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G8MNY > TECH 06.08.08 01:01l 49 Lines 2222 Bytes #999 (0) @ WW
BID : 64516_GB7CIP
Read: GUEST
Subj: Power Factor of Drake L-4B PA
Path: IZ3LSV<IK2XDE<DB0RES<ON0AR<GB7CIP
Sent: 080805/2122Z @:GB7CIP.#32.GBR.EU #:64516 [Caterham] $:64516_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New Jul 07)
(8 Bit ASCII Graphics use code page 437 or 850)
For /P work this USA made Drake PA has a very poor mains power factor, on 50Hz
it is only 0.5, this means in standby it draws 2x the mains current it needs
to.
Exactly where to put a PF correction capacitor is not straight forward, as the
PA has Tune & SSB mode where the mains tap on the HT transformer is changed by
30%.
CW/tune
LÄo-oÄÄÄo/oÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ\ oÄÄÄÄÄÄÄÄÄÄÄ¿_
Fuse 1 on ³ oSSB __)|| _
³ ³ TUNE³__ ||(
³____ __ ³_____________)||(
110V)||(__ 6.3V | ³__ ||( 850V TUNE
Heaters, Fan ____)||(__ 30A | )||( or 1.1kV
& Relay PS ³____ || __ | 110V)||( SSB @ 2A
Transformer ³110V)||( 20V | _____)||( to the
FAN )||(__0.5A | [o-o__ ||( Voltage
ÃÄÄÄÄÙ 16uF=== Fuse 2 )||( Doubler
³ 250V| 110V)||(_
³ AC | _)||
NÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ 2kW Peak HT Transformer
For 110V mains, all the windings are put in parallel not series.
I reworked the PSU changing the 2x 50k 50W + 5k 5W HT bleed & 120V DC tap chain
(was broken) for 6x 68K 10W + 27k 5W, & with a series HT warning neon & I used
the freed up space to mount the mains 16uF capacitor.
Wired in this location it is effectively about 10uF when on tune mode & 16uF
when on SSB mode. The transformer is heavily saturated in SSB mode with the
mains TUNE tapping bypassed. The 16uF does the best it can to tune the heavily
saturated HT transformer core (all 3rd harmonic) in SSB mode.
Results were PF of 0.97 in tune mode (up to 600W PEP), & 0.7 in SSB mode (up to
1200W PEP), in the UK there is no need to use the SSB mode with a 400W licence!
Or in other words I saved at least 1 Amp at 240V, so there is more available
for other loads (lights etc) before the genny trip goes.
Why Don't U send an interesting bul?
73 de John, G8MNY @ GB7CIP
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