Such a weird transformation I'm not seeing many offerings. Any suggestions?
This is 60Hz to 60Hz at least.
Keith Cress
kcress -
This is 60Hz to 60Hz at least.
Keith Cress
kcress -
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What's your suggestion for transforming 380 --> 230/240V 1Ø
- Thread starter itsmoked
- Start date
davidbeach
Electrical
Not taking any time to look at catalogs, but if you can find a 480:277 single phase transformer that you can then tap down about 7.5% you'll get 237V from your 380. The trick is that you have to look at higher voltages. A 208:120 would give the same ratio as the 480:277, but would be designed for 3.47 V/Hz and you'd be operating it at 6.33 V/Hz, sure to saturate; while that 480:277 would be designed for 8 V/Hz and operated at 6.33 V/Hz and not have any trouble with it.
- Moderator
- #4
I love auto transformers.
A 120:240Volt transformer connected as an autotransformer will do 360:240 Volts.
A +5% tap will give a primary rating of 378 Volts and a secondary rating of 252 Volts.
Is that or a near compromize close enough?
Bill
--------------------
"Why not the best?"
Jimmy Carter
A 120:240Volt transformer connected as an autotransformer will do 360:240 Volts.
A +5% tap will give a primary rating of 378 Volts and a secondary rating of 252 Volts.
Is that or a near compromize close enough?
Bill
--------------------
"Why not the best?"
Jimmy Carter
- Thread starter
- #5
Sorry Wayne440;
Just a measly 1hp motor.
Great point davidbeach. Experimenting last week with a little control transformer I saw exactly the V/Hz problem using a 120V transformer on 240V for an auto experiment. I'll dig around for a 480:277. Though this is starting to look like a replacement motor might be cheaper.
Bill; You tell me, you're better at this than me.
1HP (FLA=8Amp) Really? We can string the 240 and 120 windings together and stick 380 across them and this doesn't blow the V/Hz?
I knew you guys would have some concoctions that would work.
Keith Cress
kcress -
Just a measly 1hp motor.
Great point davidbeach. Experimenting last week with a little control transformer I saw exactly the V/Hz problem using a 120V transformer on 240V for an auto experiment. I'll dig around for a 480:277. Though this is starting to look like a replacement motor might be cheaper.
Bill; You tell me, you're better at this than me.
1HP (FLA=8Amp) Really? We can string the 240 and 120 windings together and stick 380 across them and this doesn't blow the V/Hz?I knew you guys would have some concoctions that would work.
Keith Cress
kcress -
- Moderator
- #6
Hi Keith;
240 V + 120 V = 360 Volts. This should work on 380 Volts. If the transformer has taps, use the highest tap and you will get closer to 380 Volts. Given a choice between too low and too high, motors are happier with the voltage a litle high.
Bill
--------------------
"Why not the best?"
Jimmy Carter
240 V + 120 V = 360 Volts. This should work on 380 Volts. If the transformer has taps, use the highest tap and you will get closer to 380 Volts. Given a choice between too low and too high, motors are happier with the voltage a litle high.
Bill
--------------------
"Why not the best?"
Jimmy Carter
- Thread starter
- #7
Understood Bill! Makes sense now that I've thought about it over diner.
Keith Cress
kcress -
Keith Cress
kcress -
Wouldn't be cheaper to rewind/replace the motor instead of adding one more element?
Muthu
Muthu
- Moderator
- #9
The question is:
"Can we get close enough to the required voltages with a 120:240 Volt transformer connected as a 240:360 Volt autotransformer?"
You will have to decide. Is the voltage right on 380 Volts? If it's nominal 380 Volts and running a little low, no problem. If it is no,inal 380 Volts but running a bit high you may be too close to saturation.
I have to ask; How did you get stuck with 380 Volts in SoCal?
If this is three phase 380 Volts then you will have 220 Volts line to neutral. The 220 Volts can be easily boosted to 231 Volts or 242 Volts with a small 240:12 Volt transformer or a 240:24 Volt transformer.
A note on the use of taps:
I may have mis-spoke in a previous post. If the taps are on the 240 Volt winding, then +5% will raise the 240 Volt rating to 252 Volts but the 120 Volt winding will still be a 120 Volt rating. So the nominal rating will be 252 Volts plus 120 Volts = 372 Volts. That's probably OK for the 380 Volt connection but your secondary voltage will be a little over 252 Volts. That may be a little high for the motor.
An off the shelf solution may require compromises and judgement calls.
You may consider a call to Hammond Transformers. They list 380:230 Volt transformers. Whether a suitable transformer is available at a reasonable price in a reasonable time frame is another question.
Bill
--------------------
"Why not the best?"
Jimmy Carter
"Can we get close enough to the required voltages with a 120:240 Volt transformer connected as a 240:360 Volt autotransformer?"
You will have to decide. Is the voltage right on 380 Volts? If it's nominal 380 Volts and running a little low, no problem. If it is no,inal 380 Volts but running a bit high you may be too close to saturation.
I have to ask; How did you get stuck with 380 Volts in SoCal?
If this is three phase 380 Volts then you will have 220 Volts line to neutral. The 220 Volts can be easily boosted to 231 Volts or 242 Volts with a small 240:12 Volt transformer or a 240:24 Volt transformer.
A note on the use of taps:
I may have mis-spoke in a previous post. If the taps are on the 240 Volt winding, then +5% will raise the 240 Volt rating to 252 Volts but the 120 Volt winding will still be a 120 Volt rating. So the nominal rating will be 252 Volts plus 120 Volts = 372 Volts. That's probably OK for the 380 Volt connection but your secondary voltage will be a little over 252 Volts. That may be a little high for the motor.
An off the shelf solution may require compromises and judgement calls.
You may consider a call to Hammond Transformers. They list 380:230 Volt transformers. Whether a suitable transformer is available at a reasonable price in a reasonable time frame is another question.
Bill
--------------------
"Why not the best?"
Jimmy Carter
Keith,
Assuming single phase because you mentioned experimenting with a control transformer.
You have a 240V phase motor and are sending it to Brazil where they have 380V 60Hz? Because of so, that's the 3 phase voltage and they use a Wye system, so line to neutral is 220V. Your motor would be fine. Or did you somehow stumble across a 380V 60Hz single phase motor that you need to power here?
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
Assuming single phase because you mentioned experimenting with a control transformer.
You have a 240V phase motor and are sending it to Brazil where they have 380V 60Hz? Because of so, that's the 3 phase voltage and they use a Wye system, so line to neutral is 220V. Your motor would be fine. Or did you somehow stumble across a 380V 60Hz single phase motor that you need to power here?
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
- Thread starter
- #11
This is just a question someone asked me.
I first thought it was the MUCH more common 380V/50Hz and counseled "Don't bother. Change the motor"
It can only be Tahiti, South Korea, Philippines, or Brazil. Probably Brazil. I've suggested he just replaces the motor with a new one. Heck, WEG is made in Brazil.
Barring that, I've suggested the 240:120 auto-scheme, with the suggestion that the motor FLA not exceed 65% of the transformer's.
Jeff; I thought that might be the case but didn't' follow that line as he stated "across two phases 380V". I also looked around a bit but couldn't find a table that showed delta or star as being the common form. Thought I was lucky to find a list of common industrial voltages and frequencies.
Keith Cress
kcress -
I first thought it was the MUCH more common 380V/50Hz and counseled "Don't bother. Change the motor"
It can only be Tahiti, South Korea, Philippines, or Brazil. Probably Brazil. I've suggested he just replaces the motor with a new one. Heck, WEG is made in Brazil.
Barring that, I've suggested the 240:120 auto-scheme, with the suggestion that the motor FLA not exceed 65% of the transformer's.
Jeff; I thought that might be the case but didn't' follow that line as he stated "across two phases 380V". I also looked around a bit but couldn't find a table that showed delta or star as being the common form. Thought I was lucky to find a list of common industrial voltages and frequencies.
Keith Cress
kcress -
If you happen to have a 50Hz transformer of the right ratio available then it should be happy enough on 60Hz. That ratio is pretty common in Europe, especially in older pre-harmonisation equipment. The increase in hysteresis losses in the iron due to the higher frequency should be more than offset by the reduction in flux density.
- Thread starter
- #13
Now Scotty...
![URL]](https://res.cloudinary.com/engtips/image/fetch/w_800,c_lfill,q_auto,f_auto,g_faces:center/[URL unfurl="true"]http://i13.tinypic.com/4vgzclu.gif[/URL])
Why would I have such a weird xformer on the California coast?
![URL]](https://res.cloudinary.com/engtips/image/fetch/w_800,c_lfill,q_auto,f_auto,g_faces:center/[URL unfurl="true"]http://i42.tinypic.com/vpc46w.gif[/URL])
Keith Cress
kcress -
Keith Cress
kcress -
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