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help understanding a 220 volt AC single phase motor pattern
help understanding a 220 volt AC single phase motor pattern
I hope this is the correct forum, I normally stay on the Pico automotive forum. I am trying to determine the issue with a 220 volt single phase brushless pump motor. Every 48 hours this pump runs for about a 1/2 hour while a filter is backwashing. At approx. 28 minutes the amperage increases, and the pump is turned off by a protection module. This module monitors the pump current and turns it off if it drops by 20% indicating the well ran dry or increases by 20% indicating the pump is drawing too much current. I am measuring the amperage on the 2 line voltage wires using Pico TA018 amp clamps set on 100mv / amp. These are placed between the main power relay and the pump protection module. I have attached a circuit diagram. While the pump is running normally the wave form is equally above and below the zero line and all the peaks are fairly even. when the pump first turns on, and when it pulls to much current before being turned off, the wave form goes 1.8 v above zero but 3.4 v below zero. I don't understand how an AC circuit could have more amperage below zero than above.
When the pump begins running the peaks in the waveform are fairly even, but when it starts pulling excess current before turning off, the upper part of the wave is fairly even but the lower part of the wave is varying about 850mv in a repeatable pattern. If this was DC fuel pump I would think it had 16 commutator segments and my amp clamp needed to be inverted. The pump mfg was unable to provide any information about the pump construction. I don't think it's heating up because the rpm doesn't change, but I have no idea what's happening to cause the current increase. I have always had trouble completely understanding AC induction motors and would be very appreciative if someone could help me with this.
When the pump begins running the peaks in the waveform are fairly even, but when it starts pulling excess current before turning off, the upper part of the wave is fairly even but the lower part of the wave is varying about 850mv in a repeatable pattern. If this was DC fuel pump I would think it had 16 commutator segments and my amp clamp needed to be inverted. The pump mfg was unable to provide any information about the pump construction. I don't think it's heating up because the rpm doesn't change, but I have no idea what's happening to cause the current increase. I have always had trouble completely understanding AC induction motors and would be very appreciative if someone could help me with this.
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Re: help understanding a 220 volt AC single phase motor pattern
Looks like your start capacitor is turned back on after about 13 min running.
The currents during the tripping are exactly the same as the startup currents.
So I suspect the relais that connects the startup capacitor to the 3th phase.
Benno
The currents during the tripping are exactly the same as the startup currents.
So I suspect the relais that connects the startup capacitor to the 3th phase.
Benno
Re: help understanding a 220 volt AC single phase motor pattern
Thanks, I noticed the amperage drops a little before the final amperage that shuts the pump off. That makes me think the protection module is causing the issue. Now I need to determine if the well was starting to run dry or if the module is defective. What if anything is indicated by the waveform being further below zero than above, and the large variance in size of the peaks. If this was a DC brushed motor I would suspect commutator wear, but I don't know what that indicates in a brushless motor.