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DC through a step up transformer
- Thread starter Irishman89
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gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110625-1257 EDT
realolman:
Some definitions:
A repetitive signal is one that has a repeating waveform that is the same from - infinity to +infinity. This repeating waveform has a period and that defines the lowest frequency component, the fundamental. All other other frequency components are harmonics of the fundamental, meaning integral multiples of the fundamental.
There is a DC component to this waveform that can be anything from -infinity thru 0 to +infinity. The DC component is of constant amplitude that never changes.
If the DC component was 0, then you would certainly call the waveform an AC signal.
If the AC signal was large relative to the DC component this might be classified as an AC signal with a small DC component.
If the AC signal is small compared to the DC component, then consider this as DC with a small AC component, or maybe DC with X % ripple.
If there is no path for a DC signal between primary and secondary of a transformer (infinite leakage resistance from primary to secondary), then there can not be any DC component in the output. After steady-state is achieved the transformer flux will have rebalanced so there is no output DC component.
No DC component exists if the area under the positive half of the waveform equals the area under the negative half. It may be easier to visualize the removal of the DC component with a capacitor than a transformer.
.
realolman:
Some definitions:
A repetitive signal is one that has a repeating waveform that is the same from - infinity to +infinity. This repeating waveform has a period and that defines the lowest frequency component, the fundamental. All other other frequency components are harmonics of the fundamental, meaning integral multiples of the fundamental.
There is a DC component to this waveform that can be anything from -infinity thru 0 to +infinity. The DC component is of constant amplitude that never changes.
If the DC component was 0, then you would certainly call the waveform an AC signal.
If the AC signal was large relative to the DC component this might be classified as an AC signal with a small DC component.
If the AC signal is small compared to the DC component, then consider this as DC with a small AC component, or maybe DC with X % ripple.
If there is no path for a DC signal between primary and secondary of a transformer (infinite leakage resistance from primary to secondary), then there can not be any DC component in the output. After steady-state is achieved the transformer flux will have rebalanced so there is no output DC component.
The shape of the waveform under steady-state conditions has nothing to do with a DC component. No DC component is the same as saying the DC component is 0.By this you are talking about non-sinusoidal AC? ... otherwise why is this not DC?
No DC component exists if the area under the positive half of the waveform equals the area under the negative half. It may be easier to visualize the removal of the DC component with a capacitor than a transformer.
.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110625-1357 EDT
Try these for definitions:
DC --- an absolutely constant signal with no AC component.
AC --- a varying signal with no DC component.
Anything else is DC with an AC component, or DC with an AC component.
.
Try these for definitions:
DC --- an absolutely constant signal with no AC component.
AC --- a varying signal with no DC component.
Anything else is DC with an AC component, or DC with an AC component.
.
110625-1257 EDT
realolman:
Some definitions:
A repetitive signal is one that has a repeating waveform that is the same from - infinity to +infinity. This repeating waveform has a period and that defines the lowest frequency component, the fundamental. All other other frequency components are harmonics of the fundamental, meaning integral multiples of the fundamental.
There is a DC component to this waveform that can be anything from -infinity thru 0 to +infinity. The DC component is of constant amplitude that never changes.
If the DC component was 0, then you would certainly call the waveform an AC signal.
If the AC signal was large relative to the DC component this might be classified as an AC signal with a small DC component.
If the AC signal is small compared to the DC component, then consider this as DC with a small AC component, or maybe DC with X % ripple.
If there is no path for a DC signal between primary and secondary of a transformer (infinite leakage resistance from primary to secondary), then there can not be any DC component in the output. After steady-state is achieved the transformer flux will have rebalanced so there is no output DC component.
The shape of the waveform under steady-state conditions has nothing to do with a DC component. No DC component is the same as saying the DC component is 0.
No DC component exists if the area under the positive half of the waveform equals the area under the negative half. It may be easier to visualize the removal of the DC component with a capacitor than a transformer.
.
If you apply a balanced sq-wave input to a transformer, no DC component,
So what you were talking about is non-sinusoidal AC?:?
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110625-1606 EDT
realolman:
Yes a square wave with no DC component is an AC signal. A sine wave shape has nothing to do with whether a signal is AC or DC. So is the chopped output from a battery an AC signal, but it has a large DC component.
Suppose the car radio power supply has a vibrator (chopper) that produces exactly a 50% duty cycle. If the battery is 6 V, then the peak to peak voltage into 1/2 of the transformer primary is 0 to +6 V, and the DC component is +3 V. On the opposite side of the primary exactly the same signal is applied but exactly 180 degrees out of phase.
The effective AC input to the flux of the transformer is equivalent to a square wave of +/- 6 V to 1/2 of the primary. But the two DC components are the equivalent of + and - 3 volts which subtract to 0 since the DC components are constant independent of time. The result is no unbalanced DC component to unbalance the core flux.
If only 1/2 of the primary had been used, then the transformer would have been less efficient because the DC component would have unbalanced the core flux which would not have an average value of 0.
.
realolman:
Yes a square wave with no DC component is an AC signal. A sine wave shape has nothing to do with whether a signal is AC or DC. So is the chopped output from a battery an AC signal, but it has a large DC component.
Suppose the car radio power supply has a vibrator (chopper) that produces exactly a 50% duty cycle. If the battery is 6 V, then the peak to peak voltage into 1/2 of the transformer primary is 0 to +6 V, and the DC component is +3 V. On the opposite side of the primary exactly the same signal is applied but exactly 180 degrees out of phase.
The effective AC input to the flux of the transformer is equivalent to a square wave of +/- 6 V to 1/2 of the primary. But the two DC components are the equivalent of + and - 3 volts which subtract to 0 since the DC components are constant independent of time. The result is no unbalanced DC component to unbalance the core flux.
If only 1/2 of the primary had been used, then the transformer would have been less efficient because the DC component would have unbalanced the core flux which would not have an average value of 0.
.
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