100 AMP Shunt

[Shadow]

 I'm gonna try my luck at hooking up another Digital amp meter(Gauge) to my wind turbine. I understand I can just build one with copper strap?.. How do I know Whats 100 amp? What resistance should it be?.. Thanks

[wooferhound]

This will help you . . .

http://www.uoguelph.ca/~antoon/gadgets/shunts/shunts.html

[Opera House]

Most high current shunts use multiple parallel sheets of metal.  Remember that this is basically a resistor and resistors are supposed to heat up.  Problem is that as the metal heats up, its resistance increases.  Designing one as a big heat sink with a lot of surface area will help.  I have a torroid transformer that I wound about 9 turns of #12 wire through.  This will give me about 35A at about 1.5 volts AC open circuit.  This allows me to calculate the low value resistance.

[Nando]

Current shunts are made from a nichrome alloy and for a 100 amps, the resistance value needs to be defined for the meter, usually it is 1 Milliamp meter with about 50 Ohms internal resistance for a 50 millivolts Shunt voltage drop at 100 amps, which makes the SHUNT resistance value R = 0.05 volts / 100 amps = 0.0005 Ohms ( one half milliohm) so You need a very large volume nichrome alloy and special copper blocks to solder metal blades.

Then to calibrate it you need a Very Accurate current source and a very accurate meter then the nichrome metal is grounded to increase the resistance value until the meter shows the fed current.

THEREFORE you do not know how to do it or it would be very difficult and / or expensive to do it -- , because your question in your message.

Regards

Nando

[thunderhead]

Once you have calculated the value you require for your shunt, it is not too hard to assemble an accurate resistor of this value.  The important thing to remember is that resistors are cheap.  Even 10W wirewound resistors cost maybe $0.15 each if you buy bulk.

If you want a 0.01Ω resistor for a 100A shunt, it will dissipate 100W.  (Multiply the resistance by the square of the peak current.)  If you use 10 0.1Ω resistors in parallel, this will give you the required value.  If you use 10W resistors, this will also give you the required power dissipation. (Beware, they will get hot.)

If you want a 0.001Ω resistor for a 100A shunt, it will dissipate 10W.  If you use 100 0.1Ω resistors in parallel, you can use the smallest and cheapest resistors you can buy.  Because of the price mechanics of bulk purchase, they will cost maybe $0.64 for all of them.

The accuracy of the shunt you construct will be the same as the accuracy of the chosen resistors, provided they are all the same.  Nowadays 1% tolerance resistors are nothing special.

The biggest problem is the effort of soldering them all up.

[hotwired]

Have some factory made dc shunts what do you need

[Charlane]

A 40 amp would work for me......

Charlane