cupoftea
Advanced Member level 5
Hi,
The attached schem and LTspice sim, shows two 40W offline loads.
One represents a 40W SMPS with a 47uF HVDC Post rectifier Bus cap and the peak of its mains input current is
2.5A.
The other represents eg an 40W induction motor load with a sinusoidal
input current of just 240mA peak.
There is clearly a massive difference in their peak mains input current, even though they are both 40W Loads.
Now lets say that each of them is supplied the "mains" by a little portable, off-grid, 40W, 12V to 240VAC, pure sinusoidal inverter.
Such an inverter would have an overcurrent limit. At most, this would be about 240mA + 20%, ie, 288mA.
This is nowhere near enough peak current rating to be able to supply the 2.5A peak that the real mains can supply for the one with the
47uF cap.
As such, the 40W pure sinusoidal inverter will struggle to properly supply the 40W load with the 47uF bus cap.
Also, its current and voltage waveforms will get warped, and not be particularly sinusoidal at all.
It makes you wonder, why anyone would bother to ever use a Pure sinusoidal inverter for such a case?
Why would they? What is the reason for it?
___---___---___---___--___---____
And take this 500W pure sine inverter..
..It says it can supply motors, (so it must mean 50Hz induction motors) but you would have to hope that the particular motor
didnt need much high startup current (like most induction motors do), because this inverter would then just trip out and never start up.
The attached schem and LTspice sim, shows two 40W offline loads.
One represents a 40W SMPS with a 47uF HVDC Post rectifier Bus cap and the peak of its mains input current is
2.5A.
The other represents eg an 40W induction motor load with a sinusoidal
input current of just 240mA peak.
There is clearly a massive difference in their peak mains input current, even though they are both 40W Loads.
Now lets say that each of them is supplied the "mains" by a little portable, off-grid, 40W, 12V to 240VAC, pure sinusoidal inverter.
Such an inverter would have an overcurrent limit. At most, this would be about 240mA + 20%, ie, 288mA.
This is nowhere near enough peak current rating to be able to supply the 2.5A peak that the real mains can supply for the one with the
47uF cap.
As such, the 40W pure sinusoidal inverter will struggle to properly supply the 40W load with the 47uF bus cap.
Also, its current and voltage waveforms will get warped, and not be particularly sinusoidal at all.
It makes you wonder, why anyone would bother to ever use a Pure sinusoidal inverter for such a case?
Why would they? What is the reason for it?
___---___---___---___--___---____
And take this 500W pure sine inverter..
500W - 24V Pure Sine Wave Sunshine Power Inverter
Sunshine Pure Sine Wave Inverters are suited for sensitive electronic equipment, allowing motors to run faster, quieter and cooler, preventing computer crashes, noises & glitches in monitors, TV, game consoles etc. Convert DC power from your battery into AC power enabling use of electrical...
www.sunshinesolar.co.uk
didnt need much high startup current (like most induction motors do), because this inverter would then just trip out and never start up.
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