Step up power transformer and phase conversion

[rbrougha]

Is it reasonable to connect a 3ph 60 Hz 380V machine to a single phase 220V supply with 100amp capacity? (Deckel CNC universal milling machine model FP4NC )

The specifications I have about this equipment is the spindle power rating 2.0/4.0 kW. Also the total connected load (380V) is listed at 25kVA.

A rotary phase converter and step-up transformer may be the solution but how does one configure this power conversion equipment?

 

[jwerthman]

No, you cannot connect the three phase motor directly to the 220 volt, single phase supply. A solid state or rotary converter will be necessary between the 220 volt single phase and the 3-phase machine. You indicate that the voltage of your equipment is 380 volts, 60 Hz. I question the 60 Hz since most foreign voltages that are 380 volts are also 50 Hz. If that is the case, you will also need to make sure that your converter can change the frequency from 60 Hz to 50 Hz.

I don't think a 100 ampere, 220 volt single-phase supply will be sufficient. You indicate a total load of 25 kVA, which would be about 113 amperes at 220 volts, single phase.

 

[dydt]

hi..
380V supply goes with 50HZ..in europe for example...

don't you have a 220V, 3 phase supply?
are you trying to connect the machine in a residential service, because in a industrial establishment, 100A or higher is very common in 3 phase configuration.

dydt

 

[rbrougha]

Thanks for the feedback so far.

I am getting my information from a photocopy of a manual for a German made machine that I am thinking of purchasing. I now suspect that this information is wrong since the machine is presently operating in north america. I will request the actual electrical power requirements from the seller and ask the question again.

My service is single phase 220V and I have only ~100amps available to power a milling machine. Based on the previous reply I think that I will have a maximum power available of ~22kW. How much of this will be lost by using a rotary phase converter (1ph/220 to 3ph/220?

 

[busbar]

For US-based systems, [Of undoubtedly several] one abbreviated discussion is:

http://www.gwm4-3phase.com/u&s_elect.htm

http://www.gwm4-3phase.com/specmachines.htm

It may be worthwhile to peruse manufacturer’s literature for suggestions. Clearly, for your application their literature will tend to point to more-sophisticated assemblies, but some seem to have addressed specific, related needs and claim to have a track record for serving this type of industrial machinery.

In the US, typical utility character-of-service boilerplate may be: “Three-phase… service may be provided to a single-family residence for… use at nominal voltages of 120/240 or 120/208 volts at [our] discretion… [initially] billed to the customer to recover the costs of supporting three phase service… "

The other, possibly significant financial outlay is a [non-utility-furnished] transformer bank at the converter output, that would likely be something like a 220∆/380grdY configuration. Depending on ready availability, it may be fashioned with a set of 1ø units by a qualified, experienced installer. Depending on served-equipment power demand and voltage tolerances, an autotransformer bank may be cost effective. Phase conversion with integral voltage transformation is likely hen’s teeth.

It seems like in a number of regions, availability of acceptable 3ø power is impossible or prohibitively expensive. A lot seems to do with utility-rate structures, [zoning for some] and line-extension/facilities-upgrade costs associated with existing, localized line/transformer accessibility.

“Ask questions of several before you buy.” Detail your expectations in writing. The ‘shopping’ process may seem a bit daunting, but probably not impossible. As mentioned, the need for a stiff 1ø service complicates the matter to a degree. Discuss equipment and related “system” aspects—id est, utility-service+disconnection/short-circuit/overload-protection+wiring+converter+transformer+machinery characteristics and specifications with potential vendors, with the clear objective that you need a complete, readily useable, acceptably operational system—fully compatible with your electrical service and served load. {You may want to allow for a degree of later “expansion.” } Consider equipment enclosure withstand of materials like dust, coolant and metal particles. Realize that such equipment may affect things like overall building voltage regulation for motor/converter starting and running, space availability, maintenance needs, site noise level and heat load.

For the cited class of equipment, the advice dispensed in “rec.hobby.*” newsgroups is probably best given little credence.

 

[electricuwe]

For suppliers in Europe it is a common task to design a machines like that for operation at another frequency and voltage. There are two different approaches:

One is to design every machine with motors and other equipment for especially for the voltage and frequency at the customers site.

The other way is use use components that are suitable for 60 Hz as well as 50 Hz and that have very wide supply voltage range. This is usually done by using inverters on all motors and universal range switchmode power supplies. But for a machine of the rating mentioned I guess you will always need three phase power, regardless which approach Deckel used.

 

[dydt]

hi..
what is the size of the biggest motor?
is it possible to change the motors to single phase?
maybe it is cheaper to do this than get phase converter and transformers...

dydt

 

[jbartos]

Suggestions:
1. The 1-phase 50Hz AC to DC to 3-phase AC 60Hz converter is the most correct conversion for the given load. It will be more expensive than changing the 3-phase 60Hz motors to single phase 50Hz motors. The converter could potentially be used for a speed control.
2. Change 3-phase 60Hz motors to 1-phase 50Hz motors, will probably be less expensive with the following drawbacks:
2a. Single phase motors tend to be less rugged than three phase motors for the machine duty.
2b. The 1-phase motor physical dimensions will be bigger.
2c. The 1-phase motors are less efficient.

 

You may be OK on the load side if you use the roto phase and trans set up. We had the same sort of rig for many years, the soft start nature of the RP helped keep the UL side fuse from tripping (residential app) Helped reduce the inrush current spike. Your 25 kva is probably at max bit load. You may also be able to wrangle a bigger sngl phs trans out of the utility at no cost if your creative.