Condenser fan motor sustitute

Martin Eastburn wrote:


Martin, most new broadcast transmitters are all solid state. The last tube final transmitter I maintained used three 65 KW EEV Klystrons for a 5 MW EIRP output on NTSC TV ch. 55 with the antenna on a 1700' tower. It was a Comark, and was built around 1985. It was water cooled, along with the smaller RCA TTU25B that I used to build WMRX ch. 58 in Destin Florida.
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Those are small. But almost reasonable for a home rig :-)
Consider those that drive the largest phase array radar in the world ? How about those that drive the CERN toys.
Some of the 3' and 6' are used on linear accelerators to make radioactive isotopes for treatments and machines.
Then there are those along the long SLAC that drives beams near the speed of light. Big stuff.
The largest ones - the base commander had a pair placed at the front gate like missiles. Seems the maker, a large mil company, got the mechanical specs inside off. They were to big to ship back and the plant used them as stick in the eye of the local rep every day. No longer there and the plant outside area is a bit different.
You know they are big when you can unbolt the side plate to replace the filament. Naturally you are in a hard RAD suit at the time.
Martin
On 8/22/2015 9:08 PM, Michael A. Terrell wrote:

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On 8/18/2015 9:18 AM, Michael A. Terrell wrote:

For the time machine?
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Tom Gardner wrote:

No, for the chroma circuit on every cheap assed tube type color TV. You could find up to seven bad tubes in a single TV. :(
The time machine used a Z80B. ;-)
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On 2015-08-18, Lloyd E. Sponenburgh <lloydspinsidemindspring.com> wrote:

    And, depending on the failure mode, it can make diagnosis a bit more complex. Mine, when it failed, had the connection of the common of the two caps to the common output terminal open, so in effect there was a smaller value cap between the two load points. That was enough to start the fan (with the compressor acting as a virtual ground), but far too small to start the compressor, so it kept cycling, with the current limit opening and then re-closing a few minutes later, resulting in a repeated dimming of lights. And, when it tried to check it, it appeared that the cap was good. :-)

    Those would be the electrolytic caps, no doubt. (Mostly power filter after rectifiers.) They had the common ground in the metal case, and could benefit from the lowered cost of manufacture -- and the lowered cost of mounting components.
    Enjoy,         DoN.
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On 08/18/2015 08:43 PM, DoN. Nichols wrote:

The failure mode in mine has always been that the compressor cap blows and causes the lid to dome upward, breaking the internal connection to the fan cap. What makes it interesting is that I have a "hard start kit" installed, and that's enough to get the compressor started. The fan won't start without it's cap, so the compressor cycles on the high pressure limit switch. I wish it would just lock itself out instead of cycling that way repeatedly.
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On 8/18/2015 6:49 AM, Lloyd E. Sponenburgh wrote:

With the dual caps, if one blows it rips the connection loose for the other thus your pump stops if the fan cap blows. How can you duplicate that protection?
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Tom, they most often fail by another mechanism. Most often, they just lose capacity until they no longer will start their associated motor.
That "protection" is accidental, anyway. "Blowing" is less often seen than just "venting", and they don't tear themselves apart mechanically when they vent.
Adding protection for a bad compressor start would be easy enough... when they don't start, they kick their over-temp switch, and that signal could be used to turn off a latching relay on the fan circuit.
Adding protection in the opposite case would be harder, since most fan motors are just split-phase induction motors, and if they have any thermal protection at all, it's internal. You'd have to add some sort of 'air motion sensing' to manage that one.
Lloyd
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Actually the start cap if dry won't start the motor well. The cap is in series with the start winding and a switch. There is enough working to start a slow ramp up to speed and once there have power.
The start cap is a reactive negative resistance to the coil's positive resistance. (reactance really). A tug on a rope start and it will turn over faster and catch.
Some caps have fuses in then - to protect the motor if the cap shorts. Martin
On 8/21/2015 9:43 AM, Lloyd E. Sponenburgh wrote:

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On 08/21/2015 09:43 AM, Lloyd E. Sponenburgh wrote:

Who cares whether the fan runs all by itself? That won't hurt anything. What would be nice would be for the compressor to lock itself out rather than keep cycling on its over-temp limit.
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Bob Nichols AT comcast.net I am "RNichols42"

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On Fri, 21 Aug 2015 23:20:48 -0500, Robert Nichols

Exactly, Bob. That's what scared me when mine died. I did NOT want to lose that pump!
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Yes we know two with one blow. However both are by the same guy that made them with faulty paper or seals. So both are in the trash.
It is for design and space. Often in designs you will see duals and triples making pi or L filters and power supply brute force filters. Martin
On 8/21/2015 9:22 AM, Tom Gardner wrote:

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On 08/18/2015 12:23 AM, Tom Gardner wrote:

Certainly, you can. You just need another wire to connect the common terminal of the two caps together. But you might not find it easy to get capacitors of those values with voltage ratings much higher than the 440V of the ones you have now. And yes, it does need to be that high even for a 240V supply. I measure 425V across the run cap for my compressor. I'm sure it spikes higher than that during power "events".
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    Sure you can. They have a common point to which one side of both caps are connected, and then the free end of each goes off to the appropriate load. (The larger one to the compressor, the smaller to the fan.)
    For that matter -- the caps in my unit were replaced by a special "replacement" cap which was in reality six caps of different values, all connected to the one common, and the free end brought out to a number of terminals. In practice, one was the right value to run the fan, and all the rest in parallel added up to the value needed for the compressor. (For those who don't know, capacitors in parallel add, resistors in parallel produce a lower value. If only two, and both are the same value, the result is half the value. If different values, or a number in parallel, the math is a little more complex. Divide each value into 1, add the results together, and then divide that value into 1 to get the result. Something similar is done for caps in series.
    Enjoy,         DoN.
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As many others have said, yes you can, and it's often a good idea.
Also, capacitor makers differ in how much safety margin they build in, so buy only from the better brands.
Joe Gwinn
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On Tuesday, August 11, 2015 at 7:55:40 AM UTC-7, stryped wrote:

The starting current might go up (so it behooves you to check the ratings of whatever relay or contactor drives this motor), but operating current will be about the same (because you aren't changing the mechanical load). So, substitute away!
1100 RPM is kinda oddball, but a web search finds the part; Amazon and other suppliers will sell you an identical replacement part, it seems.
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Not to Stryped. He doesn't LOOK for parts before he asks here to get help finding the parts he never looked for... Heck, he doesn't look for _any_ information before he asks here.
And with deference to you (few) guys who actually know what you're doing, this is the LAST place anyone should ask for good, sound mechanical advice!
Lloyd
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On Tuesday, August 11, 2015 at 10:55:40 AM UTC-4, stryped wrote:

http://www.southernwinding.com/
Try those folks. I've had very good service from them over the years with small motor rewinds.
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