a better bargain to be had when buying old three phase machines.
Phase convertor
- Thread starter Hpps
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swapping the motor might not be as simple as it sounds, might be a special mount, longer shaft or even imperial! Get the old one off and see.
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Sounds simple but you replace the three phase DOL starter with a single phase DOL and with the correct overload device set for your new motor. You could retain the old DOL if you can get a 230 volt coil for it but just as easy to replace with new one.
Hpps
Established Member
Hpps
Established Member
Ttrees
Iroko loco!
Can you get access to the terminal housing to see if those motors are actually "fixed star wound"
motors (see Bob's excellent induction motor write up on "the other place")
or whether either actually might be dual voltage with six terminals, plus the earth of course.
Something like below
There could even be schematics under the lid, explaining configuring either 380v "Star" high voltage,
or Delta 240v low voltage.
FYI, both those motors are of the two suitable speeds for VFD's, the blue tablesaw motor running twice the speed i.e it's a 2 pole motor, whilst the green one being a 4 pole motor.
Anything other than either of those pole numbers wouldn't be suitable for VFD's/inverters.
Not sure if those things matters for a plug and play digital phase converter?
It's probably in Bob's write up, haven't read it in quite a long time.
PS also worth noting there's folks on the ozzy, woodworking forums.com, who have been running star wound motors for lathes for some time with 380v out cheapo VFD's,
so might be worth finding, and seeing what folks here think about that here.
Tom
motors (see Bob's excellent induction motor write up on "the other place")
or whether either actually might be dual voltage with six terminals, plus the earth of course.
Something like below
There could even be schematics under the lid, explaining configuring either 380v "Star" high voltage,
or Delta 240v low voltage.
FYI, both those motors are of the two suitable speeds for VFD's, the blue tablesaw motor running twice the speed i.e it's a 2 pole motor, whilst the green one being a 4 pole motor.
Anything other than either of those pole numbers wouldn't be suitable for VFD's/inverters.
Not sure if those things matters for a plug and play digital phase converter?
It's probably in Bob's write up, haven't read it in quite a long time.
PS also worth noting there's folks on the ozzy, woodworking forums.com, who have been running star wound motors for lathes for some time with 380v out cheapo VFD's,
so might be worth finding, and seeing what folks here think about that here.
Tom
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guineafowl21
Established Member
Looks to be 400V (ish) delta, meaning you can’t convert it to run normally on 230V.
Ttrees
Iroko loco!
That one caught me out, I didn't expect to see the delta triangle symbol next to 380/400v
I thought most 380/400v motors which weren't dual voltage, were strictly "fixed star wound motors".
Is that phrase a nickname.
Not that I haven't seen evidence of a higher voltage 380/400v motor before, but those were odd really old ones, and not the regular 2 or 4 pole types.
Is the fixed star wound phrase only applicable to motors made beyond, say after the 1970's ?
Thanks, and apologies for my ignorance.
Tom
guineafowl21
Established Member
Fixed star just means the tri-connection (‘star point’) is buried in the windings and not available at the connection box. So you can’t convert them to delta without some surgery. Older, small 3ph motors tended to be made this way, since the manufacturers weren’t expecting anything other than 400V 3ph.
In this case, the motor is wound to receive 400V rather than 230V when in delta. This is often to permit star-delta starting, which is to reduce the inrush current, like a soft start.
For any 3ph motor, think of star as high impedance, delta as low. Impedance is like resistance, but slightly more complicated.
Using a switching arrangement, the motor is started in star (high impedance, lower current), then, when up to speed it’s switched over to full power delta.
In this case, the motor is wound to receive 400V rather than 230V when in delta. This is often to permit star-delta starting, which is to reduce the inrush current, like a soft start.
For any 3ph motor, think of star as high impedance, delta as low. Impedance is like resistance, but slightly more complicated.
Using a switching arrangement, the motor is started in star (high impedance, lower current), then, when up to speed it’s switched over to full power delta.
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why do people waffle on about star delta?
pickie of mount ideally.
guineafowl21
Established Member
I like star delta…
Those were the days before soft starters, we had no other way of starting large motors, you could not use DOL due to the huge inrush currents.
Don't forget we are talking about Ac and Inductance, therefore you cannot ignore frequency and this is why with a decent VFD you can run a motor in DELTA at 400 Vac to achieve better torque. Here 230 volts = 50Hz and 400 volts you need 87Hz to maintain the same current through the windings.
Don't forget we are talking about Ac and Inductance, therefore you cannot ignore frequency and this is why with a decent VFD you can run a motor in DELTA at 400 Vac to achieve better torque. Here 230 volts = 50Hz and 400 volts you need 87Hz to maintain the same current through the windings.
Hpps
Established Member
Still making no sense to me chaps.
Back to my original question - can I buy a thing to make these 2 motors work from my barns 240v supply or do they need new 240v motors?
Back to my original question - can I buy a thing to make these 2 motors work from my barns 240v supply or do they need new 240v motors?
My two penny’s worth. Since 1 April 2023 the electrical people can no longer charge for the infrastructure changes when installing 3ph into dwellings. So, the cost of attaching 3ph in the UK has significantly decreased for most installations. Looking to the future where some form of heat pump and electric car charging is highly likely to become the norm, then 3ph is almost essential. I think having 3ph will both increase the value of your home as well as increasing its desirability, so why not just install 3ph and have all the advantages?
be interetsing to see the prices people post here after asking their supplier for three phase.
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yes, the simpliest thing is a phase converter, available in static or rotary, rotary being better as it is motor run.
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A typical supply is the local sub receives 11Kv and a three phase cable supplies a housing estate, the houses being distributed across the three phases so each has a 230 single phase supply. Now if all these houses require a three phase supply for car charging and or heat pumps etc then the cable is undersized, the local sub probably has insufficient capacity and it may be the case that the 11Kv cannot handle extra load either so the problem grows arms and legs. Now think of many housing estates and new builds needing this three phase supply and the problem will probably go past your local DNO to the national grid because our electrical infrastructure is in need of huge investment and re stringing miles of overheads is not coming cheap and the cost of substations is enormous but it all ends at the point of generation, is there enough capacity to meet the load.
If you are not expecting to buy more three phase machines and each machine will perform properly on the power that a single phase motor can deliver then look at changing the motors, first step is to see if that machine was available in a single phase version and then it is much easier.
Totally agree, the infrastructure is pants! The green agenda of all electric cars and everyone using air source was dreamt up by someone smoking waky baky without a clue of the implications. But a friend has just had 80 KVA installed for £2K, and my quote is £5K, but I need much more extensive cabling. So get in quick before the capacity is diminished!
induction charging for the ev's from roads will be the norm. way off topic, the op is what is the easiest for two machines!!!!
