Al the man

[krymis]

Al,

I was still trying to figure out why my IH power supply would have 2 bridge rectifiers. They are Taiwan Semiconductor Model# GPBC3502 and have a 603 AC over on the other end of the same side. What would be the purpose of this? There is only on set of taps coming off of the transformer, and the wires coming off of the taps are split into 2 and shared between the rectifiers. Oh and any more info that can help me understand this would be greatly appreciated.

I also found that the Bleeder resistor is a CMS-20????. It looks like it says 750ohms but I did not see them listed on the net anywhere. Would it be acceptable to use a resistor with a 2k ohm rating in its place?

Thank you for all your help. I have learned a great deal in researching this stuff.

[Al_The_Man]

Is there only one secondary and two bridge rectifiers connected to the same winding?
is there two separate DC power supply?
Al.

[krymis]

nope. its just one transformer one set of taps is on one side for the 120v in and the other set of taps is connected to the two bridge rectifiers. That is why i am having a hard time figuring out this particular power supply. THe rectifier on the left has the + left open and the - goes to the - of the cap. the rectifier on the right has the - left open and the + goes to the + of the cap.

Also is that CMS20-2kohm ok to use as a bleeder as i can not find a 750ohm one?

[pastera]

If you use only half the bridge, each device dissipates half the power - can be less expensive to use two smaller parts than one large part.

bridge is a 200 volt 35 amp part - $2.76
The cheapest 70+ amp part I saw with a quick search was >$20


Aaron

[Al_The_Man]

With only one DC supply source, it Doesn't seem to make much sense? It appears from that they are using one half of each bridge?
Al.

[krymis]

Aaron,

Would I happen to have talked to you on the phone at some point? I may be wrong on this one.

Anyways, why would digikey have a 35A 1000V rectifier for 6.50? Has the price come down that far? I mean it makes scense that they would do that but how much are they really saving after adding in the connectors and wire and the time for the second set of lines? Plus wouldn't you want a smaller footprint? I mean I am trying to figure out why use a second one and everyone says just use one. I may be off on this a little. Pastera if you could give me anymore insite to this idea it would be awesome. I am trying to understand why manufacturers deviate from the norm. Maybe you and Al can get me upto speed on what is going on. I believe that using one is the way i will go but I would still like the knowledge.

Also why look for a 70A rectifier when i am only jumping it to 20A? Does it matter if I am using the transformer type there instead of a toroid? What is the type of transformer used here? is it a laminated core?

[Al_The_Man]

Originally Posted by krymis I may be off on this a little. Pastera if you could give me anymore insite to this idea it would be awesome. I am trying to understand why manufacturers deviate from the norm. Maybe you and Al can get me upto speed on what is going on. I believe that using one is the way i will go but I would still like the knowledge. Also why look for a 70A rectifier when i am only jumping it to 20A? Does it matter if I am using the transformer type there instead of a toroid? What is the type of transformer used here? is it a laminated core?

Maybe cost saving was the criteria here, but for a manufacturer to do this seems rather chinzy!
A four diode stud setup would probably have been cheaper.
The transformer is a Laminated EI core.
Both types work for what you want, it is just the Toroids are a little more efficient but often cost more, the up side is they can be modified fairly easily, turns put on/taken off or extra secondary etc.
Al.

[vger]

Krymis,
Looking at the first picture you posted, it appears that there are mounting holes in the chassis for an additional cap there between the exixting cap and the fuse. Perhaps they offer the same supply with 2 caps using the other 2 terminals on the bridges?
Steve

[krymis]

that is another great point. I never would have thought of that either.

[GeneK]

Originally Posted by vger Krymis, Looking at the first picture you posted, it appears that there are mounting holes in the chassis for an additional cap there between the exixting cap and the fuse. Perhaps they offer the same supply with 2 caps using the other 2 terminals on the bridges? Steve

It's been a while since I did any electronics design but I would probably do it this way for heat disapation, each rectifier is sinking only half as much heat to the base plate. That means there is twice as much area to take the heat out of the devices.

GeneK

[krymis]

man i just keep getting impressed with the answers to this and many other questions.