Electric power guys....waveforms...

[mrvette]

I have a buddy with electrical problems, appliances failing right left center....4 of them in the last month....

I put my old Techtronix lab scope on his lines.....

the wave form is symetrical on both phases, looks the same, except the obvious polarity reversal.....

NOW, I have seen some sloppy looking waveforms and the zero crossing on this one was clean, trick is...the peaks of the waveforms are almost flat topped, as if someone took a hammer and pounded on top of the sand pile, there is still a rounded tip, but it's compresed from being a sine wave, and has a little notch on leading and lagging edge this is true for both phases and both polarities....

those little notches CAN cause harmonics in the line and upset electronics??
I would imagine so, but yet his APPLIANCES are failing, not the TV/Stereo....

the range is a 6 y/o Whirlpoole electric black glass top and it's the oven element not working now....it's good, cal rod checked out 22 ohms....several times in both directions I called the parts house, a new oven controller is 400 bux, for a circuit panel like a disc drive....

modern appliances are built for shit.....

but what gives about the waveform???

:crutches:

 

[turtlevette]

I have a buddy with electrical problems, appliances failing right left center....4 of them in the last month....

I put my old Techtronix lab scope on his lines.....

the wave form is symetrical on both phases, looks the same, except the obvious polarity reversal.....

NOW, I have seen some sloppy looking waveforms and the zero crossing on this one was clean, trick is...the peaks of the waveforms are almost flat topped, as if someone took a hammer and pounded on top of the sand pile, there is still a rounded tip, but it's compresed from being a sine wave, and has a little notch on leading and lagging edge this is true for both phases and both polarities....

those little notches CAN cause harmonics in the line and upset electronics??
I would imagine so, but yet his APPLIANCES are failing, not the TV/Stereo....

the range is a 6 y/o Whirlpoole electric black glass top and it's the oven element not working now....it's good, cal rod checked out 22 ohms....several times in both directions I called the parts house, a new oven controller is 400 bux, for a circuit panel like a disc drive....

modern appliances are built for shit.....

but what gives about the waveform???

:crutches:

Where did you measure?. Sounds like the characteristics of a switching power supply or some other non linear load.

Did you see any spikes? That's what causes problems. Overvoltages normally occur when a load is switched on. If he has a poor ground big loads switching on on one leg will case the other leg to overvoltage. Does you scope have capture? Set it at 140v trigger and start turning things on and off. Watch for a trigger. Then go to the other leg and do the same.

 

[mrvette]

I have a buddy with electrical problems, appliances failing right left center....4 of them in the last month....

I put my old Techtronix lab scope on his lines.....

the wave form is symetrical on both phases, looks the same, except the obvious polarity reversal.....

NOW, I have seen some sloppy looking waveforms and the zero crossing on this one was clean, trick is...the peaks of the waveforms are almost flat topped, as if someone took a hammer and pounded on top of the sand pile, there is still a rounded tip, but it's compresed from being a sine wave, and has a little notch on leading and lagging edge this is true for both phases and both polarities....

those little notches CAN cause harmonics in the line and upset electronics??
I would imagine so, but yet his APPLIANCES are failing, not the TV/Stereo....

the range is a 6 y/o Whirlpoole electric black glass top and it's the oven element not working now....it's good, cal rod checked out 22 ohms....several times in both directions I called the parts house, a new oven controller is 400 bux, for a circuit panel like a disc drive....

modern appliances are built for shit.....

but what gives about the waveform???

:crutches:

Where did you measure?. Sounds like the characteristics of a switching power supply or some other non linear load.

Did you see any spikes? That's what causes problems. Overvoltages normally occur when a load is switched on. If he has a poor ground big loads switching on on one leg will case the other leg to overvoltage. Does you scope have capture? Set it at 140v trigger and start turning things on and off. Watch for a trigger. Then go to the other leg and do the same.

No spikes that I witnessed, he across the river from me, so 15+ miles one way....the counter top/popup toaster melting looked like shitty plastic to me, but it was on the end of the unit, sagged and melted, not really burnt...rest of the unit looked like it was 2 months old, which it is....

no capture, this scope is a old Tek 453 from the early 70's yet....40 years old...:crutches: but for what it is, the damn thing still as accurate as day it was born...go figger...:bonkers::loveletter:

now here is something I never seen before, he is in a row house type thing, each individually owned, and so the main building feed is underground to the meter packs, and then under the slab the length of the building to pop up in the garages and the panels....now I never seen a thinner green taped ground wire going off to the neutral/ground bus bar it was twist capped with some 12 ga wires, making about a ~1/4 inch bundle then up around the box and under a bunch of screws nice and neat, while the power neutral goes to another bux LARGE screw connect, and the two phases go to the breaker as per normal, feeding the phase bus bars as per normal...Sq D panel QO not Homeline....

but it beats the snot out of me how a generator or power dist. network can compress the peaks of sine waves and so it so symetrically....I don't make a habit of scoping power waves, can't recall the last time I did it, been a LONG time, and yes, I would think it was coming from the 1200 watt inverter in the camper....still can't figger it....

 

[DC3]

Could be an undersized neutral. I'd get an electrician to check all the wiring for issues. Also, call the power company and ask if they can connect a "disturbance analyzer" to his house. This is a power quality monitor that can capture waveform snapshots when power anomalies happen. These snapshots can be compared to known signatures to see if something is amiss.

 

[68/70Vette]

If the sine waves are being topped out, they are then starting to approximate square waves. The RMS voltage of the topped out sine waves will be higher than the RMS voltage of sine waves. For appliances that have AC/DC converters, such as TVs, computers, etc. the topped out sine waves probably have no effect. For ohmic power users, such as heaters, and also possibly motors, the increase in RMS voltage could be stressful. (The RMS voltage of a sine wave is 0.714 of the peak voltage. The RMS voltage of a square wave is 1.00 of the peak voltage.)

Anyhow, the bottom line is that your power plant shouldn't be sending you topped out sine waves. No way. (And as you said, a topped out sine wave would have a lot of harmonics, but these are potentially dangerous to AC/DC converters. For ohmic loads and motors, the harmonics shouldn't be an issue. IMO)

Neighbors having problems?
..................

I used to work at an overseas military base. The commercial voltage, 240 vAC, would sometimes to surge to to 260 vAC and upwards. There were also transients. These occurrences would wipe out a lot of consumer electronics. The US government monitored the line voltages. Whenever a power surge occurred and military people had home electronics to fail, the US government would pay for new. Not so for people like me.

 

[big2bird]

If it was a spike, the TV/Stereo would take the hit first.
Oven elements are resistive loads, and pretty durable.
Finding clipping on the waveform is indicative of the power supply topping out.
I would scope it at the service, and see if it's there as well.

 

[turtlevette]

another thought. see what you get for a waveform at your house.

If its clipped again you have a POS scope or bad probe.

Fancy control modules for appliances of all types have about a 3-6 year life. I really doubt there is anything wrong with their power.

 

[mrvette]

another thought. see what you get for a waveform at your house.

If its clipped again you have a POS scope or bad probe.

Fancy control modules for appliances of all types have about a 3-6 year life. I really doubt there is anything wrong with their power.

:smash::fishing: heheheh...I just did, and guess what?? still slightly clipped, but the leading/lagging edge notch is gone, and there is irregularity in the crossover notch scoped 2 outlets, one a bathroom GFI the other a kitchen run real close to the breaker box...same thing

at HIS house there was a very normal looking Zero crossover sine wave....

I have had NO electrical issues here at all, except the lightening strikes knocking everything in the weeds.....

so go figger...it's not the scope or probe, BTDT over the decades...

 

[turtlevette]

[
so go figger...it's not the scope or probe, BTDT over the decades...

not the SCOPE? What then a .gov conspiracy?

 

[mrvette]

[
so go figger...it's not the scope or probe, BTDT over the decades...

not the SCOPE? What then a .gov conspiracy?

NO, a topped out sine wave, I didn't go expecting to take pix of the damn thing,

makes me wonder if the pole/power dist/breakdown plants are not being run into saturation on the cores along the way somewhere....

I know about voltage stabilizing transformers and saturated cores from very OLD tyme Zenith TV sets jeez....in the 70's yet....the output was pretty severely limited, and looked cleaner than this shit, as I RECALL....

only been 40 years....

:crutches:

 

[turtlevette]

[makes me wonder if the pole/power dist/breakdown plants are not being run into saturation on the cores along the way somewhere....

:crutches:

maybe it's that damn nuclear plant with no grounding system.

 

[mrvette]

[makes me wonder if the pole/power dist/breakdown plants are not being run into saturation on the cores along the way somewhere....

:crutches:

maybe it's that damn nuclear plant with no grounding system.

hahahaha, From north carolina??, doubtful......

I know you don't believe me on that one, all I know is what the guy told me on the phone......then after my silence, he sez 'hello' and I reply YGTBFKM without the F.....

:rofl::rofl:

so they drilled a hole through the earth to China, told the Chinese, please don't touch this nut/rod, stuck a 0000000000 ga wire on it at their end, and called it a day.....:rofl:

 

[DC3]

makes me wonder if the pole/power dist/breakdown plants are not being run into saturation on the cores along the way somewhere....

The transformer serving his house could be overloaded as could the substation transformer serving the neighborhood. Easy to do. Especially in older neighborhoods where houses use to consume a lot less power than they now do because of folks adding AC that never had it before and all the new electric and electronic gadgets. I'd contact the power company and see if they will troubleshoot the problem. Ask them to make sure the transformer(s) and service wire to the house are sized properly.

DC