@John Sethian posted:In response to Pat’s concern that I may not be measuring the motor current properly, I added a current meter to the leads to one of the motors:
The meter on the right (set at AC) measures the current to the TIU, the meter on the left (set at DC) measures the current to the front motor. To keep things unambiguous, the rear motor is out of the circuit. The meter on the right stabilizes at 0.620 Amps
Note this is a roller test
This is what I got
SMPH One Motor TIU TIU (adjusted)
0 0 .620 0
15 0.57 .844 ,224
20 0.60 .902 .280
25 0.64 .954 .334
30 0.68 .975 .350
35 0.70 1.02 .400
It appears that measuring the current through the TIU is not an accurate way to measure the current through the motor (Thanks Pat) AND at 35 SMPH on rollers I am right at the limit that GRG cited (0.70 x 2 = 1.4 A), so that explains why I had the drop outs when running on the layout.
As I said in a previous post, I have other motors I can try.
I wasn’t trying to be condescending, let me be clear on that, ….John put it in better terms than I did….beings it’s PWM driven, the meter readings ain’t exactly true …is there anyway you can simply disconnect the entire PS3 board set and rev this guy up on a rectifier, or straight DC power?….with both motors parallel?…thats will tell the true story of the amp consumption by both motors,….beings the board set is constantly adding or subtracting voltage ( in an attempt to cruise ) your Fluke can’t take this into account, …Id think your meter is seeing some float, because by your numbers, everything seems honky dory …..I’ve built a lot of large heavy articulated steamers with gigantic Pittmans, and believe me, id be ok with 1.4 amps raw ( that’s pulling a train BTW) ……most big straight frame engines ( 4-8-2s, 4-8-4’s etc, etc,.) with large 9400’s singles I try to get well below an amp before sending them down the road to have electronics added, ….but I do my testing long before the package is added, …..I use my Z4000’s amp meter as a start, but I back it up with my Fluke, cause Z4000’s can be known pathological liars…I can’t say for sure, but my gut is telling me your Kohs with two Pittmans and a dizzying array of drive train might be tugging closer to 2 amps, or even above ….and that might be too much for the PS3 to handle under load…..
Pat
