Commit 347d9df1 authored by avassil's avatar avassil

Review: calculate power rating of the component, small arangements to the PCB,

parent cae01622
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......@@ -4,7 +4,7 @@ A set of AC and DC, voltage and current , sensor components provisioned for inte
In this repository all the design issues are addressed and reusable schematic and pcb design components are developed.
The datalogger is provisioned to be used at small wind turbine systems of nominal power 600W, 1kW and 1.8kW and with a battery storage of 24V and 48V. The sensor modules are
sized based on these specifications and the design restrictions.The
sized based on these specifications and the design restrictions.The
# Electric Measurement isolation
......@@ -20,13 +20,39 @@ Digital side isolation is mainly used for medium resolution and medium sampling
The most common sensor technologies today are the
* current transformer (CT) and the
* low resistance current shunt.
* Hall Effect transducers
* Rogowski coil
# Circuit Design
## AC Current
For the measurement of the 3ph AC currents the use of Current Transformers (CT) is decided.
### CT Burden Calculations
Burden resistance affects the accuracy of the CT, as the burden resistance increases, the magnetic impedance draws more current, which results in measurement error and nonlinearity for the entire range.
Let say that:
```math
I_{p} = Primary current
I_{s} = Secondary current
N = Turn ratio
Z_{m} = Core impendance calculated at the Secondary
Z_{s} = Secondary source impendance
R_{B} = Burden resistanse
Error calculation:
V_{measur} = I_{s} \cdot (\frac {(Z_{m} \cdot (Z_{s} + R_{B}))} {Z_{m} + (Z_{s} + R_{B})} )
V_{real} = I_{m} \cdot Z_{m}
I_{B} = I_{s} - I{m}
```
* CST-1030
I_{nominal} = 30A
N = 1:1000
Nonlinear zone = 45-65Hz
```math
R_{B} = \frac {200mV \cdot N} {I_{P}} = 6.67 ohm
```
## AC Voltage
In such applications, usually a resistor divider (R1 and R2) is used to match the relatively small input voltage range of the ADC. A differential isolation amplifier is used at the analog side.
......
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