Transient  Waveforms
The following pictures show the transient current waveforms for some typical high current appliances.

These waveforms can be downloaded and examined in detail with ArcView.

All of these waveforms were digitized with 12 bit resolution at a rate of 520 microseconds per sample (32 samples per cycle at 60Hz ).


1.   A collection of incandescent lamps with a total power of 1 KW. The power is turned on at a voltage phase angle of 30 degrees. The peak of the initial transient is 7 times the steady-state peak current.

file: 1KW_30D

2.   The same collection of lamps turning on when the voltage phase angle is 60 degrees.

file: 1KW_60D

3.   The 1 KW lamp load being controlled with a dimmer set for maximum power.

file: 1KW_100%

4.   The 1 KW lamp load being controlled with a dimmer set for 75% of maximum.

file: 1KW_75%

5.   Incandescent lamps being turned on with a knife switch. Note the switch bounce.

file: LAMP15_D

6.   A light bulb being screwed into the socket with the power switch on.

500 msec/div

file: LIGHT3


7.   A loose wire at one terminal of a light bulb.

200 msec/div

file: LIGHT4


8.   Computer power supply. 1.7 amp peak, 0.4 amp rms

file: COMPUTR1

9.   Start-up transient of a 1 HP air compressor. The initial high current portion of the waveform lasts longer when the current to the compressor is limited by a long extension cord.

50 msec/div

file: 1HP_AIR


10.   The transient due to a shop vacuum with a varying load.

500 msec/div

file: SHOPVAC1


11.   100 Amp arcing generated by the 'guillotine' test appartus.

file: GUILL_11

12.   Arcing generated by a loose wire at a screw terminal.

file: ARC13

13.   Arcing generated by a loose wire. Note the high frequencies in this waveform.

file: ARC2

14.   Arcing current between two carbon rods.

file: ARCROD

15.   The resistance of a 100W incandescent lamp was reduced about 15 percent after it was dropped one time onto a hard surface using the lamp burnout test fixture described in UL1699 (test specification for arc-fault circuit interrupters).   The lamp did not burn out this time.

Horiz: 10 msec/div
Vert : 0.5 A/div

file: LMPDROP1

16.   A 100W incandescent lamp burned out after being dropped a second time. Note the 2.6X current surge during the last negative half-cycle followed by the even larger transient during the last positive half-cycle.

Horiz: 10 msec/div
Vert : 1.0 A/div

file: LMPBURN5

17.   Another view of the same waveform shown in figure 16 above. The peak current of the last transient is approximately 175 Amps. This is characteristic of this type of test.

Horiz: 10 msec/div
Vert : 40 A/div

file: LMPBURN5

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    Updated: 2-14-05