One might think that a man holding the job titles that I have in the past (Field Service - motor controls, et. al.), should be an "expert" on all things motor, but that isn't the case. I'm single phase impaired. Every motor I have ever dealt with in a professional capacity was 3phase or DC, or stepper, or anything-else-but-single-phase. When a single phase motor problem finds me, it always makes me feel stupid. Today's culprit is in my very own attic. Sounded like someone was stumbling around drunk up there.
Here's what my HVAC fan is doing (video):
https://drive.google.com/file/d/0B3Jz02jC_rNgaGtvSkh4Tk4xTkU/view?usp=sharing
Here is a folder of related photos, including wiring diagram:
https://drive.google.com/folderview?id=0B3Jz02jC_rNgeEY2NGxVOVFQTWs&usp=sharing
If you can't see the video, it's acting kinda like a 3 phase motor acts with a missing phase. Lots of ugly humming; makes 1 rev, stops, makes 1 rev, stops, ...
The fact that it's acting like a single phased 3 phase motor initially made me suspect the run cap (the component responsible for generating the "3rd phase" of a single phase motor). I took it off and tested it by the means I have here at the house on Christmas Eve (no LCR or ESR meter). It reads 19.9uF by my fluke DMM and I charged it up to 260V with my megger, held a good charge for a long time. Megger checked for shorts to case, none. Cap is not bulged or leaking, and does not get hot while plugged into the powered circuit.
AFAIK the only thing that could be wrong with the cap is high ESR which i can't test for, but I thought that would make the cap overheat, and it isn't, so I started to suspect the motor. The motor turns very freely by hand, no bearing issues; I can spin it by twisting the shaft with 2 fingers, and it stays spinning for a long time after. No electron leaks, meggered the motor too. motor windings read 14, 17, and 20 ohms for (high, med, low). The motor draws 3.8 amps, whether it's running as it should be (I did get it to run for a while by letting it cool down for a couple hours) or whether it's doing the buzz dance in the video above. Unlike a single phased 3 phase motor, I would expect the amp draw to skyrocket but it doesn't.
I tried spinning the fan as fast as I could by hand and then applying power; when the power hits it, it immediately snaps to a stop and starts doing the buzz dance. The motor is getting 238V to the leads and I read 232V across the cap while it's running.
Is this more likely a bad cap or a bad motor?
@#12 BATSIGNAL
Here's what my HVAC fan is doing (video):
https://drive.google.com/file/d/0B3Jz02jC_rNgaGtvSkh4Tk4xTkU/view?usp=sharing
Here is a folder of related photos, including wiring diagram:
https://drive.google.com/folderview?id=0B3Jz02jC_rNgeEY2NGxVOVFQTWs&usp=sharing
If you can't see the video, it's acting kinda like a 3 phase motor acts with a missing phase. Lots of ugly humming; makes 1 rev, stops, makes 1 rev, stops, ...
The fact that it's acting like a single phased 3 phase motor initially made me suspect the run cap (the component responsible for generating the "3rd phase" of a single phase motor). I took it off and tested it by the means I have here at the house on Christmas Eve (no LCR or ESR meter). It reads 19.9uF by my fluke DMM and I charged it up to 260V with my megger, held a good charge for a long time. Megger checked for shorts to case, none. Cap is not bulged or leaking, and does not get hot while plugged into the powered circuit.
AFAIK the only thing that could be wrong with the cap is high ESR which i can't test for, but I thought that would make the cap overheat, and it isn't, so I started to suspect the motor. The motor turns very freely by hand, no bearing issues; I can spin it by twisting the shaft with 2 fingers, and it stays spinning for a long time after. No electron leaks, meggered the motor too. motor windings read 14, 17, and 20 ohms for (high, med, low). The motor draws 3.8 amps, whether it's running as it should be (I did get it to run for a while by letting it cool down for a couple hours) or whether it's doing the buzz dance in the video above. Unlike a single phased 3 phase motor, I would expect the amp draw to skyrocket but it doesn't.
I tried spinning the fan as fast as I could by hand and then applying power; when the power hits it, it immediately snaps to a stop and starts doing the buzz dance. The motor is getting 238V to the leads and I read 232V across the cap while it's running.
Is this more likely a bad cap or a bad motor?
@#12 BATSIGNAL