Need help for designing Power board of Water Pumps

[Cochav]

I have recently graduated in EE and I`m in the process of getting my first job.
I have been asked to provide an answer to this question for a job selection process.

I am not sure how to approach the question, what specifically I should be looking for. Any insights on understanding the process for achieving the design would be much appreciated. I have been told this shouldn't be a hard question, but without any previous experience, I`m in need of advice.

There is circuit plan with two cans of water. One of them has a water entrance coming from some other process. For each can, there are 3 height sensors.
A plan is needed to plan a control for the water pumps to meet the process requirements. Electrical control without a controller.

Process Requirements:

1. The water should stay in containers for the maximum amount of time.
2. There should be no gliding from the container
3. A working light should be turned on.
4. A malfunction lamp should be turned on.
5. The pumps operate according to the planned command.

The power board of the pumps should be designed

 

[MacGyverS2000]

So your potential new job has given you a test... and your first inclination is to cheat on it by asking others how to solve it? If you can't solve it (by yourself) to their satisfaction, it's a good indication you do not have the skillset they are looking for.

<SMH>

Dan - Owner

http://www.Hi-TecDesigns.com

 

[waross]

Do you have any other job prospects?
This one doesn't look good.
Load sharing between the 3hp pump and the 3 Kilo watt pump may be interesting.
Will both these pumps be supplied with the same voltage?
Is pump P3 controlled by this board or by the process.
Despite the number of questions that you have asked us, there are some questions that you should have asked the interviewer about the desired operation.
By not asking those questions you have probably already failed the interview.
Sorry. It's called tough love.
p.s. I may be of an age. See thread1088-434846

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[IRstuff]

I don't think anyone realistically expects you to actually design a controller panel to the point of creating drive voltages, etc.

I think that you failed because this was a reasoning problem, not a design problem. I think the following thought process would have gotten you close to a pass. A typical interviewer has only about an hour to interview someone, if that long; a complicated design problem is not practical for that situation.

> P3 is turned on if all 3 level switches in Tank2 and Tank1 are tripped --> ON light is turned on, if P3 does not turn on, fault light is turned on
> If LSH in any tank is tripped without the lower level sensors being tripped, then there's a fault and the fault light is turned on
> P2/P1 are turned on if all 3 level switches in Tank1 are tripped --> ON light is turned on, if P2/P1 do not turn on, fault light is turned on -- there are nuances here, since the maximum flow is limited by P3, so the interviewer might have only wanted you to turn on P1.

I would mark you, or whoever did the drawing, failed also for writing Kw, instead of the correct kW. If that was provided by the interviewer, you should have called them on it.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[LionelHutz]

It's very open to interpretation. The first step is to create rules for when the pumps should start and stop based on the level switches, for when the work light should be on and for when the fault light should be on. Then go through all possible combinations and make sure the rules meet the requirements and also make logical sense. Making logical sense is probably as important and meeting the requirements. They might even want you to point out why something doesn't make logical sense.

 

[roydm]

When faced with a task like that you have to be very diplomatic

Approach it from the point that the interviewer has no idea either LOL

Good Luck, let us know if you make it.

BTW, if you don't know how to do something isn't it better to ask how?

 

[waross]

Simple example;
Simple solution.
Power on the board, ON light is on
LSH, LSH, LSL, and LSL switch on the FAULT light.
LSM controls the appropriate pump.
If there are conditions that make this solution unusable, the conditions should have been given.

Bill
--------------------
"Why not the best?"
Jimmy Carter