here is another one: This was on an ungrounded system so its actually not horribly unsafe
In an ungrounded system, the only first fault that will draw current will be line to line. In that case at least one wire in each line pair will have a working fuse.How so not horribly unsafe.
What is up with the green tape?
If it's corner grounded and that wire is on the grounded phase, a fuse in that position would be superfluous, wouldn't it?In an ungrounded system, the only first fault that will draw current will be line to line. In that case at least one wire in each line pair will have a working fuse.
In an ungrounded system, the only first fault that will draw current will be line to line. In that case at least one wire in each line pair will have a working fuse.
Part 2 still needs an answer; what's up with the green tape?
If it's corner grounded and that wire is on the grounded phase, a fuse in that position would be superfluous, wouldn't it?
An obvious violation. The copper pipe pieces are of unequal lengths! And do not fill the clips properly, so poor contact.Found within the last 4-6 weeks. Resi HVAC disco.
Found within the last 4-6 weeks. Resi HVAC disco.
In a related story in the category of "Here, hold my beer"...
This is probably an Urban Legend, but the story goes that some guy had a fuse blow in his car (probably a beat up pickup truck) and he didn't have a spare, so he replaced the fuse with a .22 cal live round. After a while the fuse got hot, with predictable results, resulting in a gunshot wound to the driver's private parts.
In a related story in the category of "Here, hold my beer"...
This is probably an Urban Legend, but the story goes that some guy had a fuse blow in his car (probably a beat up pickup truck) and he didn't have a spare, so he replaced the fuse with a .22 cal live round. After a while the fuse got hot, with predictable results, resulting in a gunshot wound to the driver's private parts.
That's why I made it.........I use things dependent on the photoelectric effect all the time, but they work whether I understand it or not.
Your point is certainly arguable.
Well, if the 1kg mass is already moving at .99 times the speed of light, the acceleration would not be what Newton's laws predict.
A more practical example is the photoelectric effect, in which we find that photons interact as if they have momentum, but no rest mass and have quantized energy which depends on frequency.
But do you have to use either in any practical circumstances?
I use things dependent on the photoelectric effect all the time, but they work whether I understand it or not.
Your point is certainly arguable.
That's why I made it.........
The operation was a success and the patient died.OK
Something a bit different.
From about 20 years ago.
We were commissioning a suite of DC fed DC drives that we'd made. Some of these were quite big, 400kW, and about half were four quadrant - reversible and regenerative modes included.
The supply was from a 24-pulse rectifier producing 700Vdc and rated at about 6,000Adc. The DC bus had a couple of huge capacitor banks comprising hundreds of electrolytic capacitors.
We didn't have the facilities in our works to load test these drives at their full power rating. The current, the volts, but not both at the same time.
But a colleague and I decided that a thermal run at full chat would be a good idea. We devised a test on site. Run one drive motoring and the in regeneration. The DC bus just supplies the losses.Simple, brilliant, ingenious. We rather liked the idea.
We set it up using two DC machines that were part of Ward-Leonard system - kit that we were replacing. OK. We ran it up and left the test running for a couple of hours. All good.
Then we came to stop it. In what sequence? Well obviously stopping the motor powering the test set would remove the power input. Wouldn't it? So that's what I did.
Brain fade hardly describes what happened next. The regen drive kept regenerating into the DC link. With no power being consumed, the regen pumped up the DC link voltage. Beyond the limits of the capacitors.
Capacitors blew up like improvised explosive devices and the carnage seemed to last forever....lit up the substation walls with one blue flash after another.
The implement of electrical destruction was me. myself, and I.
OK
Something a bit different.
From about 20 years ago.
We were commissioning a suite of DC fed DC drives that we'd made. Some of these were quite big, 400kW, and about half were four quadrant - reversible and regenerative modes included.
The supply was from a 24-pulse rectifier producing 700Vdc and rated at about 6,000Adc. The DC bus had a couple of huge capacitor banks comprising hundreds of electrolytic capacitors.
We didn't have the facilities in our works to load test these drives at their full power rating. The current, the volts, but not both at the same time.
But a colleague and I decided that a thermal run at full chat would be a good idea. We devised a test on site. Run one drive motoring and the in regeneration. The DC bus just supplies the losses.Simple, brilliant, ingenious. We rather liked the idea.
We set it up using two DC machines that were part of Ward-Leonard system - kit that we were replacing. OK. We ran it up and left the test running for a couple of hours. All good.
Then we came to stop it. In what sequence? Well obviously stopping the motor powering the test set would remove the power input. Wouldn't it? So that's what I did.
Brain fade hardly describes what happened next. The regen drive kept regenerating into the DC link. With no power being consumed, the regen pumped up the DC link voltage. Beyond the limits of the capacitors.
Capacitors blew up like improvised explosive devices and the carnage seemed to last forever....lit up the substation walls with one blue flash after another.
The implement of electrical destruction was me. myself, and I.