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hilo90mhz

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Joined: 29/12/2018
Location: United States
Posts: 1

Posted: 12:34pm 03 Jan 2019

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Hi everyone! Just getting to know the place and like the projects I'm seeming here. People actually building functional stuff!

The dump load controller is something I have been designing for about a month now.

Will use a large 300-600A(not sure which yet) IGBT fed from a 250A three phase bridge rectifier.

Resistor for now will be a 10kw cartridge heater type that goes into an air duct for central heating. But I will mount it to outside wall of the power shed - it may need fan cooling I am not sure yet. I am hoping if I only use a 10KW heater at 5KW it will not need a blower for open air operation.

The example power source is a hydro electric generator consisting a 11kw three phase brushless field coil excited type hooked to a turgo wheel. Real power output varies between 4kw-10kw based on water level. I will have the generator windings configured for 240v three phase - but voltage can be reconfigured like most of these standard 6 lead generator heads.

I am planning to drive the field with a fixed current source consisting of a large 150w variable rheostat and fixed redundant 48v power supply. This will make its output voltage/hz dependent on speed and require a constant load hence this dump load controller.

The output of the generator will also be connected to a 240v to 48v three phase iron core transformer that is already aquired. This is going to be rectified and fed straight into the 48v battery bank.

Since this is just going through a transformer to be rectified to DC the HZ does not have to stay at a constant 60 like direct AC hydro systems. So I expect anything from 45-80hz to be fine.

The pwm controller will use the 48v battery bank voltage as one of it's inputs. The other main one will be the HV DC buss voltage created by the HV 3 phase rectifier.

I am planning to do the entire control loop on an ATSAMD51G19A programmed in arduino - starting with adafruit itsybitsy m4 dev board but will go to the direct chip on board eventually.

Currently planning to use two INA226 current shunt and voltage monitors for voltage / current sensing. One on the HV side and one on the LV side, with Ti i2c isolators to keep the logic stuff separate from any power electronics. Ti has an app note about using the INA226 with a voltage divider to sense a 400V DC solar buss.
http://www.ti.com/tool/tida-00528?jktype=design

- I will post a draft schematic soon I know it's hard to visualize everything without a diagram.

Edited by hilo90mhz 2019-01-05

Off grid electronics
www.hilo90mhz.com

Revlac

Guru

Joined: 31/12/2016
Location: Australia
Posts: 1026

Posted: 09:44am 09 Jan 2019

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This is going to be a powerful setup.
Is there a quick easy way to cut the water flow to the hydro in case something gets out of hand?

Finding the sweet spot on the variable rheostat may take a bit of time to find, until everything else has settled down on the pwm charge control side.

I will understand a bit more once you have a diagram/photos, would be great.

Cheers Aaron
Off The Grid

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