converting 220 volt single phase to 440 3 phase

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a.bisnath

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I need to supply a refridgerated container with 440 volt 3 phase at 25 amps, the only source available supply is 220volt single phase at 150 amps capacity.Any suggestions how to get this done?
 

Jraef

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If its temporary I would go with a generator.

Permanent will need a phase converter and a transformer.
There really aren't any other choices. On a container, sounds like it is temporary. The generator may be the best option, on less fuel is a problem.

If it is permanent, then you have various choices of phase converter options. With a hermetic compressor motor, those choices are further limited to either a Rotary Phase Converter (RPC), or an electronic phase converter, like a VFD or a "Phase Perfect" unit. Stay away from the Static Phase Converters because they basically just "trick" the motor into starting with single phase, but de-rate the motor capacity when running. That's OK for some loads, but will smoke your compressor on a refrigeration compressor.
 

Smart $

Esteemed Member
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..the only source available supply is 220volt single phase at 150 amps capacity...
Is that free and clear capacity or does it include other loads not mentioned?

If you are looking at permanent, you need to know. That 440V 3? 25A load converts to 220V 1? 87A load with no padding for conversion efficiency. If a single motor compressor load, it gets factored 125%, so you're looking at 108A calculated load minimum.
 

Besoeker

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Is that free and clear capacity or does it include other loads not mentioned?

If you are looking at permanent, you need to know. That 440V 3? 25A load converts to 220V 1? 87A load with no padding for conversion efficiency. If a single motor compressor load, it gets factored 125%, so you're looking at 108A calculated load minimum.
Not to mention starting current...........
 

Besoeker

Senior Member
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the capacity is free and clear no other loads
Hi Al.
Good to see you popping in.
My point is that the supply capacity has to be sufficient to start the compressor motor.
If it is a standard cage motor it can take upwards of six times FLC to start.
 

iceworm

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I need to supply a refridgerated container with 440 volt 3 phase at 25 amps, the only source available supply is 220volt single phase at 150 amps capacity.Any suggestions how to get this done?

Just curious:
Considering the nominal voltages are 440V and 220V, is this 50HZ?

ice
 

Sahib

Senior Member
Location
India
There really aren't any other choices. On a container, sounds like it is temporary. The generator may be the best option, on less fuel is a problem. If it is permanent, then you have various choices of phase converter options. With a hermetic compressor motor, those choices are further limited to either a Rotary Phase Converter (RPC), or an electronic phase converter, like a VFD or a "Phase Perfect" unit. Stay away from the Static Phase Converters because they basically just "trick" the motor into starting with single phase, but de-rate the motor capacity when running. That's OK for some loads, but will smoke your compressor on a refrigeration compressor.
I think using capacitors for three phase motor on single phase possible and has no motor derating problem. But cost may be the deterrent.
 
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GoldDigger

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I think using capacitors for three phase motor on single phase possible and has no motor derating problem. But cost may be the deterrent.
There is no combination of fixed value capacitors that can do what you suggest over both motor starting and various fractions of full load.
At best a very lightly loaded motor with zero load at startup could serve as its own rotary phase converter, but full load capacity will unavoidably reduced.
A VFD will be the most versatile option, while a solid state active three phase supply (essentially a fixed frequency VFD) may cost less or more than a VFD depending on the size involved.
A rotary phase converter may be the cheapest solution if you already have a unused three phase motor sized to at least three times the FLA of the motor to be powered.
 
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Sahib

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Consider a three phase supply with one phase lost. If a suitable size capacitor is connected between the lost phase line and a healthy phase, rated current of the motor may flow in each line with a phase shift from the capacitor, thereby making the motor works as a single phase motor and it may develop rated output as rated current flows in each of its winding. Of course to suit this to the OP, a transformer is required to step up 220V to 440V.
 

ActionDave

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Consider a three phase supply with one phase lost. If a suitable size capacitor is connected between the lost phase line and a healthy phase, rated current of the motor may flow in each line with a phase shift from the capacitor, thereby making the motor works as a single phase motor and it may develop rated output as rated current flows in each of its winding.
For sure. To do that though you would have to be super strong, super smart, super fast, and have a capacitor that can't be found. Who among those born on planet earth can do all of this? Not many.

Of course to suit this to the OP, a transformer is required to step up 220V to 440V.
Those are not as hard to find.
 

Sahib

Senior Member
Location
India
Just stop, really just stop.

This refrigeration compressor is not going to start with single phase.
Yes. You are correct. This refrigeration compressor is not going to start with 220V single phase. It is rated for 440V (See my post#11 to clear your confusion.)
 

kwired

Electron manager
Location
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With the static phase converter, a much higher value capacitor is needed to start the motor, you then need to drop the capacitor size once started. It is difficult to get balanced current on all three phases of the motor, and should you accomplish that, it only works on a motor with a constant load applied. Change the load and the capacitor needs changed to balance it again. Static converters work best when motor is oversized for the driven load, and when intentionally putting a three phase motor in a single phase application they do intentionally oversize the motor for this reason.
 

Sahib

Senior Member
Location
India
The only reason static convertor motor oversized is one winding unused.That is not the case for suggestion in post#11.
 

kwired

Electron manager
Location
NE Nebraska
The only reason static convertor motor oversized is one winding unused.That is not the case for suggestion in post#11.
:?What you described in post 11 is exactly how a static converter works, along with a second starting capacitor and control method to switch the start capacitor in/out of the circuit.

I have yet to see one that allows for balanced output current across the three leads to the motor.

Most recent one I dealt with had a motor rated about 25 amps, one line would draw up to 40 amps when at highest load level, and the other two lines would vary depending on how much capacitor was connected but always would sum up to the other line because ultimately what ever comes in one line may split two ways but all has to leave the other line on a single phase supply. I could connect capacitors to get decent current balance but that was when motor was lightly loaded. Static converter only works well with constant load applications, and typically requires derating the motor AFAIK.
 

Sahib

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Location
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:?What you described in post 11 is exactly how a static converter works, along with a second starting capacitor and control method to switch the start capacitor in/out of the circuit.I have yet to see one that allows for balanced output current across the three leads to the motor.Most recent one I dealt with had a motor rated about 25 amps, one line would draw up to 40 amps when at highest load level, and the other two lines would vary depending on how much capacitor was connected but always would sum up to the other line because ultimately what ever comes in one line may split two ways but all has to leave the other line on a single phase supply. I could connect capacitors to get decent current balance but that was when motor was lightly loaded. Static converter only works well with constant load applications, and typically requires derating the motor AFAIK.
Let the voltage be 440V as in OP case. What size capacitor for 25A?
 

GoldDigger

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Keep in mind that starting with just a single phase, the best you can do with a capacitor/inductor combination for starting is 90 degree phase shift, not 120.
The near 120 degree phase shift you get from a rotary convertor (auto motor generator) is because of the 120 rotational phase shift of the windings. The run capacitors, if any, simply helps to stabilize that voltage by providing a balanced voltage divider from the two real phase lines to the derived phase line.
 
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