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Can anyone point me towards an "inexpensive" load reactor/filter which I can put between my vfd and the older emco motor? The motor is a 3ph 220v .81KW.
Sierra
|
Hi Sierra
The chokes / reactors will be heavy , even smaller one ? , so you want something not too far away? . .?
Suggest do a search along the lines of “ VFD load reactor I kW “ and see
I notice lots of stuff , new and used, on our well known auction site ?
Regards,
Carvel ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Sierra Tunafish Monkeymind
Sent: Saturday, March 22, 2025 6:55 PM
To: [email protected]
Subject: [emcoV10lathe] vfd load reactor suggestions?? Can anyone point me towards an "inexpensive" load reactor/filter which I can put between my vfd and the older emco motor? The motor is a 3ph 220v .81KW.
|
Thank Ye Carvel. I get confused with the voltage ratings on the ones I see listed at 4 and 600v and am unsure if I need something specific for 240v, or if they are rated for higher but limit it via some other parameters or settings?
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On Mar 22, 2025, at 1:11?PM, cwlathes via groups.io <carvelw@...> wrote:
? Hi Sierra
The chokes / reactors will be heavy , even smaller one ? , so you want something not too far away? . .?
Suggest do a search along the lines of “ VFD load reactor I kW “ and see
I notice lots of stuff , new and used, on our well known auction site ?
Regards,
Carvel ? ? Can anyone point me towards an "inexpensive" load reactor/filter which I can put between my vfd and the older emco motor? The motor is a 3ph 220v .81KW.
|
Hi Sierra
The choke / reactor is there in series to smooth out the current going through it , so the voltage rating is just an insulation issue
So the voltage rating must be equal to or higher than whatever voltage your VFD is pushing through it
Am I making any sense ?
Carvel ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Sierra Tunafish Monkeymind
Sent: Saturday, March 22, 2025 10:47 PM
To: [email protected]
Cc: [email protected]
Subject: Re: [emcoV10lathe] vfd load reactor suggestions?? Thank Ye Carvel. I get confused with the voltage ratings on the ones I see listed at 4 and 600v and am unsure if I need something specific for 240v, or if they are rated for higher but limit it via some other parameters or settings?
On Mar 22, 2025, at 1:11?PM, cwlathes via groups.io <carvelw@...> wrote: ? Hi Sierra
The chokes / reactors will be heavy , even smaller one ? , so you want something not too far away? . .?
Suggest do a search along the lines of “ VFD load reactor I kW “ and see
I notice lots of stuff , new and used, on our well known auction site ?
Regards,
Carvel ? ? Can anyone point me towards an "inexpensive" load reactor/filter which I can put between my vfd and the older emco motor? The motor is a 3ph 220v .81KW.
|
So, as long as I find a 1kw choke/reactor, and it is rated at at least 240 volts, it does not matter if it is listed at 400 or 600 volts?
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On Mar 22, 2025, at 3:00?PM, cwlathes via groups.io <carvelw@...> wrote:
? Hi Sierra
The choke / reactor is there in series to smooth out the current going through it , so the voltage rating is just an insulation issue
So the voltage rating must be equal to or higher than whatever voltage your VFD is pushing through it
Am I making any sense ?
Carvel ? ? Thank Ye Carvel. I get confused with the voltage ratings on the ones I see listed at 4 and 600v and am unsure if I need something specific for 240v, or if they are rated for higher but limit it via some other parameters or settings?
On Mar 22, 2025, at 1:11?PM, cwlathes via groups.io <carvelw@...> wrote: ? Hi Sierra
The chokes / reactors will be heavy , even smaller one ? , so you want something not too far away? . .?
Suggest do a search along the lines of “ VFD load reactor I kW “ and see
I notice lots of stuff , new and used, on our well known auction site ?
Regards,
Carvel ? ? Can anyone point me towards an "inexpensive" load reactor/filter which I can put between my vfd and the older emco motor? The motor is a 3ph 220v .81KW.
|
Hi Sierra,
?
Sorry cant help with a inxpensive recommendation but you may want to check you VFD manual.? My TECO manual actually recommends NOT adding any capacitive, LC or RC components on the load side.? It does, obviously, recommend a reactor filter for the Line side for improving power quality - PFC and harmonics etc - and line thermal relays.
?
That said, I do understand the reasoning for some DV/Dt sine filtering on the load side for longer cable lenghts to prevent voltage spikes and, I guess more importantly for you, help prevent "laminar squeal" and deteriation of the winding insulation on older motors.? If the latter is the case then the best option, really, is to replace the motor with a inverter duty type, but that could come at a higher cost than a sine filter.
?
Anyway good luck.
?
Ross
|
Ha, this now has me as more confustercatededed than I was before…. except on tuesdays unless it’s Friday, with an added, better better not and soon? So much to consider and it’s hard to know
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On Mar 22, 2025, at 4:09?PM, Morepork via groups.io <ross.a.jennings@...> wrote:
? Hi Sierra,
?
Sorry cant help with a inxpensive recommendation but you may want to check you VFD manual.? My TECO manual actually recommends NOT adding any capacitive, LC or RC components on the load side.? It does, obviously, recommend a reactor filter for the Line side for improving power quality - PFC and harmonics etc - and line thermal relays.
?
That said, I do understand the reasoning for some DV/Dt sine filtering on the load side for longer cable lenghts to prevent voltage spikes and, I guess more importantly for you, help prevent "laminar squeal" and deteriation of the winding insulation on older motors.? If the latter is the case then the best option, really, is to replace the motor with a inverter duty type, but that could come at a higher cost than a sine filter.
?
Anyway good luck.
?
Ross
|
Sorry.? Maybe I should have started by asking what is the problem are you trying to resolve with a load reactor/filter???
?
Ross
|
I don’t want to fry the old/original Emco 220v 3ph motor running it on my vfd. It is an intermittent use mostly hobby machine, which goes from project to project as needed and sits between.
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On Mar 22, 2025, at 6:55?PM, Morepork via groups.io <ross.a.jennings@...> wrote:
? Sorry.? Maybe I should have started by asking what is the problem are you trying to resolve with a load reactor/filter???
?
Ross
|
Hi Sierra and Ross
Right? . .? today is Sunday so let’s see what we can do ?
Firstly to recap for Ross as to why we want to do this
The output of a VFD is a square wave of full voltage but varying interval
This output therefore consists not only of the 0 – 60Hz fundamental that the motor wants , but also a lot of high frequency high voltage components which can damage the insulation on older motors and cause motor failure
( In this discussion Carl reported two motor burnouts for this reason before he installed a filter ?)
One option when using a VFD with older motors ?is therefore to use a reactor to reduce these high frequency spikes
Newer motors with higher grade insulation are generally OK
Not all VFD’s are the same and differ in terms of the type of control circuitry and the type of output devices used ( MOSFET or IGBT’s ) so some VFDs are happy to look into a load reactor while others such as your TECO example might not be
Both my Yaskawa and Hitachi drives show load reactors as standard options? . .? see this example ?. . ..but check the owner’s manual for yours first ?
So to come back to Sierra’s question? , what is a reactor and what does it do ?
In this context a reactor is basically a choke which in turn is basically just a coil of wire wound on a laminated steel core
As such it has a certain inductance ( measured in millihenry’s – mH ) and exhibits a certain amount of “AC resistance” to AC current passing through it
HOWEVER? . .? this “AC Resistance” ?which we refer to as “Reactance” is proportional to frequency which is where the trick comes in
So low frequency current at motor frequency goes through virtually unhindered while the high frequency components encounter significant resistance and are therefore filtered out or at least reduced ?
So the gauge of the wire used must be heavy enough to carry the motor current and the insulation must be tough enough to withstand the spikes which it is being subjected to
For completeness , in the VFD literature we will also see reference to “ lineside reactors” ?
These are connected between the mains supply and the VFD on occasion ?
They can be used where the supply is noisy to keep such noise out of the VFD , or to stop noise generated by the VFD from feeding back into the supply and upsetting other sensitive equipment on the same circuit , but these do not normally feature in our applications
Hope this all makes some sense
Carvel
?
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From: [email protected] [mailto:[email protected]] On Behalf Of Sierra Tunafish Monkeymind
Sent: Sunday, March 23, 2025 2:38 AM
To: [email protected]
Subject: Re: [emcoV10lathe] vfd load reactor suggestions?? Ha, this now has me as more confustercatededed than I was before…. except on tuesdays unless it’s Friday, with an added, better better not and soon? So much to consider and it’s hard to know Sierra
On Mar 22, 2025, at 4:09?PM, Morepork via groups.io <ross.a.jennings@...> wrote: ? Sorry cant help with a inxpensive recommendation but you may want to check you VFD manual.? My TECO manual actually recommends NOT adding any capacitive, LC or RC components on the load side.? It does, obviously, recommend a reactor filter for the Line side for improving power quality - PFC and harmonics etc - and line thermal relays. That said, I do understand the reasoning for some DV/Dt sine filtering on the load side for longer cable lenghts to prevent voltage spikes and, I guess more importantly for you, help prevent "laminar squeal" and deteriation of the winding insulation on older motors.? If the latter is the case then the best option, really, is to replace the motor with a inverter duty type, but that could come at a higher cost than a sine filter.
|
Sierra,
?
If you’re looking for cheap, I have a DIY choke idea for you. The concept design came from a project I was researching to convert a straight AC welder to DC output, so the purpose of the choke was to help smooth the output of a bridge rectifier. I don’t know how if its capabilities falls within the range of what’s needed to protect your motor from the high voltage in your situation, but maybe Carvel or others can chime in to add their expertise to either say it won’t work, or possibly suggest tweaks to make it work. The design centers around the transformer from a scrap microwave oven. You cut the weld on each side of the transformer that holds the two halves of the laminations together. This allows you to remove the two coils and replace them with a single coil that can handle the current it needs to pass. In the case of the welder this choke is in series with the stinger of the welder, so it has to carry in the range of 100 to 200 amps, big wire, so you can only get about 9 wraps of wire, but this was supposedly sufficient. In your case you can use much smaller wire which allows more wraps and as a result better smoothing of the signal. Just thinking off top of my head here, but the primary coil originally in the transformer might have enough ampacity for your application. Maybe you won’t even have to cut it apart and install a new coil, just wire through the primary side of the transformer. I’m sure that the number of coils affects the inductance, and that in turn likely affects the frequency that it filters out, but how to figure that out I have no clue.?
Ok people who know the electrical theory please comment. It’ll be cheap but it might not work. Oh and I guess you’re going to need three of these, one for each leg coming off the VFD? Remember though, they're cheap. They’re on the side of the road all the time. I happen to come across something saying that treadmills have chokes on their motors, so that’s another possible source that you can scrap from things people throw away. Search microwave oven transformer on YouTube and you can find all sorts of fun things they’re good for.?
Bill Nite (knows enough electrical to be dangerous)
|
Hi Bill
An interesting idea ?
You would just need to find 3 transformers with intact primaries with the same inductance
Coincidentally this might even be in the correct ball park ?
I have a figure in my head for the VFD inductor of ?10-30 μH/kW? . . . maybe someone else can confirm? . . . and a quick search throws up values of 20-30 μH for medium size microwaves ? !
Just need to have someone with a multimeter that can measure inductance and start scrounging !
If you do go this route and leave the secondary winding ( unused for this ) in place just make sure the output terminals are well screened as you could have very high voltages appearing across them when there is current flowing through the Primary !
Regards,
Carvel ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Bill Nite via groups.io
Sent: Sunday, March 23, 2025 7:05 PM
To: [email protected]
Subject: Re: [emcoV10lathe] vfd load reactor suggestions? ? If you’re looking for cheap, I have a DIY choke idea for you. The concept design came from a project I was researching to convert a straight AC welder to DC output, so the purpose of the choke was to help smooth the output of a bridge rectifier. I don’t know how if its capabilities falls within the range of what’s needed to protect your motor from the high voltage in your situation, but maybe Carvel or others can chime in to add their expertise to either say it won’t work, or possibly suggest tweaks to make it work. The design centers around the transformer from a scrap microwave oven. You cut the weld on each side of the transformer that holds the two halves of the laminations together. This allows you to remove the two coils and replace them with a single coil that can handle the current it needs to pass. In the case of the welder this choke is in series with the stinger of the welder, so it has to carry in the range of 100 to 200 amps, big wire, so you can only get about 9 wraps of wire, but this was supposedly sufficient. In your case you can use much smaller wire which allows more wraps and as a result better smoothing of the signal. Just thinking off top of my head here, but the primary coil originally in the transformer might have enough ampacity for your application. Maybe you won’t even have to cut it apart and install a new coil, just wire through the primary side of the transformer. I’m sure that the number of coils affects the inductance, and that in turn likely affects the frequency that it filters out, but how to figure that out I have no clue.?
Ok people who know the electrical theory please comment. It’ll be cheap but it might not work. Oh and I guess you’re going to need three of these, one for each leg coming off the VFD? Remember though, they're cheap. They’re on the side of the road all the time. I happen to come across something saying that treadmills have chokes on their motors, so that’s another possible source that you can scrap from things people throw away. Search microwave oven transformer on YouTube and you can find all sorts of fun things they’re good for.? Bill Nite (knows enough electrical to be dangerous)
|
The goal is to have the magnetic fields linked.
Chris P
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Show quoted text
Hi Bill
An interesting idea ?
You would just need to find 3 transformers with intact primaries with the same inductance
Coincidentally this might even be in the correct ball park ?
I have a figure in my head for the VFD inductor of ?10-30
μH/kW?
. . . maybe someone else can confirm? . . . and a quick search throws up values of 20-30
μH
for medium size microwaves ? !
Just need to have someone with a multimeter that can measure inductance and start scrounging !
If you do go this route and leave the secondary winding ( unused for this ) in place just make sure the output terminals are well screened as you could have very high voltages appearing across them when there is current flowing through the Primary !
Regards,
Carvel
?
From: [email protected] [mailto:[email protected]]
On Behalf Of Bill Nite via groups.io
Sent: Sunday, March 23, 2025 7:05 PM
To: [email protected]
Subject: Re: [emcoV10lathe] vfd load reactor suggestions?
?
If you’re looking for cheap, I have a DIY choke idea for you. The concept design came from a project I was researching to convert a straight AC welder to DC output, so the purpose of the choke was to help
smooth the output of a bridge rectifier. I don’t know how if its capabilities falls within the range of what’s needed to protect your motor from the high voltage in your situation, but maybe Carvel or others can chime in to add their expertise to either say
it won’t work, or possibly suggest tweaks to make it work. The design centers around the transformer from a scrap microwave oven. You cut the weld on each side of the transformer that holds the two halves of the laminations together. This allows you to remove
the two coils and replace them with a single coil that can handle the current it needs to pass. In the case of the welder this choke is in series with the stinger of the welder, so it has to carry in the range of 100 to 200 amps, big wire, so you can only
get about 9 wraps of wire, but this was supposedly sufficient. In your case you can use much smaller wire which allows more wraps and as a result better smoothing of the signal. Just thinking off top of my head here, but the primary coil originally in the
transformer might have enough ampacity for your application. Maybe you won’t even have to cut it apart and install a new coil, just wire through the primary side of the transformer. I’m sure that the number of coils affects the inductance, and that in turn
likely affects the frequency that it filters out, but how to figure that out I have no clue.?
Ok people who know the electrical theory please comment. It’ll be cheap but it might not work. Oh and I guess you’re going to need three of these, one for each leg coming off the VFD? Remember though, they're cheap. They’re on the side of the road all the time.
I happen to come across something saying that treadmills have chokes on their motors, so that’s another possible source that you can scrap from things people throw away. Search microwave oven transformer on YouTube and you can find all sorts of fun things
they’re good for.?
Bill Nite (knows enough electrical to be dangerous)
|
I'd chisel or hacksaw-off the secondary... 2000V is not something one just shakes off and hobbyists sometimes tend to keep kludges outside of appropriate enclosures. No need to press out what is left of copper inside the core after you cut the exposed parts off. Broken microwaves are regularly found at e-waste and metal scrapping places. Transformers are usually undamaged.?
When taking one apart there are a few things to know 1. They contain a HV capacitor... usually it has a high value resistor in series so it drains in minutes to hours after being unplugged, but always assume the thing is alive and deadly. These also go up to 2000V. You can use a high value resistor across its terminals to drain the charge but you need to connect it with a known-good insulated pliers or similar tool. If you think the thing is discharged, confirm by sticking something metal across its contacts... needle nose pliers work pretty good. This tool also needs to be well insulated. And if it turns out the thing still has charge, you'll get a loud crack, big spark and a black mark on your tool to remind you of the event. 2. Magnetron contains two big and somewhat powerful ring magnets. These can be extracted, but they are secured with white or pink ceramic heat resistant material. Supposedly white is aluminium based and not particularly dangerous, but pink one is beryllium based and is a big health hazard if you inhale it (in dust form). I'm not sure how much of a risk this is, like if you'd have to sand the thing and sniff the dust or would just breaking the thing apart and being in the same room be enough. I also have no idea if color is actually tightly correlated to the material type, ie. if the white ones are always safe. In any case, do your own diligence if you plan to mess with one.
Carvel As I understand, MOT cores are made to run on the edge of saturation - they even have magnetic shunts to dump a bit of flux. Does this matters in our case?
Chris You want magnetic coupling in transformers and in common/differential mode chokes, but not in this case.
The goal is to have the magnetic fields linked.
Chris P
Hi Bill
An interesting idea ?
You would just need to find 3 transformers with intact primaries with the same inductance
Coincidentally this might even be in the correct ball park ?
I have a figure in my head for the VFD inductor of ?10-30
μH/kW?
. . . maybe someone else can confirm? . . . and a quick search throws up values of 20-30
μH
for medium size microwaves ? !
Just need to have someone with a multimeter that can measure inductance and start scrounging !
If you do go this route and leave the secondary winding ( unused for this ) in place just make sure the output terminals are well screened as you could have very high voltages appearing across them when there is current flowing through the Primary !
Regards,
Carvel
?
From: [email protected] [mailto:[email protected]]
On Behalf Of Bill Nite via
Sent: Sunday, March 23, 2025 7:05 PM
To: [email protected]
Subject: Re: [emcoV10lathe] vfd load reactor suggestions?
?
If you’re looking for cheap, I have a DIY choke idea for you. The concept design came from a project I was researching to convert a straight AC welder to DC output, so the purpose of the choke was to help
smooth the output of a bridge rectifier. I don’t know how if its capabilities falls within the range of what’s needed to protect your motor from the high voltage in your situation, but maybe Carvel or others can chime in to add their expertise to either say
it won’t work, or possibly suggest tweaks to make it work. The design centers around the transformer from a scrap microwave oven. You cut the weld on each side of the transformer that holds the two halves of the laminations together. This allows you to remove
the two coils and replace them with a single coil that can handle the current it needs to pass. In the case of the welder this choke is in series with the stinger of the welder, so it has to carry in the range of 100 to 200 amps, big wire, so you can only
get about 9 wraps of wire, but this was supposedly sufficient. In your case you can use much smaller wire which allows more wraps and as a result better smoothing of the signal. Just thinking off top of my head here, but the primary coil originally in the
transformer might have enough ampacity for your application. Maybe you won’t even have to cut it apart and install a new coil, just wire through the primary side of the transformer. I’m sure that the number of coils affects the inductance, and that in turn
likely affects the frequency that it filters out, but how to figure that out I have no clue.?
Ok people who know the electrical theory please comment. It’ll be cheap but it might not work. Oh and I guess you’re going to need three of these, one for each leg coming off the VFD? Remember though, they're cheap. They’re on the side of the road all the time.
I happen to come across something saying that treadmills have chokes on their motors, so that’s another possible source that you can scrap from things people throw away. Search microwave oven transformer on YouTube and you can find all sorts of fun things
they’re good for.?
Bill Nite (knows enough electrical to be dangerous)
|
Thanks Carvel, but my question was to Sierra as to the problem he wants to resolve by using a load filter, not what this does.? I'm well versed in principles of filters (reactor/chokes, sine filters, dv/dt filter etc.) being formally trained in power electronics - though this was many years ago:)
?
Why I asked Sierra this question is to try to understand if the filter will be used to allow the output from the VDF to be motor friendly, resolve issues with harmonics, or problems with cable resonance from long cable lenghts. This would help in deciding on what filter is require.
?
Harmonics will require a sine filter but if you just need to knock of the voltage spikes and so they are not reflected back, thus protecting the motor and VFD, then cheap dv/dt (EMC) filter should work - maybe even just a small inductor could work. Try also to keep the load cable as short as possible.?
?
There are are sine filters on Aliexpress if you want to go down that route.? Haven't used them so cant comment on their quality but they seem to be affordable. ?
?
Ross
|
I have an original (old) emco 240v 3ph motor which I am running via a vfd and I don't want to wipe out the motor's insulation from the vfd spikes. It is an intermittent us hobby machine, from project to project. Sierra
On Sunday, March 23, 2025 at 05:18:41 PM PDT, Morepork via groups.io <ross.a.jennings@...> wrote:
Thanks Carvel, but my question was to Sierra as to the problem he wants to resolve by using a load filter, not what this does.? I'm well versed in principles of filters (reactor/chokes, sine filters, dv/dt filter etc.) being formally trained in power electronics - though this was many years ago:)
?
Why I asked Sierra this question is to try to understand if the filter will be used to allow the output from the VDF to be motor friendly, resolve issues with harmonics, or problems with cable resonance from long cable lenghts. This would help in deciding on what filter is require.
?
Harmonics will require a sine filter but if you just need to knock of the voltage spikes and so they are not reflected back, thus protecting the motor and VFD, then cheap dv/dt (EMC) filter should work - maybe even just a small inductor could work. Try also to keep the load cable as short as possible.?
?
There are are sine filters on Aliexpress if you want to go down that route.? Haven't used them so cant comment on their quality but they seem to be affordable. ?
?
Ross
|
Hi Vedran
Don’t know what the B-H curve for Microwave Oven Transformer looks like . It would make sense to operate near saturation as that would give a constant voltage feed for the magnetron
Maybe one of our members with a spare transformer , a variable supply and a couple of multimeters could measure it for us
Don’t think it would impact this application as the value is not critical
Regards,
Carvel ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Vedran via groups.io
Sent: Sunday, March 23, 2025 10:47 PM
To: [email protected]
Subject: Re: [emcoV10lathe] vfd load reactor suggestions? ? I'd chisel or hacksaw-off the secondary... 2000V is not something one just shakes off and hobbyists sometimes tend to keep kludges outside of appropriate enclosures. No need to press out what is left of copper inside the core after you cut the exposed parts off. Broken microwaves are regularly found at e-waste and metal scrapping places. Transformers are usually undamaged.? When taking one apart there are a few things to know 1. They contain a HV capacitor... usually it has a high value resistor in series so it drains in minutes to hours after being unplugged, but always assume the thing is alive and deadly. These also go up to 2000V. You can use a high value resistor across its terminals to drain the charge but you need to connect it with a known-good insulated pliers or similar tool. If you think the thing is discharged, confirm by sticking something metal across its contacts... needle nose pliers work pretty good. This tool also needs to be well insulated. And if it turns out the thing still has charge, you'll get a loud crack, big spark and a black mark on your tool to remind you of the event. 2. Magnetron contains two big and somewhat powerful ring magnets. These can be extracted, but they are secured with white or pink ceramic heat resistant material. Supposedly white is aluminium based and not particularly dangerous, but pink one is beryllium based and is a big health hazard if you inhale it (in dust form). I'm not sure how much of a risk this is, like if you'd have to sand the thing and sniff the dust or would just breaking the thing apart and being in the same room be enough. I also have no idea if color is actually tightly correlated to the material type, ie. if the white ones are always safe. In any case, do your own diligence if you plan to mess with one. As I understand, MOT cores are made to run on the edge of saturation - they even have magnetic shunts to dump a bit of flux. Does this matters in our case? You want magnetic coupling in transformers and in common/differential mode chokes, but not in this case. ? ? The goal is to have the magnetic fields linked.
Hi Bill
An interesting idea ?
You would just need to find 3 transformers with intact primaries with the same inductance
Coincidentally this might even be in the correct ball park ?
I have a figure in my head for the VFD inductor of ?10-30 μH/kW? . . . maybe someone else can confirm? . . . and a quick search throws up values of 20-30 μH for medium size microwaves ? !
Just need to have someone with a multimeter that can measure inductance and start scrounging !
If you do go this route and leave the secondary winding ( unused for this ) in place just make sure the output terminals are well screened as you could have very high voltages appearing across them when there is current flowing through the Primary !
Regards,
Carvel ? From: [email protected] [mailto:[email protected]] On Behalf Of Bill Nite via
Sent: Sunday, March 23, 2025 7:05 PM
To: [email protected]
Subject: Re: [emcoV10lathe] vfd load reactor suggestions? ? If you’re looking for cheap, I have a DIY choke idea for you. The concept design came from a project I was researching to convert a straight AC welder to DC output, so the purpose of the choke was to help smooth the output of a bridge rectifier. I don’t know how if its capabilities falls within the range of what’s needed to protect your motor from the high voltage in your situation, but maybe Carvel or others can chime in to add their expertise to either say it won’t work, or possibly suggest tweaks to make it work. The design centers around the transformer from a scrap microwave oven. You cut the weld on each side of the transformer that holds the two halves of the laminations together. This allows you to remove the two coils and replace them with a single coil that can handle the current it needs to pass. In the case of the welder this choke is in series with the stinger of the welder, so it has to carry in the range of 100 to 200 amps, big wire, so you can only get about 9 wraps of wire, but this was supposedly sufficient. In your case you can use much smaller wire which allows more wraps and as a result better smoothing of the signal. Just thinking off top of my head here, but the primary coil originally in the transformer might have enough ampacity for your application. Maybe you won’t even have to cut it apart and install a new coil, just wire through the primary side of the transformer. I’m sure that the number of coils affects the inductance, and that in turn likely affects the frequency that it filters out, but how to figure that out I have no clue.?
Ok people who know the electrical theory please comment. It’ll be cheap but it might not work. Oh and I guess you’re going to need three of these, one for each leg coming off the VFD? Remember though, they're cheap. They’re on the side of the road all the time. I happen to come across something saying that treadmills have chokes on their motors, so that’s another possible source that you can scrap from things people throw away. Search microwave oven transformer on YouTube and you can find all sorts of fun things they’re good for.? Bill Nite (knows enough electrical to be dangerous)
|
Hi Ross
All noted , and thanks for the sine filter link
My “how it works” comments were directed more to Sierra
The theme of this discussion has been whether EMCO motors can be damaged by use with a VFD , and if so how to mitigate it
The Sine Filter option crept into the thread after Carl reported that after damaging two motors with his inverter , he had installed a sine filter and no further problems? . .? I agree that simpler things like a small inductor would help and that is how we got onto microwave oven transformers ?
Regards,
Carvel ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Morepork via groups.io
Sent: Monday, March 24, 2025 2:19 AM
To: [email protected]
Subject: Re: [emcoV10lathe] vfd load reactor suggestions? ? Thanks Carvel, but my question was to Sierra as to the problem he wants to resolve by using a load filter, not what this does.? I'm well versed in principles of filters (reactor/chokes, sine filters, dv/dt filter etc.) being formally trained in power electronics - though this was many years ago:) Why I asked Sierra this question is to try to understand if the filter will be used to allow the output from the VDF to be motor friendly, resolve issues with harmonics, or problems with cable resonance from long cable lenghts. This would help in deciding on what filter is require. Harmonics will require a sine filter but if you just need to knock of the voltage spikes and so they are not reflected back, thus protecting the motor and VFD, then cheap dv/dt (EMC) filter should work - maybe even just a small inductor could work. Try also to keep the load cable as short as possible.? There are are sine filters on Aliexpress if you want to go down that route.? Haven't used them so cant comment on their quality but they seem to be affordable. ?
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Maybe I've been living dangerously, but I've run that same motor (on a VP10) from a VFD with no load filter for 10 years with no hint of a problem. I also have a VFD on an old BP clone mill of similar age, also with no issues.
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Hi Len
Some VFD’s are noisier than others so you seem to have made a fortunate choice
It also depends on the motor’s history
The Emco motor tends to run hot so if it was previously in an environment where it was used a lot , then the insulation might also have suffered over time and be more prone to VFD or other spike damage
Lightning is also a hazard so not a good idea to use your machines in a storm? . .? also unplug them when not in use if in a lightning prone area like the one I live in ? ?
Regards,
Carvel ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Len Sherman via groups.io
Sent: Tuesday, March 25, 2025 5:10 PM
To: [email protected]
Subject: Re: [emcoV10lathe] vfd load reactor suggestions? ? Maybe I've been living dangerously, but I've run that same motor (on a VP10) from a VFD with no load filter for 10 years with no hint of a problem. I also have a VFD on an old BP clone mill of similar age, also with no issues.
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Sierra Tunafish Monkeymind
Morepork