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0joze0

Tue Jan 17 2012, 01:33PM

Registered Member #4346 Joined: Tue Jan 17 2012, 10:16AM
Location: Slovenia
Posts: 9

Hello,

I want to make power line , 300 meters long with wires of 1mm2.
need to transmitt 3000 W.
At input I have 220V/50 Hz, the same I want to have at output.
Need to have as small and light weight as possible transformers-I heard that this could be done with higher frequencys.
I am thinking this:

first convert 220V/50Hz to 220V/how high freq.?
Then convert with transformer to 2000V.. ok? ( what are demands for this transformer?)
at end again transformer from 2000V to 220V , and at end convert high frequency to 50Hz.

Please for your suggestions what is best and easy way to do this.

best regards,
Joze

m4ge123

Tue Jan 17 2012, 02:17PM

Registered Member #4118 Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140

I would say make a ~1kV boost converter out of IGBTs (well 1 IGBT really), then a 310V buck converter at the other end with PWM and a full bridge to convert back to 50Hz AC.

Edit: see

Sulaiman

Tue Jan 17 2012, 06:10PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

You're talking serious investment in cash or prototyping,
(I'd love to see a risk assessment)
a portable generator would probably be cheaper,
or a UPS if only short-term use.
(Many UPSs will not start up dc/ac conversion until after the Mains/Line startup)

Dr. Dark Current

Tue Jan 17 2012, 07:19PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Input: Voltage doubler with 2 diodes and 2 electrolytic caps to make 600 Vdc
Output: Single switch buck converter to make 320 (or so) Vdc, then feed this into the output stage of a switchmode UPS.

klugesmith

Tue Jan 17 2012, 09:06PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

0joze0 wrote ...
I want to make power line , 300 meters long with wires of 1mm2.
need to transmitt 3000 W.
At input I have 220V/50 Hz, the same I want to have at output.

Welcome, Joze.
Here's a strictly valid solution that will be hard to beat, followed a practical suggestion.

Strictly valid:
0. Turn main power switch off.
1. Connect near end of wire pair directly to switched 220V / 50 Hz.
2. Connect far end of wire pair to the low voltage side of a Hammond 182U30 transformer configured as 60V:237 V.

3. Connect high voltage side of transformer to a 750 watt 220 volt load.
4. Switch it on.

The operating line current will be about 13.6 amps.
You are transmitting 3000 watts, losing 75% of it in wire voltage drop, and receiving 750 watts at 55V.
Then boosting it back to 220 VAC with a transformer, to meet your output voltage condition.

The loss of 3.75 watts per meter of conductor won't seriously overload your 1mm^2 wires, unless they are buried or inside a pipe.

More practically, assuming you want to -deliver- 3000 W at 220 V, 50 Hz:
I like the previously stated solutions, particularly running DC through the line.
In a contest for smallest, lightest, or cheapest solution, we need more information:
1. Efficiency requirement. 2. Output harmonic distortion requirement (is modified square wave OK?).

0joze0

Wed Jan 18 2012, 08:48AM

Registered Member #4346 Joined: Tue Jan 17 2012, 10:16AM
Location: Slovenia
Posts: 9

hello and thanks for ideas.

This cable will be power line for driving 6 pcs 300w brushless DC motor ( 48V) , Power LED lights , electronics and power supply for different instruments and sensors.I expect that most of the time, the power consumption will be around 2KW, but not more than 2,5kw. Because of DC voltage demands, I dont think that true or modified sinus is important ask for me ?

Sulaiman

Wed Jan 18 2012, 10:09AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

Maybe you should reword the requirement, 230 Vac 50 Hz to 48 V 50A dc
you can use the 48 Vdc directly for the motors and leds (series or pwm) and
a small dc/230 Vac inverter for misc. instruments,
in which case a hvdc supply down the wires makes more sense with a step-down/buck converter at the receiving end.

Ideally full-wave rectified 3-phase (220/400 Vac) source with very little capacitance (e.g. 10 uF) to reduce the energy available if the long wire line goes short etc.

At the receive end put a diode in series with the line to a large cap bank,
the diode will prevent the cap bank discharging into a line fault.
This would be as safe as possible and not need expensive HRC fuses.

OR

You could send 220 Vac down the line with a ups at the receive end,
most of the time the 220 Vac will be charging/maintaining the ups batteries
ready for short term use (battery capacity),
take the 48 Vdc from the ups batteries directly, not via a 220 Vac/48 Vdc converter.
You could add batteries as required to increase capacity.
The battery capacity must meet the requirements of the motors,
the ups need only be rated for it's ac power output, e.g. 500W for instruments etc.
hence only moderate current in the line.
Virtually no development required, just enough battery capacity.

Steve Conner

Wed Jan 18 2012, 11:09AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I've only seen one thing remotely relevant to this.

This is a long page by a guy in Chile who built his own microhydro system, inlcuding a 2kV transmission line. The transmission line and transformers are described near the bottom.

However, this application, with brushless motors and weight constraints, sounds more like a ROV. The switchmode approach might be better.

Most commercial switchmode power supplies will run happily off 320V DC, so that's an option too. You could maybe crank it up to 400, even 450 and get away with it. (As you increase the input voltage, the current draw will go down automatically.) But for any more, you'd need to modify the SMPS or build your own.

If you can find a big SMPS that made 48V DC from a 400V three phase input, you can feed it 600V DC, and your line current is down to 5A.

0joze0

Wed Jan 18 2012, 11:33AM

Registered Member #4346 Joined: Tue Jan 17 2012, 10:16AM
Location: Slovenia
Posts: 9

Yes, this application is for ROV.
I build one with batteries, but thinking now to have something bigger

0joze0

Thu Jan 19 2012, 07:37AM

Registered Member #4346 Joined: Tue Jan 17 2012, 10:16AM
Location: Slovenia
Posts: 9

maybe someone know for web with good SMPS project described, because I think that it is quite demanding job to build good SMPS

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