Hand Cranked vs Digital Transformer Turns Ratio

[olicg]

Hi,

I would like to know the relative advantages / disadv of hand cranked v Digital TTR sets available from various vendors.

Any document would be of real help. Reply with points is also appreciated.

Thanks in Advance,
Olicg

 

[DanDel]

The main difference I notice is that the battery-operated digital unit we use sometimes (AEMC 8500; 1-phase) gives incorrect data for larger units, because it doesn't have enough power output. A larger 3-phase unit works fine, but it has an AC power cord.
Obviously, the digital unit is easier to use in most instances.
The hand-crank units (Biddle 55003, 550005), while taking longer to get the results, and requiring a little more knowledge and technique, have never let me down with accuracy or dead batteries.

 

[wbd]

Plus you get a little workout to count towards your fitness program.

 

[unclebob]

Well an obvious advantage for the hand cranked: no AC power needed.

 

[oldfieldguy]

In my experience, the hand-cranked units are more forgiving of differences in size and will still be serviceable after a technician makes a mistake in connection. They require a better understanding of the phase relationships between windings. I learned these things with a Biddle "coffee-grinder".

The electronic units are fun to play with, and properly used, can be faster, but it is not unusual to find results which don't match expectations, and the electronic units I've used don't seem to have the "oomph" to work in some situations.

old field guy

 

[olicg]

This is quite interesting. Views from field guys show that they have more FAITH in hand cranked units. Interesting or rather striking thing is that even with advancement of digital technology, there are instruments from older days still preferable and mainly because of higher reliability and accuracy!

I would rather like someone to give positive remarks on digital units also.

Regards,
Olic

 

[oldfieldguy]

olic--

I guess the best way to put it is that when one has the electronic, digitalized unit, MOST of the time one can get accurate results faster and often with less training.

However, there are situations wherein the electronic unit may not work, and in that case the old coffee-grinder will likely give good results.

If I had a bunch of transformers to test, I would likely head out the door with the electronic unit, but I'd like to know that if things went south with it, I could still find the coffee-grinder on the shelf.

old field guy

 

[able357]

I use a digital turns ratio test set. If you are looking for accuracy its more dependable or accurate. If your upper and lower limits are like 5% then the digital set will have more resolution also.

 

[olicg]

I am interested in knowing the exact technical limitations of digital TTR sets. What specifications i should ask for when i want to test 1 MVA to 500 MVA power transformers from 3.3 KV voltage upto 500 KV.

 

[able357]

Well, when you look at testing a transformer and getting its turns ratio your inputting a voltage and reading it back on the other end. So your question is what specifications should you ask for? Any ratio bridge should be fine, if you put in 100 volts or a 1000 volts your ratio should stay the same! One thing you do have to remmeber about is the phase displacement, some bridges only test at 30° displacements...If you need to test systems that have less displacements such as 15° or 7.5° then you will need to specify that. I go through raytech.com they are excellent and build the software according to your hardware and software specs!