My name is edris and I am a student. I am doing a project about a windmill. I have to make a controller system for this windmill The first thing I want to know is what is it generating?

So after the 3 phases there is a rectifier and after this I want to measure.

The windmill can generate at average about 50 Volts DC and 10 Amps of current. So this will make a power generated of about P = U * I > 50 * 10 = 500 Watts Right?

Now the problem is I want to measure voltage and current. And there are alot of ways like a voltage divider with a voltage follower with a opamp that creates high impedance and will let little current through. That's for the Voltage.

But then I thought maybey if there is a chip/board that can measure both and calculates this and then sends this data to a i2c line.

Now I found a LTC2946 chip http://www.linear.com/product/LTC2946 I actualy don't understand how to set this up. The problem this chip needs a sense resistor. On that page they have chosen a 0.02 Ohm sense resistor.

So let's do a little math.

So I know the value of the resistor right? >> 0.02 Ohm Say my current is 10 Amps >>

Ohms law = V = I * R right? So my voltage will be 10 * 0.02 = 0.2 Volt or 200 mVolts So can I say then that I need a > 0.2 * 10 = 2 Watt High Power Resistor Is this right?

Say my current will be 15 Amps. That make 15*0.02 = 0.3 Volts This will make > 0.3 * 15 = 4.5 Watss of High Power Resistor right? I don't know if I am doing this right !

If so then the next problem will occur.

How can I measure voltages with this chip? I don't understand.

If you guys know anything, help is appreciated.

Kindly Regards,

Edris

PART 2

Thanx guys for your replys

Now I found something the LTC2947. The last one was LTC2946 and this one needed a external sense resistor. Take the LTC2946, which has a full-scale voltage of approximately 100mV. If the LTC2946 is used to measure a 30A rail, a 3.3 mili Ohm sense resistor is required. This is readily available but will have to dissipate 2.9W of power !!!!.

Now that is alot of disipation of power for a simple measurement. Furthermore the package is not "standard" and therefore expensive.

Then I saw the LTC2947 chip. http://www.linear.com/product/LTC2947

datasheet >> http://cds.linear.com/docs/en/datasheet/2947f.pdf

This chip has a integrated sense resistor of 300µ Ohms. So this is a very efficient chip with high accuracy.

I have looked in the datasheet and found a the section "48V Bidirectional Power, Energy and Charge Monitor with Isolated I2C Interface and High Side Sense"

So I don't think I am gonna use the LTC2946 because of the high power loss.

But the next problem occurs. Does this chip measure votages beyond 48Volts ? Because the windmill can generate higher than that, it depends on the wind.

If not how can I make this work? In which way?

Kindly regards,

Edris

I am doing a project about a windmill. I have to make a controller system for this windmill The first thing I want to know is what is it generating?

So after the 3 phases there is a rectifier and after this I want to measure.

The windmill can generate at average about 50 Volts DC and 10 Amps of current. So this will make a power generated of about P = U * I > 50 * 10 = 500 Watts Right?

Now the problem is I want to measure voltage and current. And there are a lot of ways like a voltage divider with a voltage follower with a opamp that creates high impedance and will let little current through. That's for the Voltage.

But then I thought may be if there is a chip/board that can measure both and calculates this and then sends this data to a i2c line.

Now I found a LTC2946 chip 
I actually don't understand how to set this up. The problem this chip needs a sense resistor. On that page they have chosen a 0.02 Ohm sense resistor.

So let's do a little math.

So I know the value of the resistor right? >> 0.02 Ohm Say my current is 10 Amps >>

Ohms law = V = I * R right? So my voltage will be 10 * 0.02 = 0.2 Volt or 200 mVolts So can I say then that I need a > 0.2 * 10 = 2 Watt High Power Resistor Is this right?

Say my current will be 15 Amps. That make 15*0.02 = 0.3 Volts This will make > 0.3 * 15 = 4.5 Watts of High Power Resistor right? I don't know if I am doing this right !

If so then the next problem will occur.

How can I measure voltages with this chip? I don't understand.

If you guys know anything, help is appreciated.

PART 2

Now I found something the LTC2947. The last one was LTC2946 and this one needed a external sense resistor. Take the LTC2946, which has a full-scale voltage of approximately 100mV. If the LTC2946 is used to measure a 30A rail, a 3.3 mili Ohm sense resistor is required. This is readily available but will have to dissipate 2.9W of power !!!!.

Now that is a lot of dissipation of power for a simple measurement. Furthermore the package is not "standard" and therefore expensive.

Then I saw the LTC2947 chip. Datasheet

This chip has a integrated sense resistor of 300µ Ohms. So this is a very efficient chip with high accuracy.

I have looked in the datasheet and found a the section "48V Bidirectional Power, Energy and Charge Monitor with Isolated I2C Interface and High Side Sense"

So I don't think I am gonna use the LTC2946 because of the high power loss.

But the next problem occurs. Does this chip measure voltages beyond 48Volts ? Because the windmill can generate higher than that, it depends on the wind.

If not how can I make this work? In which way?

My name is edris and I am a student. I am doing a project about a windmill. I have to make a controller system for this windmill The first thing I want to know is what is it generating?

So after the 3 phases there is a rectifier and after this I want to measure.

The windmill can generate at average about 50 Volts DC and 10 Amps of current. So this will make a power generated of about P = U * I > 50 * 10 = 500 Watts Right?

Now the problem is I want to measure voltage and current. And there are alot of ways like a voltage divider with a voltage follower with a opamp that creates high impedance and will let little current through. That's for the Voltage.

But then I thought maybey if there is a chip/board that can measure both and calculates this and then sends this data to a i2c line.

Now I found a LTC2946 chip http://www.linear.com/product/LTC2946 I actualy don't understand how to set this up. The problem this chip needs a sense resistor. On that page they have chosen a 0.02 Ohm sense resistor.

So let's do a little math.

So I know the value of the resistor right? >> 0.02 Ohm Say my current is 10 Amps >>

Ohms law = V = I * R right? So my voltage will be 10 * 0.02 = 0.2 Volt or 200 mVolts So can I say then that I need a > 0.2 * 10 = 2 Watt High Power Resistor Is this right?

Say my current will be 15 Amps. That make 15*0.02 = 0.3 Volts This will make > 0.3 * 15 = 4.5 Watss of High Power Resistor right? I don't know if I am doing this right !

If so then the next problem will occur.

How can I measure voltages with this chip? I don't understand.

If you guys know anything, help is appreciated.

Kindly Regards,

Edris

My name is edris and I am a student. I am doing a project about a windmill. I have to make a controller system for this windmill The first thing I want to know is what is it generating?

So after the 3 phases there is a rectifier and after this I want to measure.

The windmill can generate at average about 50 Volts DC and 10 Amps of current. So this will make a power generated of about P = U * I > 50 * 10 = 500 Watts Right?

Now the problem is I want to measure voltage and current. And there are alot of ways like a voltage divider with a voltage follower with a opamp that creates high impedance and will let little current through. That's for the Voltage.

But then I thought maybey if there is a chip/board that can measure both and calculates this and then sends this data to a i2c line.

Now I found a LTC2946 chip http://www.linear.com/product/LTC2946 I actualy don't understand how to set this up. The problem this chip needs a sense resistor. On that page they have chosen a 0.02 Ohm sense resistor.

So let's do a little math.

So I know the value of the resistor right? >> 0.02 Ohm Say my current is 10 Amps >>

Ohms law = V = I * R right? So my voltage will be 10 * 0.02 = 0.2 Volt or 200 mVolts So can I say then that I need a > 0.2 * 10 = 2 Watt High Power Resistor Is this right?

Say my current will be 15 Amps. That make 15*0.02 = 0.3 Volts This will make > 0.3 * 15 = 4.5 Watss of High Power Resistor right? I don't know if I am doing this right !

If so then the next problem will occur.

How can I measure voltages with this chip? I don't understand.

If you guys know anything, help is appreciated.

Kindly Regards,

Edris

PART 2

Thanx guys for your replys

Now I found something the LTC2947. The last one was LTC2946 and this one needed a external sense resistor. Take the LTC2946, which has a full-scale voltage of approximately 100mV. If the LTC2946 is used to measure a 30A rail, a 3.3 mili Ohm sense resistor is required. This is readily available but will have to dissipate 2.9W of power !!!!.

Now that is alot of disipation of power for a simple measurement. Furthermore the package is not "standard" and therefore expensive.

Then I saw the LTC2947 chip. http://www.linear.com/product/LTC2947

datasheet >> http://cds.linear.com/docs/en/datasheet/2947f.pdf

This chip has a integrated sense resistor of 300µ Ohms. So this is a very efficient chip with high accuracy.

I have looked in the datasheet and found a the section "48V Bidirectional Power, Energy and Charge Monitor with Isolated I2C Interface and High Side Sense"

So I don't think I am gonna use the LTC2946 because of the high power loss.

But the next problem occurs. Does this chip measure votages beyond 48Volts ? Because the windmill can generate higher than that, it depends on the wind.

If not how can I make this work? In which way?

Kindly regards,

Edris