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07-01-2012, 01:32 PM #14
07-01-2012, 01:43 PM #15Professional Member
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- May 2011
07-01-2012, 01:50 PM #16
That is not to say that you should not seek out an answer to your question. Just realize one is wisdom the other is knowledge.
Engineers like to solve problems. If there are no problems handily available, they will create their own." Scott Adams
"We can't solve problems by using the same kind of thinking we used when we created them."
07-01-2012, 01:50 PM #17Regular Guest
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- Jun 2012
It goes so much more in depth than that though. A lot of electrical engineers (I didn't say all) would not be able to remember the physics behind all of this unless they use it every single day. I know I had a better understanding of it a few years ago. Use it or lose it...
07-01-2012, 02:15 PM #18
Although it's important to have a thorough understanding of the principles of electricity and how individual components effect the operation and power quality of a circuit it's not knowledge that you're going to be using in the field as a tech.
I use to be into electronic hobby building and avionics so the study of components in both AC and DC circuits actually interest me to a great deal.
In response to your first post the effects of capacitance and inductance on a AC circuit as far as you should be concerned relate to over all power quality.
Power quality can be expressed as that circuits power factor which is a ratio of real power to apparent power. It's a measure of the efficiency of the power in a circuit and is expressed on a scale of 0 to 1.
Real power is the power that actually performs work and apparent power is the effect of resistance, inductance and reactance in the circuit.
Both capacitors and inductors store energy. Capacitors store it in their electric field and inductors store it in their magnetic field. The combinations of these two elements in a circuit with resistance add up to that circuits total reactance. Also note that capacitance and inductance change with frequency.
Since frequency is constant ( 60 hz ) it's not an issue in typical linear power distribution.
So in purely resistive linear circuit the current and voltage waveforms are in synch and your power factor is very close to 1.0
It's at it's most efficient. Once you start adding inductance, ( motors, relays, lamp ballast, etc ) and capacitance ( DC power supplies in computers and servers, and wire and cable have some capacitance ) you start lowering the power factor and that circuits efficiency and start adjusting the phase angle of current to voltage ( Voltage will Lead Current ) which will increase overall power consumption.
Most buildings and especially industrial sites have a large inductive loads. ( big motors) and may require the addition of capacitor banks to correct the low power factor or pay a penalty to the utility company.
You might see a capacitve bank sitting next to a pump motor or next to a service panel that feeds a number of electric motors. They're trying to increase their power factor.
Capacitors and inductors in DC circuits have a variety of uses and unless your planning on getting into component level trouble shooting on circuit boards you don't need to waste time studying their many applications.
07-01-2012, 02:29 PM #19
If I was to continue in my career with only troubleshooting units of say 10 tons or smaller and basically be able to say "yup, change the board" or "yup, add a hard start kit" then for sure I would agree with your summarization of the importance of this type of stuff.
The fault I have made in my apprenticeship thus far, and what I am trying to correct, is by listening to those who have said "just get a general understanding because you won't need to know that in the field".
This perspective towards understanding only a portion of what I have been taught in school has been literally CRIPPLING when it comes to being able to apply a skill-set and knowledge-base from one type of equipment onto something different.
The best technicians I have known and still know, and ALL of the mentors and live resources I turn to have extensive knowledge of not only electrical theory but also of refrigeration theory and refrigerant properties- characteristics that are FAR from common amongst most techs I have met here in B.C.
The limited exposure I have had to larger scale refrigeration equipment tells me that when the day comes that I get called out to a plate style cooler system for a dairy tank with 50K of milk in it or to a 70 ton chiller system for a 40 story tower, I sure as HELL be a lot better on my theory than what would consist of a general understanding.
I know that I probably come across to MANY as a young cocky know it all little $#!T but please believe me when I say that with every piece of knowledge I learn, read, see, or am taught comes with about 10 pieces that I feel anxious about until I learn (and no, I don't need to do the math on that equation to realize it's impossibility- LOL)
But enough ranting for now- I'm probably overdue for a good punch in the teeth right about now anyways!
07-01-2012, 03:18 PM #20
Your post is a good example of how experience or lack of affects our perceptions of what's important and practical.
The example you used of voltage and current waveforms leading or lagging was explained ( did you read my entire post? ) in context to our industry. If you want to pursue their characteristics as applied to DC theory GO BACK to school. Or rather enroll in a school that focus' on electronics. ( hope your smart because it's an entirely different animal than simple AC power distribution.)
I've been in the industry for almost twenty years and have worked on everything from large kilo-ton centrifugal chillers to small 5 ton package units.
My knowledge of electrical theory as applied to our industry and electronics is pretty extensive. Do I know everything ? No, I do possess some humility.
That said I have yet to pull out my pocket note book and work through the electrical mathematic principles of a 100 ton air cooled chiller for purposes of trouble shooting.
Understand the engineering aspect of the machine and the sight where it's located where worked out by people most likely more knowledgeable than yourself far before you arrived.
As a tech I'm under obvious time constraints and it's my responsibility to quickly narrow down the offending component or issue causing the issue and repair it using correct service techniques without cutting corners and get to my next service call.
If it's going to take a day or two to order in parts then let the customer know and then hit the road.
What's important is understanding the specific functions of the specific type of equipment you're working on. Also a thorough understanding of the components and principles of refrigeration in general.
IF you walk up on a 70 ton chiller that's off on high pressure do you need to know how to figure for total inductance ( XL = 2πfL ) ? Are you going to be wasting time connecting a oscilloscope and watching sinusoidal waveforms shoot across a screen ? No you need to be focused on the problem at hand.
Nothing wrong with having a good base of education but because of your experience level you don't know what information is going to be useful to you.
When guys who have been in the field for 20 years tell you what you need to focus on why would you question that ?
07-01-2012, 03:30 PM #21
Hey very well said six, and I humbly salute thrice you, your comment, and foremost your expertise. My problem, however, has been learning where to draw the line and understanding what exactly falls under the umbrella of 'necessary knowledge'. I can't even begin to tell you how many examples I've had where I have been going in depth even a LITTLE bit on a call and had some instructor or previous journeyman's vioce in the back of my head haunting me with words of, "aawww $#!T- don't spend too much time on that, you'll NEVER need it in the field". Case in point: Psychometrics and enthalpy charts. I'll bet you that a total of 3 techs I have ever come across have said they've used them outside of the classroom. On a site like this, that I truly believe has some of the brightest minds from our industry, I think the percentage of guys who use them regularly would be a tad different. Hence why long ago I went back to my notes from school and hammered them into my brain a little bit harder.
And so the question again then is dually: IS it just the school of hard knocks and you learn what you need to as you go? Or can someone like yourself give a good general recommendation of what kind of material a guy like myself can bury his nose in to raise above the general 'cliff notes' that 8 weeks of school a year gives you, without getting too carried away in the world of electronics theory?
and p.s: re: your answer to the original question, I DO genuinely apologize for not thanking you for your response previously.
07-01-2012, 04:32 PM #22
. I think my self and mybe a few techs that specialize in different aspects of our industry could give you a good understanding of what knowledge is necessary.
But that advice doesn't mean you have to stop learning and judging by your previous post it doesnt sound like you're going to.
So I commend you for having a thirst of knowledge and dont ever let someone talk you into lowering your standards on what youre interested in or what you feel is relevant.
Stay humble. Keep learning. and asking questions. Your value as a technician will be based on things like dependabillity, effectivness and eventually experience.
Maintain a high set of standards and a strong work ethic. The knowledge will come with experience.
07-01-2012, 04:36 PM #23Regular Guest
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- Jun 2012
I encourage learning. Having said that your view is similar to saying that a blacksmith needs to be a metallurgist to be a truly great tradesman. A thorough understanding of it has no bearing on their artistry really. I highly doubt you will have an oscilloscope next to vac pump on the truck at all times. To know what causes problems doesn't require a lot of physics. You stick your clamp on ammeter on a motor wire and see a higher than normal amp draw. A solid basic knowledge of electricity will allow you to find the issue, just rule mechanical issues in this case. A clamp on ammeter is a fantastic example of useful inductance by the way. Keep us posted on your progresses too. You're ambitious and it shows.
07-01-2012, 04:51 PM #24
Thanks a lot guys. excellent feedback once again
07-01-2012, 07:26 PM #25Professional Member
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- Feb 2007
- Central NJ
07-01-2012, 08:08 PM #26
Forest won't get you "too carried away," although he is one of the foremost experts in the field.
Any "first semester" course in electronics will give you all the basics you need, and that is Forest's approach.