Rotary Conveter on AM

AM Radio discussion. Directional arrays are FUN!
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rich wood
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Rotary Conveter on AM

Post by rich wood » Fri Feb 12, 2016 4:07 pm

Hello to All,
I have a project in the works for a new high power AM system, but the three phase power is $200,000 away from the site. Does anyone have experience with a rotary phase converter on an AM transmitter. I have used them on FM's and they provide a constant load, verses the current shift with modulation of an AM.
I really want to stay away from an open delta feed system for "making" the third phase.
Thanks

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Deep Thought
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Re: Rotary Conveter on AM

Post by Deep Thought » Fri Feb 12, 2016 4:12 pm

I've seen them used up to 25 KW. They generally aren't happy with an AM load but do work. You'll have to over-spec it. What's the TPO and the AC load?
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

rich wood
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Re: Rotary Conveter on AM

Post by rich wood » Fri Feb 12, 2016 4:17 pm

DT,
The AM is a 25 kW and with the tower lights and HVAC the site would pull around 100 kVA.

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Deep Thought
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Re: Rotary Conveter on AM

Post by Deep Thought » Fri Feb 12, 2016 5:11 pm

Last one of these I was involved in ended up with 800 amp single-phase 240 volt service but I am not sure how the power company and electrician arrived at that figure. This is a 25 KW Nautel ND-25 "Ampfet" solid state transmitter, and at the full 25 KW with no modulation the transmitter/rotary converter combination drew 31 KW. Under modulation conditions it groaned a lot and we sometimes had issues with positive peak modulation sags running tones, but this station is mostly talk and gospel music so it doesn't get pushed too hard. Hopefully you can work from that.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

RodeoJack
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Re: Rotary Conveter on AM

Post by RodeoJack » Sat Feb 13, 2016 5:00 am

Years ago (like 32), I did this with a Phasemaster and a 5kW ITA. I think the best we had then was a BL-40 Modulimiter, and that transmitter didn't much like positives anyway... so we didn't try.

I was expecting something in there to complain, but given what we had to work with and the fact we didn't push it very hard, it actually worked pretty well.

rfn
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Re: Rotary Conveter on AM

Post by rfn » Sat Feb 13, 2016 8:05 pm

Deep Thought, please check your private messages about an ND-25 issue that is off-topic for this thread but could save you a lot of work. Not of general enough interest to start a new thread.

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