rectifier - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: May 08, 2014, 12:05:33 pm
content: dose any one know anything about this component : auxiliary selenium rectifier automat type mv412: mlr selenium rectifier automat type 25zb251: main silicone rectifier ae1 gp6e20pif any one knows or has any info it would very very useful

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 08, 2014, 12:36:25 pm
content: It is not clear what you are asking?If you want to know about selenium rectifiers in general:http://en.wikipedia.org/wiki/Selenium_rectifierSince they are obsolete for many years, finding information (such as electrical specifications) for particular components is probably impossible.If you are trying to replace a selenium rectifier in a circuit, you will probably need to analyze the circuit to derive the voltage and current specifications.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: May 08, 2014, 12:54:02 pm
content: Quote from: Richard Crowley on May 08, 2014, 12:36:25 pmthe name is the part number of a London underground power supply system. if a schematic will help i will post it

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 08, 2014, 01:21:20 pm
content: Yes, a schematic diagram will be very helpful.But please, also tell us what you are trying to do?Are you just collecting historical information?Are you trying to repair or upgrade some piece of gear?

author: liquibyte
author_rank: Frequent Contributor
timestamp: May 08, 2014, 01:25:08 pm
content: Quote from: abdullahseba on May 08, 2014, 12:54:02 pmThis question and subject matter coming from someone with this particular choice of user name strikes me as odd and has probably put you on several watch lists.

author: madshaman
author_rank: Frequent Contributor
timestamp: May 08, 2014, 01:32:00 pm
content: What is wrong with the OP's question? Perhaps they work somewhere where this thing is and are curious about it..

author: abdullahseba
author_rank: Frequent Contributor
timestamp: May 08, 2014, 03:47:26 pm
content: Quote from: madshaman on May 08, 2014, 01:32:00 pmyour right is at that museum at the end of this post

author: abdullahseba
author_rank: Frequent Contributor
timestamp: May 08, 2014, 03:59:04 pm
content: Quote from: Richard Crowley on May 08, 2014, 01:21:20 pmwe are trying to find out the amps that the train requires. the transformer was on the second carriage which we don'thave. by knowing the amps of the rectifier we could make a new onehere is the link for the schematichttp://1drv.ms/1is8UjOits in two parts just click the next button & zoom in

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 08, 2014, 06:35:29 pm
content: Do you mean that you don't have the original power supply? Or do you mean that you don't have the "load" (the second carriage)?It is helpful to see the original power supply. To see the size of the transformer, the gauge of the wiring, the ratings of the other components to help make an educated guess about the current (assuming the voltage can be calculated from the transformer specs, etc.)If you don't have the original power supply, then it is customary to arrange for a temporary power supply: a "bench supply", or in your case, maybe a big pile of heavy batteries of the proper voltage output. Then you can place an amp-meter in series to actually measure the load.Or you may be able to calculate the load. For example, if it is all the lighting in the carriage, you can calculate each lamp, and multiply by the number of lamps, etc.But if the load is some big solenoid or relay, or the brakes, or something, then you don't have much choice but to actually measure the load directly using a temporary supply.Or, you could simply over-specify the replacement. 50A or even 100A diodes are not all that outrageous.Remember, however, that those old selenium rectifiers were nowhere near as efficient as modern silicon diodes, so you may get a higher output voltage than the original.We sometimes must insert heavy series resistors to "simulate" the voltage drop across the old selenium rectifiers.

author: madshaman
author_rank: Frequent Contributor
timestamp: May 08, 2014, 06:43:07 pm
content: Quote from: Richard Crowley on May 08, 2014, 06:35:29 pmPlease reconsider the advice of putting an ammeter in series with an enormous motor...I wouldn't dare do that even with my car's starter.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 08, 2014, 07:12:55 pm
content: Quote from: madshaman on May 08, 2014, 06:43:07 pmOh, absolutely. Agree 127%But if this is running through some smallish selenium rectifier, it seems extraordinarily unlikely that we are even talking about 10-20 amps.I don't think they ever made selenium rectifiers for huge current ratings.Of course, there are heavy shunts that are used to measure large currents (even 100s of amps).Proper use of shunts like that don't alter the underlying safety of the circuit/experiment.But we don't have enough detail about the situation here to make any judgement one way or the other.

author: madshaman
author_rank: Frequent Contributor
timestamp: May 08, 2014, 08:09:18 pm
content: Quote from: Richard Crowley on May 08, 2014, 07:12:55 pmI see your point wrt the rectifier as iirc selenium diodes have a goodly resistance and this may have limited current; I was assuming the old rectifier wasn't going to be involved.Wrt current measurement: You mean something like this? :-)It can handle 300A up to 50KHz.[edit: corrected specs]

author: G7PSK
author_rank: Super Contributor
timestamp: May 09, 2014, 12:46:05 pm
content: Those rectifiers look like they are in the regulation circuit for a rotary converter rather than providing DC to run a motor, the field current will only be a few amps at most.

author: Andy Watson
author_rank: Super Contributor
timestamp: May 09, 2014, 01:23:50 pm
content: The voltages are given on the transformer windings - assuming there's no other external input.If you have access to the original rectifier this document might put you in the right ball-park with regard to current/power handling:http://www.gdrectifiers.co.uk/uploads/Selenium_Rectifiers.pdf

author: abdullahseba
author_rank: Frequent Contributor
timestamp: May 11, 2014, 08:19:04 am
content: Quote from: Richard Crowley on May 08, 2014, 06:35:29 pmwe don`t have the original power supply as it was in the second carriage but adding up the load is a good idea

author: IanB
author_rank: Super Contributor
timestamp: May 11, 2014, 08:34:49 am
content: I believe that at the museum referenced they have one car of ex-Victoria Line 1967 stock, which they have saved for preservation.The London Underground runs on a traction supply of 630 V DC. Since this is inconvenient for lighting and ancillary services on the train, the trains of that era used a motor-alternator set to generate low voltage AC to power such services. I don't know exactly what the voltage would have been, but I think it quite likely it would be 120 V. I am sure some Internet searching is likely to turn up all sorts of technical information about the trains, or failing that some questions may be asked on an Underground related forum (District Dave's would be a start). If there was a transformer, it would have been a step-down transformer powered from the motor-alternator supply.I had a brief look at the uploaded schematics, but I didn't have time to really examine them.

author: Fank1
author_rank: Regular Contributor
timestamp: May 12, 2014, 01:34:03 am
content: What is the physical size of the rectifier plates?I never saw Selenium's used for huge currents.What size wire is going to them?