Convert 1ph to 3phase for motor

[BlinkingLeds]

Hello to everyone , I have a 3phase pump for water which is 150 feet underground and i want to be able to power it from my little 1phase generator in an event of a fire and a blackout (this has happened before). I've got a PS21243-AB DATASHEET and i wonder if i can do that with this. I don't know if i can supply 3phase square wave AC to a motor that normally has 3phase sine wave AC. Is there a problem with that?.
although i think i can make it work (but not so sure about it ), any suggestions on how to wire up this chip correctly will be greatly appriciated.
Thanks in advance.

 

[DuctDuck]

Sorry to dissappoint you, your IC selection is wrong for the application. From the datasheet link, fig. 2, the AC input has to be 3 phase (but its rectified). That is not a neutral-grn-live input connection.

http://en.wikipedia.org/wiki/Scott-T_transformer

 

[BlinkingLeds]

Doesn't this mean that it needs DC?

 

[DuctDuck]

Your problem is very old! Desire for a powerful and versatile AC source to drive mechanical systems. Whew, better let off some steam during a bike ride.

Waste some bandwidth and read about 3phase transformers and 3 phase loading, etc.

There is no magical IC to interleave power for your motor.

 

[BlinkingLeds]

This IC has 3 IGBT half bridges It means that if i supply DC to it it will make 3phase square wave AC doesn't it?

IT states at the beginning "INTEGRATED POWER FUNCTIONS
600V/30A low-loss CSTBTTM inverter bridge for three
phase DC-to-AC power conversion"

Isn't that exactly what i need?

 

[DuctDuck]

Yup, 3 phase DC is what you need! Please refer to page 5/10 of your pdf link.

Demanding those power levels from DC rectified single phase doesn't seem realistic.

 

[BlinkingLeds]

what power levels? i only need 2kw max so i get one phase and get it through a rectifier bridge so now i have dc and i give it to the IC. The IC can now supply 3phase square ac

 

[BlinkingLeds]

This is a DATASHEET of another IC i have

 

[DuctDuck]

okay, fine...you have square wave 3 phase and you can point and laugh; not the rest of the population.

A sqaure wave voltage pulse equates to a current pulse as well, implying larger than normal current draw and heat. Is this good for the motor's windings? It should be easy enough to calculate the differences in sine wave from square wave current waveforms. Motor failure is an eventuallity but predicted when?

 

[BlinkingLeds]

Now that's exactly what i asked in my first post "Is square wave ac instead of sine wave good for the motor?" I really don't have an idea and i don't have a small 3phase motor to try it.
Actually the second IC is from my air conditioner. I've seen the circuit it takes on phase runs it trough a rectifier bridge and gives DC to the IC. The IC produces 3phase AC (not 50hz but whatever frequency the uC gives to it , and that's how the compressor run at different speeds)

 

[BlinkingLeds]

If the difference in the current draw is not very big i think the motor can withstand that because it's under 150 feet of 70 Fahrenheit water.
If the current difference is big i can always reduce the voltage so it will not draw as many amps right?

 

[DuctDuck]

hmm, fascinating.

 

[duke37]

You should not reduce the voltage on an AC motor, if you do, and the torque generated is not sufficient then there will be more slip and more current taken. Motor goes pop?

 

[BlinkingLeds]

is there any other way to reduce it's current?
and what do you mean "Motor goes pop"?
Thanks.

 

[BlinkingLeds]

This ic is going to work right?

 

[duke37]

I bought a book, "Alternating current machines" by Say for a few pence and found it interesting reading. This is the extent of my knowledge.

As I understand it, the current is determined by the required torque and variable speed drives vary frequency and voltage. I would stick with the proper voltage and frequency.

By pop I meant the sound made when the wires fuse.

There are others on the forum who have more knowledge than me in electrical engineering, perhaps they will chime in.

 

[(*steve*)]

Often changes in frequency need to be accompanied by changes in voltage to maintain the same torque (for induction motors??).

But like duke37, this is not an area of expertise. I am just parroting what I have heard/read.

 

[BlinkingLeds]

But if it's pumping water do i need that much torque?

 

[duke37]

Have you tried pumping water by hand? You need a lot of power.

The torque may be low if the head is low but impeller type pumps seem to be designed to give a reasonable efficiency with high pressure, low flow and low pressure high flow output so the torque will not vary much.

If you wish to alter the frequency, you can get drives which are fitted to lathes, also my brother has a vacuum pump for milking which has a variable drive so that it only pumps what is necessary so saves power. This will be a vane constant displacement pump.

An impeller works by flinging the water to the outside, if the speed is too low, the pressure will be too low and there will be no flow.

 

[BlinkingLeds]

Have you tried pumping water by hand? You need a lot of power.

The torque may be low if the head is low but impeller type pumps seem to be designed to give a reasonable efficiency with high pressure, low flow and low pressure high flow output so the torque will not vary much.

If you wish to alter the frequency, you can get drives which are fitted to lathes, also my brother has a vacuum pump for milking which has a variable drive so that it only pumps what is necessary so saves power. This will be a vane constant displacement pump.

An impeller works by flinging the water to the outside, if the speed is too low, the pressure will be too low and there will be no flow.

Can't i alter the frequency with the IC i already have?

Those variable frequency drives are costly

The present setup has a pressostat so that the pump works for 1minute then it stops for 2minutes utill the pressure drops and it turns on again
i read someweare that turning on and off repeatedly is not the best thing that could happen to a motor so i was counting on that ic to provide variable frequency as the output frequency of that IC depeands on the iput frequency which i can easily regulate