- ... A photo of the similar 505D L3 2 motor power plant is in the group s photos:Message 1 of 5 , Aug 1, 2011View Source--- In firstname.lastname@example.org, "widebandit" <widebandit@...> wrote:
>A photo of the similar 505D L3 2 motor power plant is in the group's photos:
> TD2 only needed single-phase...
> So a TH station used from four to seven motor alternators to supply the necessary firm AC to radio bays and FM terminals...
> The 508A motor-alternator set was a fairly sophisticated unit...
> The AC motor and alternator were both brushless...
> Alternator was self-exciting with on-rotor rectifiers...
> At start-up the AC motor ran as a simple squirrel cage induction motor; internal flux pathways were designed into the rotor so that as it came up to speed it would "pull into" synchronous rotation...
> There was also a DC motor on the same shaft...
> When AC power failed the DC motor took the load until station generators fired up and came on-line...
> The DC brushes were lifted by solenoids to eliminate wear until they were needed. When commercial AC failed, the solenoids dropped the brushes onto the commutator; taking DC current from 130V station battery plant...
Later TH stations had the much smaller & efficient 508H(?) solid state converters.I don't recall whether they required 3 phase inputs or not.
- ... Wow; SWER is not common in the US. Did everything in TD2 run off of battery plant directly? ...Message 2 of 5 , Aug 1, 2011View SourceOn 8/1/11 1:31 AM, widebandit wrote:
> Some TD2 sites way out in the boonies - like Cutter New Mexico - were fed by a single wire(!)...Wow; SWER <https://secure.wikimedia.org/wikipedia/en/wiki/SWER> is not
common in the US.
Did everything in TD2 run off of battery plant directly?
> TH radio (BSTJ November 1961) used three-phase power to run synchronous motor-alternators...<http://www.alcatel-lucent.com/bstj/vol40-1961/articles/bstj40-6-1627.pdf>
is an interesting read.
I have no idea how the synchronous motor with no excitation works. It's
common to start a synchronous motor via induction, then apply excitation.
The self-excited generator is now pretty common.
The dual motor scheme is an old idea; I recall a pipeline firepump with AC
and diesel powerplants straddling the pump.
> With TH radio, the decision was made to feed the bays with "firm AC" and derive necessary DC potentials locally...Note the 508A had a fair-sized flywheel; clearly that was an important
aspect of the design. A large flywheel was a good filter, and bridged the
spikes of going from one power source to the other.
Note many ISP's are using a similar scheme; HiTek units are used at some
carrier hotels [hosting sites...]. They last long enough for the Diesel to
start & get to speed.
I see mention of L-carrier in the above; so coax undergrounds used 508A's