Summary for rectifier ripple Discussion
rectifier ripple is the main concern in this thread, where Joy Banerjee asks how to check ripple in a 12 V, 4000 A rectifier and what ripple level is acceptable for chrome-nickel plating. Ted Mooney answers that ripple can be measured with a ripple meter that compares AC to DC, and says most people consider about 5% ripple close enough for nickel and chrome plating. He adds that a properly functioning 3-phase rectifier should produce only about 5% ripple at full rating, but at reduced output the SCR waveform can become “shark fins,” increasing ripple and possibly requiring a filter choke. Gurvin Singh adds that ripple can also be observed with an oscilloscope, AC power analyzer, data logger, or a true RMS multimeter, noting that a true RMS meter is the fastest and cheapest practical check. In a later question, Ted asks the reader to restate the inquiry based on the earlier 5% guidance.
Q. Dear Sir:
I want to check the ripple contents in my 12 Volts and 4000 Amps rectifiers. Can you help me? Also what should be the ripple contents in the chrome-nickel plating. Waiting for response
Thanks,
JOY BANERJEE
a rectifier company – FARIDABAD, India
2003
A. You can check ripple with a ripple meter which measures AC and compares it to DC. Most people usually think 5% ripple is close enough for nickel and chrome plating.
Although a properly functioning 3-phase rectifier will automatically produce only 5 percent ripple–that is at full rating, when the input current is coming in as an AC sine wave. If you are operating at reduced output, so your SCRs are outputting shark fins instead of sine waves, your ripple may be much higher and you probably will need a filter choke.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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Q. Dear Sir,
Thanks for the reply. But please let me know what will be the ripple content of a hexa phase rectification by using Silicon Power diodes and the voltage being controlled by an linearly variable Auto transformer. Also let us know what will be the effect of the voltage variation on the ripples and the efficiency of the rectifier (12 V/4000 Amps). Waiting for your reply.
With regards,
Joy Banerjee [returning]
– Faridabad
2003
A. My understanding, from looking at the voltage profile of hexa phase-rectification, is that the ripple at full output will be under 5 percent. Please see letter 1424 for more detail. With an autotransformer rectifier, there is no chopping of the incoming voltage as there is in an SCR rectifier, and I believe the ripple will therefore remain at 5 percent at lower output.
You’re the rectifier specialist, not me, Mr. Banerjee, so you’ll have to tell us what efficiency you predict based on the windings, the size of the core, whether you use copper or aluminum, and a bunch of other factors. My understanding as a user, not a rectifier designer, is that rectifiers range from about 70 percent to about 90 percent efficiency.
Ted Mooney, P.E.
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finishing.com – Pine Beach, New Jersey
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A. You can use a large number of tools to actually see the ripple content. I cannot answer what is good or bad. But you can see the ripple. You can use an oscilloscope, AC power analyser or a data logger. There are many suppliers for oscilloscopes including Tektronics, HP, Fluke etc. For AC power analyser you can go for Fluke. For data-logger you can use true RMS meter and the wave form can be seen on a computer. A good quality true RMS multimeter used to check AC voltage on DC will give you very good idea of the ripple content. This is the fastest and cheapest method to check for ripple.
The ripple is the AC component of DC so you need AC measuring equipment, so do not get confused on the recommendation of AC power analyser!
Gurvin Singh
Mohali, Punjab, India
2003
Q. Dear sir
I want know how much ripple contents are in the different type of silicon rectifier with different connections.
3-phase rectifiers for the Electroplating and for the other processes.
So please give us the complete information of as per the connection.
Thanks
Kunal Gautam
electric and machinery – Ludhiana, Punjab, India
March 31, 2010
A. Hi, Kunal. We’ve already answered 5 percent and explained why, and explained the procedures for checking it. So, unfortunately, I’m not quite understanding the question. Could you please review letter 1424 and phrase your inquiry in terms of what has already been said? Thanks!
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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Q. I have a Nickel Tank 250 L. The rectifier has a capacity of 25V, 150 A. When I check the ripple, let’s say @5V DC= 5.3 AC= 6.1 (1). That doesn’t make any sense. Does anyone have any idea why this happens?
Peter Corona
– Mexico, Jalisco
January 23, 2018