160307-1556 EST
This forum has real problems with photo attachements, and restore of auto-save..
A redo of my last post.
160307-1215 EST
Dennis thanls.
I made a 1 ohm shunt from multiple carbon comp resistors to reduce the inductance of my current measuring shunt this morning. This reduces some ot the 5 to 10 MHz oscillation I was getting.
Three bulbs were tested for inrush current. The source was 120 V 60 Hz house power. The switch was a 50 A mercury relay. In the past I have switched upwards of 10,000 A for a moment with this relay.
The test results follow:
Red is voltage, and blue is current.
60 W incandescent.
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The peak inrush is about 8 A for one bulb. The Peak to RMS steady-state current ratio is 8/0.5 = 16. Total duration of inrush is about 3 mS. An estimate of I^2*T = 8*8*0.001 = 0.064 A^2*S.
9.5 W CREE (60 W equivalent).
Both plots are exactly the same measurement. The first is at 2 mS/div, and the second at 100 microseconds/div.
The peak inrush is about 5 A for one bulb. Peak to RMS steady-state is 5/0.079 = 63. Peak current occurs at about 100 microseconds, and total duration is about 400 microseconds. An estimate of I^2*T is 5*5*0.0003 = 0.0075 A^2*S.
Thus, the energy per turn on per bulb of the CREE is about 1/10 of that of the incandescent. This inrush only occurs at turn-on, not every cycle. The steady-state wattage ratio between incandescent and CREE is 60/9.5 = 6.3 . Thus, from a steady-state current basis you could use 6.3 CREEs in place of 1 incandescent, and have the same total current. From my estimated I^2*T ratio of 0.064/0.0075 = 8.5 you could use 8.5 CREE bulbs for the same transient energy as the incandescent.
Unless I am way off in my estimates equal total actual wattages should work between CREE and incandescent.
9.5 W Feit with high frequency oscillation near 1 MHz (60 W equivalent)
I have not seen any inrush current on this Feit bulb. The AC voltage before the turn on time is from the capacitive coupling thru the mercury relay to what appears to be a very high impedance FEIT bulb when it is off. This is not a dimmable FEIT.
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