Options for bucking 250 volts to 220.

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Old 01-02-20, 01:57 PM
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Options for bucking 250 volts to 220.

I have a cnc lathe that requires 220 volts on a 3 phase 100 amp circuit. The building is providing 250 volts. What are my options? The manufacturer is saying I can run it this way but will be at the max tolerance for the machine and any spike in voltage could cause more sensitive components (like control boards) to fry.
 
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Old 01-02-20, 05:37 PM
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Nominal voltage for three-phase power is either 120/240v delta or 120/208v wye. The 120/240v delta will be 240 volts between phases and 120 volts between phase A and phase C. Phase B voltage will be 208v to ground/neutral.

Your options are to get a 240 delta to 120/208 wye three-phase transformer or get two 12/24v (or 16/32v) buck/boost transformers to reduce the voltage down closer to 220v. What you need will all depend on the machine you are connecting and if it requires a neutral.
 
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Old 01-02-20, 08:40 PM
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a cnc lathe that requires 220 volts on a 3 phase 100 amp circuit.
The lathe can't need 100A @ 3phase. That would be massive.
What is the ID plate amp requirement.
 
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Old 01-03-20, 08:13 AM
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The plate requests 96 amps (called it 100 just to round up since you can't get 96 amp breaker).
 
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Old 01-03-20, 08:19 AM
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Ironhand, thanks for the reply. Machine does not require a neutral. I have been looking at (2) 12/24 buck/boost transformers. I was hoping for a more economical solution but it appears this is about the only option I have. Do you know if all brands would convert the same? I found model T-1-11686 from Acme ($600 Grainger) will do 250 down to 227 and provide 137amps at that conversion. They also sell a Square D model 3S43F for $1,200. I am not sure why the massive price swing. Any ideas or suggestions? I was looking to stay as close to $400 as possible but am not sure where else to find one of these.
 
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Old 01-03-20, 10:51 AM
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Is that a European or Asian manufactured CNC machine? I don't recall ever seeing a 3-phase motor labelled for 220 volts.
 
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Old 01-04-20, 06:17 AM
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I don't recall ever seeing a 3-phase motor labelled for 220 volts.
I have seen some machines out of Japan requiring 220v.

A buck/boost transformer(s) only needs to carry to the difference of the load you are running. According to the info I am seeing online it appears that you need 2 3kva buck/boost transformers. You should confirm this.

I have not seen any differences between brands of transformers and they all do the same job. Transformers have no moving parts and generally last for 50 years or more. I would not hesitate buying used ones from a local used equipment dealer.
 
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Old 01-04-20, 12:15 PM
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You may see aluminum vs copper windings.
 
 

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