Hi guys,
no doubt this will be a very easy question for everyone here but electronics is far from my strongest subject!
For my final year uni project I am working on an eddy current engine dynamometer. For those that don't know it is basically a rotor which spins with coils around it, when current is run through the coils eddy currents are produced in the rotor and applies a braking torque through ohmic heating.
For my calculations of how much current is required etc, I need some of the electrical characteristics of the coils, these being the resistance and the inductance.
My supervisor suggested using an oscilloscope to test these where the basic method would be:
1. Ensure both switches are in the open position, then create a series circuit connecting the battery, switch A, precision 1ohm resistor and dynamometer coil
2. Connect Switch B and 1Kohm resistor across the dynamometer coil
3. Connect the oscilloscope across the precision resistor
4. Turn on the oscilloscope and adjust the settings to read the correct scale
5. Adjust the settings on the Oscilloscope to store the waveform
6. Start the oscilloscope recording
7. Close switch A and record the data into the oscilloscope, noting the filename on the lab test sheet
8. Discharge the energy in the coils (close switch B)
9. Open switch A
10. Fit an exponential curve to the data to obtain the RL time constant and the resistance of the circuit
11. Subtract the effect of the 1Ohm precision resistor to obtain achieve an estimate of the properties of the windings.
As I understand it, I am calculating the RL time constant using this method from the time is takes the coils to discharge and I use a laplace transform table to get to the values I need? I have never touched on this theory before though so any help at all would be greatly appreciated!
no doubt this will be a very easy question for everyone here but electronics is far from my strongest subject!
For my final year uni project I am working on an eddy current engine dynamometer. For those that don't know it is basically a rotor which spins with coils around it, when current is run through the coils eddy currents are produced in the rotor and applies a braking torque through ohmic heating.
For my calculations of how much current is required etc, I need some of the electrical characteristics of the coils, these being the resistance and the inductance.
My supervisor suggested using an oscilloscope to test these where the basic method would be:
1. Ensure both switches are in the open position, then create a series circuit connecting the battery, switch A, precision 1ohm resistor and dynamometer coil
2. Connect Switch B and 1Kohm resistor across the dynamometer coil
3. Connect the oscilloscope across the precision resistor
4. Turn on the oscilloscope and adjust the settings to read the correct scale
5. Adjust the settings on the Oscilloscope to store the waveform
6. Start the oscilloscope recording
7. Close switch A and record the data into the oscilloscope, noting the filename on the lab test sheet
8. Discharge the energy in the coils (close switch B)
9. Open switch A
10. Fit an exponential curve to the data to obtain the RL time constant and the resistance of the circuit
11. Subtract the effect of the 1Ohm precision resistor to obtain achieve an estimate of the properties of the windings.
As I understand it, I am calculating the RL time constant using this method from the time is takes the coils to discharge and I use a laplace transform table to get to the values I need? I have never touched on this theory before though so any help at all would be greatly appreciated!