[Mr V]

Originally Posted by Richard Wallace

Good idea, Russ. I will try that tonight and report results. My team has three types of compressors on hand so I'll attempt to measure starting surge current for each.

-------edit after testing--------

We tested three compressors, using an oscilloscope and current probe to measure (1) initial peak surge current, (2) average current draw during charging, and (3) time to full charge. The test system capacity was 48 cubic inch (3x Clippard AVT 32-16). In each case the duration of the initial surge current was ~0.05 second, rising to its peak in about 0.005 second and decaying exponentially to steady value after that. I have attached a typical oscilloscope plot of the compressor current, 50 seconds full horizontal scale and +/- 40 Ampere full vertical scale. This plot is for the Thomas compressor; other plots are similar in form but differ in their initial peak surge, average current draw, and time to full charge as summarized below.

Viair 90C: initial peak surge 18 Ampere, average current draw during charging 12 Ampere, time to full charge 40 seconds.

Thomas 405ADC38/12: initial peak surge 32 Ampere, average current draw during charging 10 Ampere, time to full charge 36 seconds.

Viair 250C-IG: initial peak surge 40 Ampere, average current draw during charging 9 Ampere, time to full charge 33 seconds.

By time to full charge do you mean starting at 0 psi? The original question on start up current was asking what it was with 100psi already in the tank. Personallly I'd like to see the start up current and time to fill using the on-off range of the legal pressure switch. Time to fill from 0psi and the start up current at that pressure is less critical since you can fill before the match starts and should only occur once per match while the 85-115psi event can potentially happen multiple times in a match. If the fuse were to blow before a match that could easily be corrected before going on the field.