Rectifier wiring

variable

Two can go on one heatsink, but the other two need a heatsink each, or, you will have to ensure you are electrically isolating them from the heatsink. The actual wiring is trivial - just a bridge, however the output voltage is too high for a 100 VDC motor. You will need to simulate the SCR speed control -- or buy a new one. What make was it?

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NTE, There are 2 terminals, how do I connect the AC and DC output?

Search for "bridge rectifier".

I have this rectifier: GPBC 50A

It has four terminals, but they are not marked. The datasheet is pretty sparse, too. Which of them are AC and which are DC?

You can figger it out in a minute or two with your DMM.

Put your multimeter in 'junction test' continuity mode. (Normally indicated by a diode symbol.) Test across every terminal combination of both polarities until you locate the diodes as they conduct in forward direction (Red + to Anode, Black - to Cathode) and as they block in reverse direction (Red + to Cathode, Black - to Anode). Write down each reading on a large sketch of the part and all will be revealed.

It'll prolly end up looking a lot like:

--Winston

Usually the clipped corner (or terminal that is not oriented the same as the other 3) is the positive & the diagonal opposite is negative. The other 2 are the AC.

MikeB

The one on the chamfered corner that's at 90° to the rest is the +, the one _diaagonally_ opposite is the -, and the other two are the AC input terminals.

Check it on 12VDC with a small light bulb in series to be sure. You should measure 11VDC or so out with the + terminal as I said, regardless of the polarity of the input (and, of course, the series light should never light up (!)).

As Ned said, this is easily figured out with a DMM that has a diode check range, but compare it with a regular diode to be sure of the polarity. Most digital DMMs have the red lead source positive voltage, and most analog VOMs are the opposite.

Obviously if you get it wrong you'll probably kill the bridge or cause the capacitor to vent its lifeblood.

Best regards, Spehro Pefhany

The GBPC case seems to use the angled corner as the + indicator. See this datasheet:

John

Ignoramus14602 fired this volley in news:7NSdneQgVuYjvLDRnZ2dnUVZ snipped-for-privacy@giganews.com:

They ARE marked, Iggy. The corner miter usually denotes the + output lead.

LLoyd

Have you looked on the *top* of the case?

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You guys are taking all the excitement out of Iggy's life. Just hook it up, the smoke will come out if its wrong, then do something else. Like the time I tried a start cap in the run cap position on my three phase converter. Now, I know the difference.

Karl

I figured it out. Thanks to all. The power supply is now working nicely.

I know the fun feeling. In about 0.1 seconds after a loud BANG I know that something went very wrong.

Use your ohm meter to check the polarity of the 4 diodes. The AC goes to the points where the positive and negative diodes join. You get DC+ where the 2 positive diodes joinn, and DC- whre the negative diodes join. GENERALLY the cut off corner, if present, is one of the DC terminals.

The terminal nearest the corner which is cut off is the positive output. (Also, it is at right angles to the other three) The diagonally opposite one is the negative. The other two are AC input.

You can verify this with a multimeter in the ohms or the diode-check positions. Positive probe on the negative terminal will show conduction to the other two adjacent terminals. Negative probe on the Positive terminal will show conduction to the other two adjacent terminals.

The diodes are arranged pretty much like the schematic symbol for a bridge rectifier, and surround the center mounting hole as shown here. Always positive and negative are opposite corners, and the AC inputs are the other two corners. Something will mark the positive terminal as different -- here the cut corner and the blade being at right angles to the rest of the blades. Sometimes there is a red dot by the positive terminal, black near the negative (except on black potting epoxy), and yellow on the two AC inputs.

I guess that they did not spell this out on the data sheet because it is so common a construction -- and has been for at least forty years or so. Or -- it might be spelled out somewhere else in the Comchip products manual -- and you only have two pages out of that manual.

Enjoy, DoN.

I did that once; KaBang it went.

Da KaBang I can handle, it's cleaning up the mess afterwards that is a PITA!

Are you talking about the mess in your shorts?

Karl