Electrical talk: 12-3 power cord vs romex

rstreet

rstreet

Well Known Member
Supporting Member 17
bobs409 said:
It works! No smoke or sparks either. :D

You can view the amp draw so with it running very slow (4 hertz), it was pulling about 7 amps but at full speed (60 hertz) it was only 2.8 amps. That is just the motor, not even a wheel mounted to it.
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Bob your description above is spot on. I remember at an early age many many years ago working with centrifugal pumps electrical loads in wells and sewer pump stations and scratching my head. Then processor based variable frequency drives were introduced and I went into over load!
Ray used to work with that stuff also so I have an understanding bond as to why he shot the turkey that wasn’t going anywhere in his freezer!
Robert
 
55Brodie

55Brodie

Well Known Member
bobs409 said:
It works! No smoke or sparks either. :D

You can view the amp draw so with it running very slow (4 hertz), it was pulling about 7 amps but at full speed (60 hertz) it was only 2.8 amps. That is just the motor, not even a wheel mounted to it.
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Just curious as to what motor speed range you anticipate running when all is said and done. You might want to play with the SVC (sensorless vector control) mode versus the default Volt/Hertz mode. You can emulate servo performance in SVC mode.
 
bobs409

bobs409

 
Administrator
55Brodie said:
Just curious as to what motor speed range you anticipate running when all is said and done. You might want to play with the SVC (sensorless vector control) mode versus the default Volt/Hertz mode. You can emulate servo performance in SVC mode.
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As soon as I figure out what you asked, I'll give you an answer. :D

Not sure on what speeds will be best as I've never used a belt grinder before but probably based on material and belt grit. I will be adding a potentiometer to my control panel so will be easy to control up or down.
 
wristpin

wristpin

Well Known Member
One of our VFD pumps at work we run at 40-60Hz. One of the geniuses here found that the VFD would go to 80Hz. So he turned VFD to 80Hz after getting informed "could" and "should" are not the same. Pump motor fried within minutes. But....80Hz wasnt the cause it was just coincedence. :crazy
 
55Brodie

55Brodie

Well Known Member
wristpin said:
One of our VFD pumps at work we run at 40-60Hz. One of the geniuses here found that the VFD would go to 80Hz. So he turned VFD to 80Hz after getting informed "could" and "should" are not the same. Pump motor fried within minutes. But....80Hz wasnt the cause it was just coincedence. :crazy
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It was NOT coincidence. Your genius was obviously ignorant of the affinity laws for fans and pumps. In your example, turning the VFD to 80 Hz now requires 2.35 times the original motor horsepower.
 
wristpin

wristpin

Well Known Member
bobs409 said:
Just an update, I just replaced the 12-3 with some 12-4 so I'm ready for inspection! (it was bugging me being the purist that I am) ;)
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I'll buy 17 inched of that 12-3 or $0.02 a foot if you'll pay for the overnight shipping. Maybe save shipping costs and drive it to me. Grab me a Wendy's Baconator while you're driving anyway :smoke you're a sweetheart
 
Don Carvill

Don Carvill

Well Known Member
I am a retired electrician. I was going to make a comment, but every body else has it covered. the only thing I would like to add is that you are dealing with common industry terms. When I say 12-3 I assume it means 2 hots, 1 neutral, and a ground wire is included. But you know what you do when you assume...
 
bobs409

bobs409

 
Administrator
Don Carvill said:
I am a retired electrician. I was going to make a comment, but every body else has it covered. the only thing I would like to add is that you are dealing with common industry terms. When I say 12-3 I assume it means 2 hots, 1 neutral, and a ground wire is included. But you know what you do when you assume...
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It does mean that in Romex but power cords must play by a different set of rules. :laugh4

Anyone want to buy a 6' piece of 12-3 power cord?? :laugh2 Maybe I'll make an extension cord out of it. :think
 
Don Carvill

Don Carvill

Well Known Member
That is true. When I needed a piece of SO cord I did look to see if it had the ground.
I am out of it now, but in the last 35 years it seemed like the most changes occurred in the area of grounding.
I used to enjoy talking codes, ampacity, and grounding requirements, but when I think of it these days it makes my head and neck hurt.
Maybe that is what it is like to get old. For some reason I can still go out in the barn and look at, or work on my Impala all day. Especially now that Spring is on it's way.
 
409gang

409gang

Well Known Member
Supporting Member 1
rstreet said:
What does SO stand for?
Robert
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It is a highly flexible and oil resistant cable of which there are many different types, SO, SOO, SOW, SOOW, SOJ etc. Each one has a different insulation depending on its application with the most common one being SO. Most people just call it rubber cord unless your in the trade. All wire is classified by its insulation of which there are to many to mention, you have to apply the right wire for its intended use. Each classification has different usages i.e. underground, sunlight, oil, gas etc. and an electrician has to use all wire within its classification.
 
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