need a way to buck from 3p 495v to 3p 400v???

[jsack]

have a customer that purchased a metal slip rolling machine rated for 400 v 3phase
and the voltage reads on the meter 490-495 volts 3p
talked to machine tech and he stated that it is critical for the cnc part of the machine
thanks guys
jason in wyoming

 

[jim dungar]

have a customer that purchased a metal slip rolling machine rated for 400 v 3phase
and the voltage reads on the meter 490-495 volts 3p
talked to machine tech and he stated that it is critical for the cnc part of the machine
thanks guys
jason in wyoming

That is a pretty large range for a buck-boost. Does the machine need a neutral connection also (not uncommon with 400V equipment). You can make your own 480-400Y transformer with (3) standard 480V to 240V single phase units. Connect their primaries in DELTA and their secondaries in WYE. This arrangement gives you a secondary neutral point that can be grounded and allows you use of the primary taps (if your transformer has them). Otherwise if you have the time order a normal 480-400V 3-phase transformer.

Please note: I am using nominal voltages, your actual values will vary slightly (i.e. some 400V arrangements can actually be 380-415V).

 

[winnie]

A standard 'buck-boost' arrangement should be able to do this. The companies that make these transformers have selection tables and suggested circuit arrangements to go from the voltage that you have to the voltage you want.

*HOWEVER* a buck-boost arrangement cannot change frequency. Given that 400V is _not_ a standard voltage in the US, I strongly suggest that you check out the frequency rating of the machine in question. If you need to go to 400V 50Hz, then you are talking about a much more complex and expensive converter.

-Jon

 

[GeorgeB]

A standard 'buck-boost' arrangement should be able to do this. The companies that make these transformers have selection tables and suggested circuit arrangements to go from the voltage that you have to the voltage you want.

*HOWEVER* a buck-boost arrangement cannot change frequency. Given that 400V is _not_ a standard voltage in the US, I strongly suggest that you check out the frequency rating of the machine in question. If you need to go to 400V 50Hz, then you are talking about a much more complex and expensive converter.

-Jon

I 100% agree with Jon. In my area of expertise (well experience if not expertise<g>), much 50Hz machinery designed for 380-415 volts operates satisfactorily at 460/3/60. Much doesn't, especially if loads are not linear with speed, ie fans. With linear loads, a motor will be supplying 120% of nominal power. If TEFC, the cooling will be marginally better. If there is a hydraulic pump comprising a substantial part of the load, it may be wise to drop its displacement by 10-20%, or if variable, to limit it by a similar amount.

There is a slight chance that the induction motor driven loads are not rated for 1200/1800/3600, rather limited to 1000/1500/3000. This is not common if the manufacturer also sells to 60Hz locales, but may be true if they were strictly 50Hz suppliers.

Now another issue ... the CONTROLS. They are virtually certainly using either 24DC or 24AC if a modern machine. If DC, their power supply may be universal; the Siemens I see used very often are 360-550V. If AC, it is more likely transformer derived and MUCH more an issue; dual frequency coils on solenoids were often not used.

It would be very smart to contact the manufacturer of the system and ask. Intelligent engineering decisions can be made, but only with thorough knowledge of the system.