Hi There I have been trying to find some experts in this area of what is the correct method of determining if a DC drive is 6 or 12 pulse, I was told that the criteria was how many pulses in one sign wave is the determining factor but where do you look for or measure that with a scope. The amount of SCRs is a clue but it has to do with firing board timing. maybe one of you experts can give a short list of 6 and 12 pulse drives that are common in the us. Allan bradley,megatec,Kone,Armor,Louis allis,Baldor,Valutrol ect, also what is this IEEE519 I keep hearing about. Thanks Jim

-- jim (elevator555@hotmail.com), December 02, 2003

Answers

Jim:

Regarding ANSI/IEEE 519, it refers to the IEEE Recommended Practices and Requirements for Harmonic Control In Electric Power Systems. Basically, it lists recommended limits for total current and voltage harmonic distortions in an electrical distribution system at the point of common coupling. This point of common coupling is the point between the non-linear load and its connection to a power source.

-- Chris Maida (sales@vacontrols.com), December 03, 2003.

Listen to the 'hum'. If it is 360 Hz, it a 6-pulse drive. If its 720 Hz, its a 12 pulse. (60 Hz utility power)

If you have an oscilloscope you can also look at the voltage waveform being fed to the motor. Count the peaks for a given period of time. 6 pulses in 16.7 mSec = 6-pulse. 12 pulses in 16.7 mSec = 12-pulse.

Look at the transformer. If there are 2 heafty secondary windings its probably a 12-pulse drive.

Most SCR DC drives are 6-pulse. MCE makes their own 12-pulse SCR drive and is about the only one available in North America.

DonV

-- Don Vollrath (dvollrath@magnetek.com), December 03, 2003.

Hi There Thanks for the answer from both Chris and Don, very good I will check that with a scope first chance I get, Hey Don how about Kone 9000 SCD drives, they are pretty quiet and does magnetec make a 12 pulse. Thanks Jim

-- Jim (elevator555@hotmail.com), December 04, 2003.

I'm not familiar directly with the KONE SCD drive. One version (not in current production) was 6-pulse. In North America the KONE DC drives are furnished by Rockwell/A-B & they are 6-pulse. A 6-pulse drive usually has a rather large inductor/filter between drive & DC motor to reduce acoustic noise. A 12-pulse drive has much smaller filter components.

Magnetek does not make a 12-pulse SCR drive.

-- Don Vollrath (dvollrath@magnetek.com), December 30, 2003.

Jim, You could look at the input terminals of the drive. The 6 pulse has 3 terminals while the 12 pulse needs 6 terminals due to voltage phase shift. Benjamin

-- Benjamin (bat1888@msn.com), May 04, 2004.

FYI - AB/Rockwell is delivering an 18 pulse drive at or less cost than the 12 pulse drives. They offer this to insure the IEEE spec. and some componants are less expensive. It is difficult to analyse the distortion at the common coupling without time, equipment and proper testing. There are load requirements required where facilities can't do to achieve a proper static test let alone a period test. Most instances are calculated tests with only xformer information and estimated loads. 18 pulse drives are working well at IBM and Dartmouth college.

-- Richard Battis (rbattis@lavalleys.com), December 14, 2004.