Electrical Anecdotes

look at this !

2012-01-16T19:28:00.000-08:00

I came across a blog by name sherlock ohms where readers share their experiences while working with electrical and electronic systems. Here is one incident.....

A quick remedy !

2010-09-28T06:38:00.000-07:00

As is the practice, I.A.S.(Indian Administrative Service) Officers get routinely transferred from one department to other. These departments could be as diverse as they go.

Once, such an officer ,who was heading Rajasthan State Roadways Corporation was transferred as the Chairman of Rajasthan State Electricity Board ( RSEB).He was a dynamic officer and was eager to show progress.The progress of construction of Transmission lines was very slow and field officers failed to explain the reason.He called meeting of all top officials.

"Where is the bottleneck" The Chairman thundered.

" Sir, stringing can not be done with out Conductor." The Chief Engineer replied hesitantly.

" Don't worry.I think I can certainly do something here.I recently suspended 50 conductors working with Road ways.I will request The Chairman Rajasthan State Roadways Corporation to
reinstate them and transfer them to RSEB."

-------- Contributed By DN Joshi , Jodhpur

A REASONABLE LIMIT !

2010-02-17T04:55:00.000-08:00

After 1977,when Mrs.Indira Gandhi lost the election,there was a sudden vacuum in politics and a number of new local political leaders had sprung up.

A 132 KV substation had just been commissioned and I was asked to operate it till a new Engineer was posted.
A newly born leader visited the substation.He was very skeptic about we engineers and held a notion that engineers were the cause of chronic power shortage. I took him around.

"Nicely constructed.Very good" He said
"Thank you sir"
"What is this?" he asked pointing towards the control panel.
"132KV supply Incoming from Jodhpur"
"And this?"
"33KV out going supply to Tiwari"*
"This ?"
"33KV out going to Mathania"*
"And the last one?"
"33KV outgoing to Osiyan"*
"33+33+33=99,What about the balance 33?"
"कुछ तो हमारे लिए भी रहने दीजिये " ("We need to survive too")
"Ok,ok. but it is too much. Reduce it to a reasonable limit. Availability of power to our cultivators is not enough."
( * Name of the places in Rajasthan)

-------- contributed by DN JOSHI

"Current" less water !

2009-06-30T04:55:00.000-07:00

In the early sixties,a major Hydro-electric project was set up known as Bhakra Nangal Project.The concept of generating electricity from river was rather a novelty to the local community.The farmers in the surrounding regions were dependent upon water from the downstream of the project.

A group of farmers felt that there was a fall in the yield of the crop in their fields in the year immediately following the year of the commissioning of the project.They came up with an idea that the fields are being supplied with "sapreta"( a local term usually used for milk from which fat has been removed i.e. toned milk) water. The feeling was that "current"or "essence" has been extracted from the water rendering it "ineffective and incapable" of nurturing the crop leading to a drop in the yield.
As bad news travels faster, a panic like situation was created amongst the local community which could have culminated into a major agitation.

Fortunately local leaders intervened and explained the matter to the agitated farmers and thus a major crisis could be averted.

Meters without pointers !

2008-09-29T21:27:00.000-07:00

I got a call and the caller sounded frantic. Normally, he is a very composed person and an extremely efficient store keeper. He explained to me that there was an inventory audit going on and the auditor was refusing to believe that the material shown matched its description. Not only that, he was threatening to report the matter to the higher ups. Ah, that was serious.

I walked over to the store and found that I knew the auditor because he had audited the inventory of equipment in my department - Quality Assurance, the previous year.

After the initial pleasantries, I asked him what the problem was. He became serious again and told me that the storekeeper was showing some tiny little stuff as potentiometers. I looked at what was offered and said that they were indeed potentiometers. He looked puzzled and asked me, "Then where is the pointer? Don't all meters have pointers?"

---- J.L.Anil Kumar

Transformer Transformation

2008-08-28T01:24:00.000-07:00

During the early part of my teaching career, I joined an engineering college near Bangalore and took over as the Head of ECE department.
There was an immediate requirement of 12 Nos. of small transformers for the laboratory. I was informed that the procedure called for taking the indent personally to the Director of the institution (a non technical person), who would scrutinize the indent and authorize the ordering.
This Director had a reputation for being very strict and abrasive. This being my first encounter with him, I entered his chamber with great trepidation.
He scrutinized the indent and read the title “Transformers-12 Nos.”
He thundered, “Do you know what you are asking for!!! ”
“Y-Y-Yes Sir”, I mumbled.
“Do you know what would each transformer cost? ” he continued in the same tone.
“Er….. about Rs.30/-, Sir.”
“What!!! Do you take me for a fool? Do you think you technical people can take me for a ride? Do you want me to believe that those big units that I daily see when I ride to college could be had just for Rs. 30/- .”
I immediately understood the situation. For him, transformers meant the large distribution transformers one can see installed by the road side.
“Sir, if I may clarify, these are tiny transformer units meant for use inside our laboratory.”
All of a sudden the tone of the Director’s speech changed. He appeared mellowed and embarrassed and said “Ok, please go ahead and order 24 Nos. if you want. I am all for giving you technical people full freedom in your activities.”

------ K Sudheendra

"Geared-down" to troubleshoot !

2008-05-23T05:16:00.000-07:00

It was one of my earliest commissioning assignments. The job was ideal for a rookie. Just a 45 kW dc drive with very simple functionality. Start, stop and speed set potentiometer. The control panel was built with care and installed properly. All I had to do was to conduct routine checks and start the drive return home.
Cochin Kadalas (Kadalas means paper in Malayalam-Kerala, India) was the factory in which I had to do all this.
Everything went as per expectations. The only hitch was that the place was so hot and humid that, half an hour after I started my work, I looked as if I had fallen into a pool fully clothed and got out. I was sweating so profusely. When it became impossible to bear, I took my shirt off and that is the only time I have conducted official work so dressed, I mean, undressed.
When it was sure that the drive and the paper machine to it was driving were working as expected under no-load, paper pulp was made and conveyed to the machine. As soon as the pulp entered between the rollers the machine stopped. The ammeter indicated full rated current. I opened up the panel and increased the current limit to the rated overload limit. No change. The machine refused to work.
All kinds of investigations followed. But the situation did not change.
The machinery was installed by a man who barely spoke Hindi. All he knew was Bengali. With my broken Hindi and more broken Bengali, I tried to find out more about the machinery, with the hope of finding out the reason for the stalled machine. While we were having this conversation, he commented that he had very recently commissioned an identical machine successfully. I tried to interrogate him to find out if there was even a minor difference between that and this machine. He kept insisting that there were none.
While all this was going on, he let slip that the motor in the earlier case was a 750 rpm machine and that this one was ‘unnecessarily’ 1440 rpm.
Ah ha! The gearbox between the motor and the machine was also exactly as in the previous case.
Now it was clear that the motor was delivering half the power required because it was running at half the speed!
I had a tough time convincing the non-engineers that we either had to change the motor or the gearbox. Finally the latter was done and my one-day-assignment ended after nearly a week.

------ J L Anil Kumar

Problem ---- watered Down !

2008-05-10T16:00:00.000-07:00

My uncle told me this story from his own experience, a long time ago.He was a consultant to a beer manufacturing unit. The unit installed a new bottling plant and tried a dry-run. Everything went well except the bottle capping part. Bottle after bottle passed and the machine refused to cap them. After days of checking everything repeatedly, the man in charge sent for him.After taking a good look at the machine and how it operated, he placed a beer bottle filled with water. Promptly the machine capped it. The machine had weight sensors and was designed not to cap empty bottles !

-- J L Anil Kumar

Link to humour

2008-02-15T04:12:00.000-08:00

Here is a link to an interesting site on humour http://www.csrstds.com/humor.html

THE (UN)COMMON SENSE

2007-11-12T20:04:00.000-08:00

About 6 years ago I had to set up servers for my colleague at
a laboratory inside ALTTC (Advanced Level Telecom Training Centre),
Ghaziabad,Near Delhi. I hooked up the server, monitor, keyboard,
mouse and the works! I first switched on the monitor and next I
tried switching on the server but it refused to do so.

Based on my years of “on-the-job” experience, the first thing
I suspected was the SMPS. SMPS seemed to be order because the
power ‘ON’ LED on motherboard was on. Next, as a standard procedure, I pulled out all the peripheral cards, disconnected keyboard, mouse and all other
connections except the power cable and tried again.

 Still NO SIGN of server switching ON!

   Due to non-availability of CRO or such other testing equipment,
I could not test the motherboard and called up the supplier and
told all the symptoms, who advised me to bring it to Delhi, as he
 did not have service centre at Ghaziabad.  Meanwhile, I called up
 our Delhi office to borrow another server and after some initial
reservation they agreed but asked me bring along the ‘faulty’ server.

 We confidently connected power to the new server! But, still no sign
 of life!

 NOW I was really at my wit’s end! My whole confidence was at the
lowest ebb! By now it was late in the evening. Completely exhausted,
on an impulse I checked the supply voltage. It was 110V AC instead of
normal 220V AC, which one would normally expect. (We later found that
a special supply network of 110 V AC had been created for these
equipment supplied by Fujitsu, Japan.)

   But why did the monitor switch on at 110 V AC? Well it turned out
that the monitor had higher voltage tolerance range.

  Even today the remark of my boss keeps ringing in my ears “ Gana, 
sometimes you need to stop using too much of brain!”

 ---------   R. GANAPATHI RAO
Research Associate,CENTRE FOR DEVELOPMENT OF TELEMATICS,
ELECTRONICS CITY,BANGALORE.

Drilling Machine Drills

2007-01-06T19:23:00.000-08:00

Drilling machine mystery

Our ½ hp, 3ph, drilling-tapping machine is 10 years old. Recently, the 6A HRC fuse in the R phase blew, followed by tripping of the upstream ELCB.

Could it be an earth fault? Ohm-meter did not indicate any visible earthing. I tried hard but could not trace the fault physically. I just replaced the fuse. The machine operated without problems for few weeks.

Wonderful!

And then the fuse blew again. Well, I reckoned it could be just a transient phenomenon.

Cleaned up the electrical panel. Replaced the fuse. No problem.

After about 10 days the fuse blew again, followed by tripping of the ELCB.

Now I was getting really mad. Opened up the incoming R-phase cable terminals at both ends (about 4 meters). Checked with a “Neon tester’ and it glowed gracefully. Cable must have got shorted inside. Changed the cable. Replaced the fuse. Now the machine was running perfectly. But strangely there was no tell-tell sign of burn mark in the old cable.

After about a week the drama was repeated. This time, without much ado, I replaced the R phase fuse with a 16A HRC fuse.

After about a week, there was a flash at the incoming terminal box of the drilling machine.

The Fuse blew, ELCB tripped.

But I was more than happy. I had found the culprit. The incoming screw holding the Terminal Block had fouled with the terminal of the R phase.

Another lesson. Neon tester had been showing capacitive voltage.

--- P. K. Ray ----

raynar.industries@gmail.com

Insulation Value Crisis !

2006-11-29T06:28:00.000-08:00

I was looking after the erection and commissioning of electrics at Bhilai Steel Plant (Site : Rajahara Mines) in Central India in the early sixties. Massive construction activity was on. The plant was being set up with the assistance of the erstwhile USSR.

A high-tension slip ring induction motor of 250 KW for driving a cone crusher was to be installed. The standard practice is that the insulation levels are checked and only when the IR (Insulation Resistance) value is more than several Mega ohms, the motor is energised.

On initial checking, the IR value was found to be much less than 1 Mega ohm. This was not considered unusual as the motor was shipped from the USSR long back and during several weeks of transportation and storage, moisture could have seeped in. As a standard remedial measure, the motor was put on heating, initially by external means and later by passing a current in the rotor of value higher than its rated load current. The motor was placed at its final location, which was about 25 meters below the ground level, in a pit. Since it was very cumbersome to get down into the pit every time to measure the IR value, the Meggar was kept at ground level, and a set of cables was sent down into the pit and connected to the motor.

The heating was started and, after every one-hour, the readings were taken. We were surprised to note that the IR value continued to remain low. After several rounds of heating, the result was the same much to the annoyance of the commissioning crew, and adding to the perplexity of the engineers.
Experts from the USSR were also at a loss.

The situation became very critical when it was known that the plant commissioning date was fixed just after 3 days to coincide with the visit of the then minister of Steel and Mines.

After many hours of lost sleep and anxiety of the team, it occurred to me to go down to the pit with the Megger and check the IR value connecting the Megger leads directly to the motor terminals. And lo, the value indicated was more than 100 Mega ohms, which was perfect! The readings were taken many times to ascertain that the values were consistent!

After analysis, it turned out that some one, while searching for a cable of suitable length, found an L.T. 3-core cable lying around, and 2 cores of this cable were used. Since the megger was a 10 kV HT Megger, it was measuring the insulation resistance between two cores of a low-tension cable. Even though the motor at the end of the cable had attained high insulation resistance after heating, the lead insulation itself was much lower and naturally the lower value was being indicated by the Megger. The Megger was measuring the inter-lead insulation and not the motor insulation value.

The team could then energize the electrics successfully and celebrated with a shot of vodka!

-------- Raghavendra Girimaji.

"Kickbacks" of the Electrical kind

2006-07-09T04:26:00.000-07:00

We all know that an “inductor resists change in the current flowing through it”. We also know that when there is a change in the current through an inductor, it gives rise to an inductive kickback. We put freewheeling diodes across dc relay coils or we stick a snubber across ac relay coils and so on.

I realised, with a shock (quite literally), the possible magnitude of this kickback.

In the early part of my career, one of my responsibilities was to test the incoming materials. This included some HT transformers too. One of these had two secondaries, one star connected and the other delta connected. These supplied diode bridges that eventually supplied a twelve-pulse output used as the anode supply in a large RF induction heater.

I was still learning my ropes and I had to test one of these transformers for the first time. I decided to first measure the winding resistances and see I they matched the specifications. I connected the probes of an analog multimeter, set to measure resistance, across the secondary. To make the connections, I held the probes of the multimeter to the terminals by hand. Since the winding inductances were fairly high, the needle started its sluggish motion and I realised that I had set the range wrongly. I removed the probe held in my right hand and I was in for a shock! The small dc current that the meter had already driven into the coil was interrupted and this generated such a kickback that my left hand flew, still holding the probe. That pulled the meter attached to it from its precarious perch on the transformer and sent it crashing to the floor.

So, this is what an inductive kickback “feels” like!

Many would not believe me when I told them this story. However, if I asked them to try it for themselves, there were no takers!

---- JL Anil Kumar.

A delayed “Blast”

2006-07-06T09:14:00.000-07:00

The occasion

Inauguration of the manufacturing facilities for the production of Air Blast Circuit Breaker (ABCB)

Location and time

Central India, Circa 1964

Inauguration by

The then prime minister of India

Background

It was a major event for the plant management. The first ABCB manufactured/assembled at the plant (Technology from UK) was to be inaugurated by pushing a button to actuate the ABCB.

Scenario on the eve

Hectic preparations and trials to ensure that everything goes well without any hitch!

On the D Day

The team of dignitaries was given an overview of the activities. The PM was the requested to push the button; he did so and then ..............................

...Nothing happened!

PM was requested to push it again.....a little harder this time. The result?

Ditto.... nothing happened!

A hush fell over the audience. A red-faced management looked on helplessly not knowing what to do. And then the saving grace! Fortunately the PM was amused instead of getting annoyed.

Everybody heaved a sigh of relief and the event was declared as over. The retinue turned back and started moving towards the exit. AND THEN ..........it happened. There was a BANG and the ABCB operated (apparently) on its own. The team turned back startled to realize that it was indeed the ABCB, which had operated after a delay!

The management felt relieved and that was it.

And now the inside story...

During the last minute checking it had been found that an interlocking relay that was meant to ensure that the air supply to the ABCB was ON prior to the pushing operation, had stopped to function. Therefore, it was arranged to post an employee physically to ensure availability of the air supply. The poor man, who had worked through the numerous trials the previous night, had dozed off at the critical moment and forgot to switch on the air supply. After a late realization that he had goofed up, he acted with great alacrity and switched the supply on which had caused the bang.

( Based on the narration of some of my senior colleagues)

JLAK’s Law of Troubleshooting

2006-06-23T06:45:00.000-07:00

Simply stated, “When a complex system is being troubleshot, an expert in a subsystem always suspects the subsystem he knows least about”.

I arrived at this ‘law’ after repeated observation of this law at play when CNC machine tools were being tested, tuned and qualified. This being a control system with multiple control loops, the effect of one fault would manifest itself in all the variables – jerky motion of the axes, unsteady speed reference to the drive controller, unsteady tacho voltage, unsteady encoder feedback, etc.

This is how the scenario would look:

All the experts have been called because, during the production testing the movement of the axis is found to be uneven and the normal fault tree and troubleshooting chart have not helped.

CNC expert: Have you checked if there is stick-slip? (Being a digital electronics guy he knows a little about the drive electrics. So, he does not question that.)

Drives expert: Are you sure there is no backlash? (Notice that the two suspected causes sound pretty impressive and have a ‘certain something’ (as Asterix would say) about their sound.

The Mechanical expert: Have you tuned the drive?

It would go on and on. Some ‘poor generalist’, who is a down to earth guy, is pottering away at finding the root cause of the problem. Shielding that has come off, a dry solder or whatever would be found and corrected and the system would start behaving itself.

Then all the experts would leave shaking their heads and clucking their tongues muttering “these production guys never do anything right”!

Even in the trivial case of a simple motor controller troubleshooting, the test engineer soldiers on trying to fix the problem all on his own, until he sees a specialist in motors. He immediately starts suspecting all kinds of esoteric problems with the motor. One of the first things the motor man himself would ask is perhaps “is the incoming phase sequence OK?” or “Have you checked the tacho coupling?” – even if the drive is a single phase one or the motor has an integral shaft mounted tacho.-----Contributed by JLAK

A truly "dynamic" issue

2006-06-05T06:18:00.000-07:00

I had been on a servicing trip to a remote part of India. There was this Aluminium rod mill, which had one of our thyristor DC drives. The motor operated at very low speeds most of the time and its speed had started drifting. After some observation, all I had to do was change the operation amplifier on the drive control card and things were back to normal. The customer was very happy. With the traditional Indian hospitality made keener by the remoteness of the place, the customer’s maintenance engineer took me to a nearby dam, one of the largest in the world.

By the time we returned from the trip disaster awaited me. (Incidentally, when we were returning, as we crested a small hillock, the engineer said that there must be problem at the plant as the plant had stopped. I asked how he knew. He said he could not hear the sound of the plant. The sound of the plant? Over the roar of a diesel engine jeep? A kilometre away from the factory? I have never been able to fathom this and the subsequent events did not permit to investigate the issue)

Three semiconductor fuses protecting the thyristors had failed and the mill was at a standstill. The customer was very unhappy and concluded that whatever I had done had caused this disaster. In spite of being tired after the trip to the dam site, I started analysing, testing and troubleshooting late into the evening. After much poring over the drawings, I found that there was a serious flaw in the control logic design of the drive.

The drive had dynamic braking facility and one of its basic requirements had been overlooked. When a motor is running and it has to be stopped quickly, dynamic braking is used. The sequence of events is, open the power contactor connecting the drive to the motor, then and only then close the contactor connecting the motor armature to a bank of high power, low ohmic value resistances. However the designed logic sequence had a flaw and, theoretically, it was possible that once in a while, the dynamic braking contactor could come on before the main contactor had opened. When I discovered this and told the maintenance engineer about it, he would not believe me. His argument was simple. This drive has been working without a problem for the last three years or more. Every shift, we turn this drive off at least twice – once at “lunch time” and once at the end of the shift. The drive works three shifts a day. This means that it is turned off 6 times a day. That means it has been, at the least, turned off two thousand times and this has never happened before.

My arguments about probabilities and the change in the time characteristics of the relays and contacts would not move this man. He did not allow me to change the logic sequence until he was satisfied. I had to set up an experiment to prove that this was happening. I was really worried. What if the rare event does not occur for the next two thousand times?

With no other option, I did set up the experiment and as luck would have it, the fault occurred within a short time and small number of trials. But, you had to carefully observe two sets of lamps. A had to go off before B came on. And the time difference is just a fraction of a second. I saw it and no one else did. After another few trials the maintenance engineer’s assistant saw it but not the big man himself. So it went on and on. And finally, it occurred with such a huge overlap (A and B both on) that the big man himself saw it. And then he granted me the permission to change the logic design. I had to be very careful and finally did the change on paper and executed it in the panel too.

The experiments restarted to make sure that there was no repeat. Thus was solved a tricky problem. It is another matter that I had to wait for days to get the replacement parts as Christmas and New Years day intervened. Finally I got the parts and restored the drive and was allowed to get back home.

--JL Anilkumar

THE MOTOR WHICH REFUSED TO BEHAVE !!!

2006-05-22T06:39:00.000-07:00

About three decades back, immediately on completion of my studies, I joined a major electrical manufacturing company in India. As a part of my training during the first year, I was deputed to a project site where electrics for a rolling mill were being commissioned. I was assigned to a team, which was installing and commissioning control room plenum ventilation system. The system consisted of huge ventilation room which was fed by two large ventilation blowers on the east and west side of the control room (one on either side).

Fresh from the college, I was raring to go to display all my newly acquired (?) knowledge! My task was to assist a team (which basically meant holding the multimeter and megger!).I started my work with great alacrity! After checking up the connections, supply to the three-phase induction motor driving the east side ventilation blower was switched on. The motor started rotating but in the reverse direction! I concluded (and I was very proud of it!) that the connections to the two phases need to be interchanged. We did it at the motor terminals and switched it on. No change in the direction of rotation! I was truly stumped. Were all my fundamentals wrong?
My senior colleague also noticed that the motor was rotating at much smaller speed.(about one-fifth of the synchronous speed).This was another assault on my “fundamentals” since i was taught that under normal conditions an inductions always runs at slightly below the synchronous speed and cannot run at such low speeds.
A great deal of time was spent to find out the problem with no success. The electrical team was under tremendous pressure from the client as the next day was the D-day for commissioning. It was almost the closing time.

All of a sudden one of our colleague came running and wanted to know why the ventilation motor on the west side was running! This was totally unexpected.
Then it dawned on us that when we were switching on (what we thought) the east side motor, actually the west side motor was getting switched on (obviously due to wrong cabling). The air pushed by the west side ventilation motor through the common duct was causing east side blower and hence the motor to rotate at a slow speed.
Of course, once the cause was known, it was easy to set right the things and go ahead with the commissioning the next day.

About Electrical Anecdotes

2006-05-21T04:41:00.000-07:00

As compared to the other branches of engineering such as civil, mechanical, chemical etc., the electrical engineering abounds in abstract/invisible entities like current, flux, power factor, reactive power, charge and so on. This makes their study more frustrating or more fascinating depending on how we were taught! In the initial years of my engineering study, when we were required to study basics of all engineering streams, the electrical subject was voted as most difficult by the students.

However, the point I am now putting forth is, that the testing and commissioning of the electrical systems is more challenging and complex because one cannot see and visualize the happenings as in case of say civil or mechanical engineering projects. Try explaining to a non-electrical person that some electrical actuator operated on its own due to a stray pick-up.

The unique and peculiar nature of this field has led to sometimes amusing situations in the course of my practice. I am sure, many of us would have come across puzzling and intriguing situations and successfully got over it. Therefore it struck me that it would be great to create a forum where fellow professionals can share such anecdotes/experiences. Apart from being interesting, it could prove useful too!

I welcome you to go ahead and start mailing your experiences in brief to me at nagrajrao@ieee.org, and I will post it on this web site.