converter. Its pretty crude and doesn't give true 3-phase, so the motor doesn't develop full power, and it from time to time explodes capacitors.( Smell of burnt castor oil is seriously unpleasant!) I can fit a digital inverter/converter with speed control that gives true variable frequency 3-phase, but it costs about £600.
On Ebay there are Korean made digital phase converters at a reasonable price - https://www.ebay.co.uk/itm/28381645...FCQwPajYIEV1GWmnj10LNaIA==|tkp:Bk9SR_jVipHdYA
Again it uses the motor itself to generate the 3rd phase, so I dont know if it would be any better than what I have. Also the Malden converter on start up temporarily fires in extra capacitors to kick the motor into starting, something these DPS units dont appear to have, so I wonder if there would be any torque to start up.
Does anyone have experience of these units, good or bad?

 

[Seadog]

It looks like a standard VFD to me. It generates all three phases independently of the motor. It sounds expensive considering the other Chinese offerings.
For example - https://www.ebay.co.uk/itm/40099882...wrePBr8TaC&var=&widget_ver=artemis&media=COPY

 

[Stupoty]

I've had good experience with the HY brand ones ,

Genuine Huanyang 4KW 380V Variable Frequency Drive Inverter 5HP VFD HY Series 607885258191 | eBay

HUANYANG 1.5KW 220V VARIABLE FREQUENCY DRIVE INVERTER VFD 2HP 7A CE CERTIFICATED. Spindle Motor and Inverter VFD. UANYANG 4KW 220V VARIABLE FREQUENCY DRIVE INVERTER 5HP VFD FOR CNC HIGH QUALITY. 7.5KW 10HP 34A 220VVARIABLE FREQUENCY DRIVE INVERTER VFD New Arrival.

www.ebay.co.uk

They like to miss label them a lot , it's 220v

Stu

 

[addjunkie]

Add in an idler motor to your existing set up, helps smooth the whole thing out in the similar way to a rotary phase convertor does. Any similar sized motor will do!

Turing a static phase converter into a rotary

!!! I've got a chunk of that rubber, never even considered it as vibration damping. Brilliant! thanks for that idea I went begging to my mums to find a spare car floor mat but they were all too thin, then it dawned on me that we go through at least one rubber a season while the cows are in and...

www.mig-welding.co.uk

 

[Islander71]

Thanks for replies. Dont think the Korean unit I linked to is a VFD. It doesn't seem to alter frequency or voltage, so seems like a digital version of a conventional static inverter but without the transformer, or the extra capacitors for starting. So I dont see how it works.
I am a bit wary of the VFD inverters in case they interfere with the inverters I have connected to the mains from a wind turbine and solar panels. The turbine ones are 2 fairly old 2.5kw SMA Windy Boy units that go haywire when welding before shutting down, so obviously dont like any interference on the mains....
I could try adding an idling motor to what I have. The lathe motor is a 940rpm one - would the idling motor need to be the same speed?

 

[GRW]

Transwave's Rotary Ph Conv are basically a static transformer/capacitor converter + an idler motor. Benefits are no minimum motor size (unlike statics) and yes smoother as you're not relying just on the capacitor bank to generate ph3 as seen by your load item(s).
Also no need for switching settings as you do on a static for different loads/combinations.

 

[Martin-Sy]

I could try adding an idling motor to what I have. The lathe motor is a 940rpm one - would the idling motor need to be the same speed?

No, it can be any speed that you might have handy.
You don't say how big (in kW or HP) that the motor on the Wadkin is. Ideally the pilot motor should be bigger than the 'target' motor.
It's chalk and cheese BTW. I've run homebrew converters for 30+ years but adding a pilot motor makes everything much sweeter.

These days a VFD is the way to go but for 230V input you'll be looking at 4HP / 3kW maximum, and it will depend on being able to re-configure the motor for 230V delta connection.
There are some VFD's that do a voltage step up too, but they are more expensive.
HTH.
Good luck.

 

[Agroshield]

...Don't think the Korean unit I linked to is a VFD. It doesn't seem to alter frequency or voltage, so seems like a digital version of a conventional static inverter but without the transformer, or the extra capacitors for starting. So I don't see how it works.

It is a less sophisticated and more cost-conscious version of a standard VFD. Take the basic operation of of a VFD and remove all the unnnecessary bits (like variable frequency output, braking, reverse, etc.). It will take the incoming AC supply, rectify it to DC and then chop up that DC into (an adequate approximation of sine wave) 3-phase AC at 50Hz. In that respect, if a welder makes the wind and solar stuff unhappy, so too will this unit.

 

[Islander71]

Looks like my best way to go may be to replace capacitors again in the static converter and add a pilot motor and see what happens. The Wadkin motor is 1.5hp, it can be configured 220/240v or 380/420v, 4.7 or 2.7A. I do have another 1.5 hp 3-phase motor I could wire in as a pilot motor.
The link to the Vevor VFD doesn't quote £6,150 del. to me just the usual "Doesn't post to Scottish Islands"....
Thanks for all the information.

 

[Islander71]

Quick update. I tried adding in a spare 1.5hp motor as a pilot motor. It didn't seem to improve the converter, perhaps it would need to be a larger motor. I do have a 5hp motor, but think that would overload the Malden converter. On start up, the 1.5hp motor sees a surge of at least 17 amps - so the 5hp could maybe take about 55 amps to start! I was using a plug in energy meter to measure things. The 1.5hp lathe motor on its own sounded quietist on the Medium power setting, but the meter showed lowest amps and best power factor on the high setting. These were readings with lathe running but not under load without pilot motor.
Low setting 3.8A, power factor .45
Medium 2.95A power factor .58
High 2.3A power factor .85

 

[GRW]

Quick update. I tried adding in a spare 1.5hp motor as a pilot motor. It didn't seem to improve the converter, perhaps it would need to be a larger motor. I do have a 5hp motor, but think that would overload the Malden converter. On start up, the 1.5hp motor sees a surge of at least 17 amps - so the 5hp could maybe take about 55 amps to start! I was using a plug in energy meter to measure things. The 1.5hp lathe motor on its own sounded quietist on the Medium power setting, but the meter showed lowest amps and best power factor on the high setting. These were readings with lathe running but not under load without pilot motor.
Low setting 3.8A, power factor .45
Medium 2.95A power factor .58
High 2.3A power factor .85

Our made-up rotary converter used a motor that was at least 5hp (the static was a 7.5hp Transwave unit, made by Power Capacitors in the Midlands).

I think you need a pretty meaty pilot motor. Bead in mind also that although it's a big motor its running totally offload, so not drawing anything like its peak current once started

 

[dan.taylor.1]

Yeah the idler needs to be at least as big as the biggest motor you're running from the converter.

 

[m_c]

Quick update. I tried adding in a spare 1.5hp motor as a pilot motor. It didn't seem to improve the converter, perhaps it would need to be a larger motor. I do have a 5hp motor, but think that would overload the Malden converter. On start up, the 1.5hp motor sees a surge of at least 17 amps - so the 5hp could maybe take about 55 amps to start! I was using a plug in energy meter to measure things. The 1.5hp lathe motor on its own sounded quietist on the Medium power setting, but the meter showed lowest amps and best power factor on the high setting. These were readings with lathe running but not under load without pilot motor.
Low setting 3.8A, power factor .45
Medium 2.95A power factor .58
High 2.3A power factor .85

You ideally need to measure the phase to phase voltages, to establish what is giving the motor the most balanced power.
However when the motor sounds the smoothest, is as good a guide as any, without lots of measuring.


The problem with most capacitor based phase converters (be they static or rotary), is the ideal level of capacitance depends on the motor and the load.
Then there is the additional issue that you may get matched voltages, but due to how the capacitors interact with the motor(s), the false phase might not be peaking at the correct point.
Phase convertors are not a one size fits all thing, they're more a reasonable compromise that usually work pretty well.

 

[Brad93]

Stick a 230V Three phase motor on it and use a cheap VFD

 

[Brad93]

Oh your motor does 220V delta!
It's a no brainer. Spend £150-200 on a decent VFD and be done with it. Massive energy savings and will last years.

 

[Brad93]

Filtered VFD shouldn't cause any issues with your renewables setup.

I've had good results with the Parker drives but the Bosch are meant to be good too.

 

[GRW]

You ideally need to measure the phase to phase voltages, to establish what is giving the motor the most balanced power.
However when the motor sounds the smoothest, is as good a guide as any, without lots of measuring.


The problem with most capacitor based phase converters (be they static or rotary), is the ideal level of capacitance depends on the motor and the load.
Then there is the additional issue that you may get matched voltages, but due to how the capacitors interact with the motor(s), the false phase might not be peaking at the correct point.
Phase convertors are not a one size fits all thing, they're more a reasonable compromise that usually work pretty well.

With transformer & capacitor based pH conv- I was told with statics that you'll measure big variances between phases off-load.
It's important to ensure that any motor start circuits are running through Phase1, as its the only one that offers a correct voltage.

With a pilot motor I believe its a lot better, but it's still not a bad idea?

It's a long while ago....but there used to be Peter and one other guy with an unusual name that escapes me at Power Capacitors / Transwave - who were knowledgeable and helpful regarding their products, how they worked and how to select and get the best from a pH conv - and they made and sold a very good, reliable product.

 

[Islander71]

Filtered VFD shouldn't cause any issues with your renewables setup.

I've had good results with the Parker drives but the Bosch are meant to be good too.

View attachment 362897 View attachment 362898

Does "EMC" mean its filtered to not cause any mains disturbance? Or do you have to fit a separate filter of some kind? How effective is that?
The old wind turbine inverters do seem very sensitive to any voltage disturbance. At one time I fitted an electronic unit that used a clamp on the mains input cable to determine if current was flowing back into the mains in which case it used PWM - pulse width modulation - to put any excess into the immersion heater. Had to get rid of it as it caused the wind turbine inverters to shut down. If only the newer solar inverter was producing power it was not affected. Sold it on to a friend with new solar panels/inverter who says its brilliant.

 

[GRW]

Does "EMC" mean its filtered to not cause any mains disturbance? Or do you have to fit a separate filter of some kind? How effective is that?
The old wind turbine inverters do seem very sensitive to any voltage disturbance. At one time I fitted an electronic unit that used a clamp on the mains input cable to determine if current was flowing back into the mains in which case it used PWM - pulse width modulation - to put any excess into the immersion heater. Had to get rid of it as it caused the wind turbine inverters to shut down. If only the newer solar inverter was producing power it was not affected. Sold it on to a friend with new solar panels/inverter who says its brilliant.

Electromagnetic Compatibility or Compliance (EMC Directive etc) is something all kit and install are meant to comply with.... but I'm pretty sure lots of Chinese etc kit might well just be a Sticker lol.
Minimum standards of immunity to and emissions of harmonic interference etc.

Inverters (esp. older) tended to emit harmonics that would affect the voltage stability of Generators, and then due to their own sensitivity would refuse to operate on the affected supply that they'd caused.
I've seen UPS and Inverter-Charger units that'd work fine on Utility (much larger supply of course) but play up on Generator supply.
Also you could "damp out" harmonics and get stuff to stabilise by playing about adding Linear Loads like heaters.
The bigger the non-linear (Inverter or SMPS as a percentage of the supply rating, and as a percentage of the Load, the exponentially higher the liklihood of instability and operating problems.

Not long back I had a 600kva Generator as backup to large VSD Drive pumps, and part way into the pump cycle, they'd fail. Really, the Marelli Alternator wasn't a suitable type for the load, and voltage was dropping below the threshold for the Drive by about 9vac Ph-N.
It would have cost a Mint to replace the alternator/Gen or other , so I tried a dodge of turning the gen AVR up so there was another 10-12vac (from 230 to 242 I think) - which didn't solve the core issue but provided a work-around.... but it could just as easily have not worked. There are so many incalculable variables.