Author: ABBdriveX

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AQ: Is it worth to built-in batteries in electric cars

Energy storage is the issue. Can we make batteries or super caps or some other energy storage technique that will allow an electric car to have a range of 300-500 miles. Motors and drives are already very efficient, so there is not much to be gained by improving their efficiency. As far as converting the entire fleet of cars to electric, I don’t expect to see this happen any time soon. The USA has more oil than all the rest of the world put together. We probably have enough to last 1000 years. Gasoline and diesel engines work very well for automobiles and trucks and locomotives. The USA also has a huge supply of coal, which is a lot cheaper than oil. Electricity is cheaper than gasoline for two reasons: Coal is much cheaper than oil, and the coal fired power plants have an efficiency of about 50%. Gasoline engines in cars have a thermal efficiency of about 17%. Diesel locomotives have an efficiency of 50%+.

I don’t believe the interchangeable battery pack idea is workable. Who is going to own the battery packs and build the charging stations? And what happens if you get to a charging station with a nearly dead battery and there is no charged battery available?

Who is going to build the charging stations; the most logical answer is the refueling station owners as an added service. The more important question is about ownership of the batteries. If as an standard, all batteries are of same size, shape, connectors as well as Amp-Hour (or kWh) rating and a finite life time, lets say 1000 recharging. The standard batteries may have an embedded recharge counter. The electric car owners should pay the service charges plus cost of the kWh energy plus 1/1000 of the battery cost. By that, you pay for the cost of new batteries once you buy or convert to an electric car and then you pay the depreciation cost. This means you always own a new battery. The best probable owner of the batteries should be the battery suppliers or a group or union of them (like health insurance union). The charging stations collecting the depreciation cost should pass it on to the battery suppliers union. Every time a charging station get a dead battery or having its recharge counter full, they will return it to the union and get it replaced with a new one. So, as an owner of electric car you don’t need to worry about how old or new replacement battery you are getting from the charging station. You will always get a fully charged battery in exchange. The charging stations get their energy cost plus their service charges and the battery suppliers get the price of their new battery supplies.

Buddies, these are just some wild ideas and I am sure someone will come up with a better and more workable idea. And we will see most of the cars on our roads without any carbon emission.

AQ: Maximum permissible value of grounding resistance

For grounding in the US it typically goes like this: Utility transformer has one ground rod. Then from the utility to the building you typically have three phase conductors and one neutral/ground conductor landing on the main panel with the utility meter. At that point we drive a ground rod. And we bond the ground rod to the water pipes (generally). And we bond the ground rod to the building steel (generally). Water pipes are generally very well connected to ground and the building steel is a nice user ground. With all these connections you typically have a good ground reference. Now, if that utility neutral wire is bad or too small, then you can have poor reference to ground between phases (a normal sign of that is flickering lights even when the load is not changing much).

Grounding impedance of the transformer and building ground rods is mainly for voltage stabilization and under normal conditions should have nothing to do with our return ground fault current. See NEC 250.1 (5) “The earth shall not be considered as an effective ground-fault current path.”

Let’s say we have a system with the building transformer and panel to ground impedance of 1000 ohms (we built this place on solid rock). Okay, we have a poor 277V reference and we will have flickering lights (that 277 voltage will bounce all over the place). But now, in our system above, if we take a phase wire and connect it to a motor shell, which is also connected to our grounding wire, will the upstream breaker trip? The answer is yes. If our phase-to-ground fault impedance is low we will trip the upstream feeder breaker no matter what the main panel ground rod impedance is. My point here is that is does not matter what our transformer grounding is or what our panel grounding is (ground rod is not important in this case). The breaker must trip because our circuit is complete between the phase conductor and the transformer wye leg.

As long as we have a utility main transformer to panel neutral conductor of proper size to handle our fault current and we size our grounding conductors properly and they are properly connected at each subpanel and each motor in our case, we will apply nearly full phase to ground voltage because our real ground fault path is from that motor, through the grounding conductor, through our sub panels, to our main panel, than back to the transformer. That ground current must flow through our building grounding conductor to the main panel and back to the transformer through that utility neutral wire which is connected to the wye leg of the transformer. And it does not matter what the transformer to ground rod connection is. We could take that out the transformer to ground rod connection and the main panel to ground rod connection completely and we are still connecting that phase wire, through the motor metal to the grounding conductor back to the wye leg of that utility transformer, which will complete our electrical circuit. Current will flow and the breaker will trip.

AQ: Avoid voltage drop influence

My cable size and transformer size should give me maximum 3% on the worst 6% to 10%. If it is the single only equipment on the system then maybe you can tolerate 15%. If not, dip factor may affect sensitive equipment and lighting.

This is very annoying for office staff each time a machine starts lights are dimming. It does not matter what standard you quote I cannot accept 10%- 15% make precise calculation and add a 10% tolerance to avoid.

In most cases, this problem comes from cable under sizing so we have to settle with a Standard giving 15% Max.

Just recently I had to order a transformer and cable change for a project which was grossly undersized.
I have had to redesign the electrical portion of a conveyor and crushing system to bring the system design into compliance with applicable safety codes. The site was outdoor at a mine in Arizona where ambient temperatures reach 120F. The electrical calculation and design software did not include any derating of conductor sizes for cable spacing and density within cable trays, number of conductors per raceway, ambient temperature versus cable temperature rating, etc. Few of the cables had been increased in size to compensate for voltage drop between the power source and the respective motor or transformer loads.

Feeder cables to remote power distribution centers were too small, as voltage drop had not been incorporated in the initial design. The voltage drop should not be greater than 3%, as there will be other factors of alternating loads, system voltage, etc. that may result in an overall drop of 5%.

The electrical system had to be re-designed with larger cables, transformer, MCCS, etc, as none of the design software factors in the required deratings specified in the National Electric Code NFPA70 nor the Canadian Electric Code, which references the NEC.

AQ: How to design an Panel required for PLC / MCC / Drive

1. The regular industrial standard size panel available with most of the panel fabricator’s.
2. Type of protection (used to say as IP).
3. Spacing depends upon the Power handled by the conductors inside Panel and the ventilation system.
4. Cable Entry / Bus bar entry may depend on the application and site condition. it may be at rear/bottom or at the top.
5. When comes to Drive, if the site condition is too hot then an industrial ac is required usually attached at the side of the panel.
6. Drive to drive required spacing (Check the manual of the drive}, since the power switching activity take place inside the drive.
7. Provide required space for the transformers and AC-choke since they create magnetic flux in ac circuits.
8. Don’t mix the Control cable, Power cable, Signal cable and Communication cable together in the cable tray… Otherwise you will be wired…
9. Keep the control on mcb/mccb/mpcb in handy location. So that its easier for operator to control it frequently and not disturbing other circuits..
10. Plc will be acquiring the top position in the panel since there is nothing to do with it once installed. Just we will be monitoring the status.
11. Don’t place the Plc nearby to the incoming or outgoing heavy power terminals..
12. Mcc panel are easy thing to do, but do the exact calculation for the ACB selection in the incomer side. Since each feeder will be designed with tolerance level.

There being a lot more than 12 guidelines to follow. What
about back-up power for the PLC? What about internal heat flow considerations
(not just does it need an AC or not)? How much space between terminal blocks
and wireway? What about separate AC and instrument grounds? What about wireway
fill? What about wire labels? What about TSP shields? What about surge
protection? In my experience, there are plenty of people that can design a
panel but if they haven’t gone to the field with it then they haven’t been able
to learn from their design mistakes.

The best thing you can do is start your design but you
really need to be guided by an experienced designer.

AQ: Grain Storage system

A Grain Storage system usually consists of the following elements

1. A means of measuring Grain coming in and out- Usually a truck scale or a bulk weighing system. In addition some applications require measuring grain between transfers to different bins and a bulk weighing system is usually used for that.

2. A means of transferring between different operations or storage location- Conveyors, screws, buckets, pneumatic, wheel house.

3. Dust Collection

4. And Equipment for the operations that will be performed, drying, cleaning, screening, grading, sampling, roasting, steaming, packaging etc.

A system I have just completed was 24 containers + 3 buildings for storage with 76 conveyors, 3 drop-off and 3 loading points. Connection to ERP system and weigh scales to weigh trucks and send them to the correct bay. Local HMI on each bay ensured correct lorry goes to correct bay. Main conveyor runs are automatically selected. Manual option to run all conveyors to move grain around.

System used Ethernet infrastructure with hubs mounted strategically around tank farm. Also implemented soft starter with Ethernet connectivity, thus allowing easy monitoring of current consumption + for maintenance.

The future-proof design will allow customer to install level and humidity measurement in the future using the Analogue IO connected on Ethernet.

AQ: PPE (Personal Protective Equipment)

When I think of using PPE as a controls engineer, I think
about electrical shock and arc-flash safety in working with electrical devices.

The PPE (Personal Protective Equipment) requirements to work on live electrical
equipment is making doing commissioning, startup, and tuning of electrical
control systems awkward and cumbersome. We are at a stage where the use of PPE
is now required but practice has not caught up with the requirements. While
many are resisting this change, it seems inevitable that we will need to wear
proper PPE equipment when working on any control panel with exposed voltages of
50 volts or more.

With many electrical panels not labeled for shock and arc-flash hazard levels,
the default PPE requires a full (Category 2+) suit in most cases, which is very
awkward indeed. What can we do to allow us to work on live equipment in a safe
manner that meets the now not so new requirements for shock and arc-flash
safety?

Increasingly the thinking is to design our systems for shock and arc-flash
safety. Typically low voltage (less than 50 volts), 120VAC, and 480 VAC power
were often placed in the same control enclosure. While this is cost effective,
it is now problematic when wanting to do work on even the low voltage area of
the panel. The rules do not appear to allow distinguishing areas of a panel as
safe, while another is unsafe. The entire panel is either one or the other. One
could attempt to argue this point, but wouldn’t it be better to just design our
systems so that we are clearly on the side of compliance?

Here are my thoughts to improve electrical shock and arc flash safety by
designing this safety into electrical control panels.

1. Keep the power components separate from the signal level components so that
maintenance and other engineers can work on the equipment without such hazards
being present. That’s the principle. What are some ideas for putting this into
practice?

2. Run as much as possible on 24VDC as possible. This would include the PLC’s
and most other panel devices. A separate panel would then house only these shock
and arc-flash safe electrical components.

3. Power Supplies could be placed in a separate enclosure or included in the
main (low voltage) panel but grouped together and protected separately so that
there are no exposed conductors or terminals that can be reached with even a
tool when the control panel door is opened.

4. Motor Controls running at anything over 50 volts should be contained in a
separate enclosure. Try remoting the motor controls away from the power devices
where possible. This includes putting the HIM (keypad) modules for a VFD
(Variable Frequency Drive) for example on the outside of the control panel, so
the panel does not have to be opened. Also, using the traditional MCC (Motor
Control Centers) enclosures is looking increasing attractive to minimize the
need for PPE equipment.

For example “finger safe” design does not meet the requirements for arc-flash
safety. Also making voltage measurements to check for power is considered one
of, if not the most hazardous activity as far as arc-flash goes.

AQ: Industrial automation process

My statement “the time it takes to start or stop a process is immaterial’ is somewhat out of context. The complete thought is” the time it takes to start or stop a process is immaterial to the categorization of that process into either the continuous type or the discrete type” which is how this whole discussion got started.

I have the entirely opposite view of automation. “A fundamental practice when designing a process is to identify bottlenecks in order to avoid unplanned shutdowns”.

Don’t forget that the analysis should include the automatic control system. This word of advice is pertinent to whichever “camp” you chose to join.

Just as you have recognized the strong analogies and similarities between “controlling health care systems” and “controlling industrial systems”, there are strong analogies between so-called dissimilar industries as well between the camp which calls itself “discrete” and the camp which waves the “continuous” flag.

You may concern about the time it takes to evaluate changes in parameter settings for your cement kiln is a topic involving economic risks which could include discussions of how mitigate these risks, such as methods of modeling the virtual process for testing and evaluation rather than playing with a real world process. This is applicable to both “camps”.

The same challenge of starting up/shutting down your cement kiln is the same challenge of starting up/shutting down a silicon crystal reactor or wafer processing line in the semiconductor industry. The time scales may be different, but the economic risks may be the same — if not more — for the electronics industry.

I am continuously amazed at how I can borrow methods from one industry and apply them to another. For example, I had a project controlling a conveyor belt at a coal mine which was 2.5 miles long – several millions of pounds of belting, not to mention the coal itself! The techniques I developed for tracking the inventory of coal on this belt laid the basis for the techniques I used to track the leading and trailing edge of bread dough on a conveyor belt 4 feet long. We used four huge 5KV motors and VFDs at the coal mine compared to a single 0.75 HP 480 VAC VFD at the bakery, and startups/shutdowns were order of magnitudes different, but the time frame was immaterial to what the controls had to do and the techniques I applied to do the job.

I once believed that I needed to be in a particular industry in order to feel satisfied in my career. What I found out is that I have a passion for automation which transcends the particular industry I am in at the moment and this has led to a greater appreciation of the various industrial cultures which exist and greater enjoyment practicing my craft.

So these debates about discrete vs. continuous don’t affect me in the least. My concern is that the debates may impair other more impressionable engineers from realizing a more fulfilling career by causing them to embrace one artificial camp over the other. Therefore, my only goal of engaging in this debate is to challenge any effort at erecting artificial walls which unnecessarily drive a damaging wedge between us.

AQ: Automation engineering

Automation generally involves taking a manufacturing, processing, or mining process that was previously done with human labor and creating equipment/machinery that does it without human labor. Often, in automation, engineers will use a PLC or DCS with standard I/O, valves, VFDs, RTDs, etc to accomplish this task. Control engineering falls under the same umbrella in that you are automating a process such as controlling the focus on a camera or maintaining the speed of a car with a gas pedal, but often you are designing something like the autofocus on a camera or cruise control on an automobile and oftentimes have to design the controls using FPGA’s or circuits and components completely fabricated by the engineering team’s own design.

When I first started, I started in the DCS side. Many of the large continuous process industries only let chemical engineers like myself anywhere near the DCS. EE landed the instruments and were done. It was all about you had to be process engineer before your became a controls engineer. In the PLC world it was the opposite, the EE dominated. Now it doesn’t line up along such sharp lines anymore. But there are lots people doing control/automation work that are clueless when comes to understanding process. When this happens it is crucial they are given firm oversight by someone who does.

On operators, I always tell young budding engineers to learn to talk to operators with a little advice, do not discount their observations because their analysis as to the cause is unbelievable, their observations are generally spot on. For someone designing a control system, they must be able to think like an operator and understand how operators behave and anticipate how they will use the control system. This is key to a successful project. If the operators do not like or understand the control system, they will kill a project. This is different than understanding how a process works which is also important.

AQ: Hazardous area classification

Hazardous area classification has three basic components:
Class (1,2) : Type of combustible material (Gas or Dust)
Div (I, II) : Probability of combustible material being present
Gas Group (A,B,C,D): most combustible to least combustible (amount of energy required to ignite the gas)

Hazardous Area Protection Techniques: There are many, but most commonly used for Instrumentation are listed below:
1) Instrinsic Safety : Limits the amount of energy going to the field instrument (by use of Instrinsic Safety Barrier in the safe area). Live maintenance is possible. Limited for low energy instruments.
2) Explosion proof: Special enclosure of field instrument that contains the explosion (if it occurs). Used for relatively high energy instruments; Instrument should be powered off before opening the enclosure.
3) Pressurized or Purged: Isolates the instrument from combustible gas by pressurizing the enclosure with an inert gas.

Then there are encapsulation, increased safety, oil immersion, sand filling etc.

Weather protection: Every field instrument needs protection from dust and water.
IP-xy as per IEC 60529, where
x- protection against solids
y- protection against liquids
Usually IP-65 protection is specified for field instruments i onshore applications (which is equivalent of NEMA 4X); IP-66 for offshore application and IP-67 for submersible service.

AQ: Self Excited Induction Generator (SEIG)

The output voltage and frequency of a self excited induction generator (SEIG) are totally dependent on the system to which it is attached.

The fact that it is self-excited means that there is no field control and therefore no voltage control, instead the residual magnetism in the rotor is used in conjunction with carefully chosen capacitors at its terminal to form a resonant condition that mutually assists the buildup of voltage limited by the saturation characteristics of the stator. Once this balance point is reached any normal load will cause the terminal voltage to drop.

The frequency is totally reliant upon the speed of the rotor, so unless there is a fixed speed or governor controlled prime mover the load will see a frequency that changes with the prime mover and drops off as the load increases.

The above characteristics are what make SEIGs less than desirable for isolated/standalone operation IF steady well regulated AC power is required. On the other hand if the output is going to be rectified into DC then it can be used. Many of these undesirable “features” go away if the generator is attached to the grid which supplies steady voltage and frequency signals.

The way around all the disadvantages is to use a doubly fed induction generator (DFIG). In addition to the stator connection to the load, the wound rotor is provided with a varying AC field whose frequency is tightly controlled through smart electronics so that a relatively fixed controllable output voltage and frequency can be achieved despite the varying speed of the prime mover and the load, however the costs for the wound rotor induction motor plus the sophisticated control/power electronics are much higher than other forms of variable speed/voltage generation.