[ARC5] 28 volt high-current supplies?

Sat Feb 26 17:12:19 EST 2022

Yes, in my post of 12:47 today, I said:

the inrush seems to be around 300 amps!!

I didn't pull that figure out of the air, but it is an estimate based on 
the measured voltage drop across 2 feet of 8 ga cable (0.63 milliohms 
per foot).
Since my power supply is unable to provide enough current (hoping it 
will when my 220,000 uF cap arrives), it is not reaching run speed. Also 
I need to get a bigger heat sink for my bridge rectifier...

On 2/26/22 15:32, J Mcvey wrote:
> Did you try measuring the start and run current that you are drawing?
>
>
> On Saturday, February 26, 2022, 04:24:14 PM EST, Charles via ARC5 
> <arc5 at mailman.qth.net> wrote:
>
>
> It's not the capacitor on phase A.  Oh pooh. Now I have to look for 
> zebras rather than horses...
>
> Yes, I am aware of the basic motor physics ;) That "about a second" is 
> with a stiff supply. Mine is apparently not stiff enough <that's what 
> she said> :D
>
> My original plan was to acquire a 618T with the 400 Hz three-phase 
> supply - usually much cheaper than the 28 vdc or the 400 Hz single 
> phase versions. But this inverter is becoming a real white elephant. 
> It would be running all the time, not PTT like the ART-13.
>
> Anyway I am tempted to go buy a pair of car batteries and find out, 
> just because I'm stubborn that way! (My two "ARC-5" receivers have 
> their dynamotors, but I only run one at a time, and the 28v supply I 
> built with a handy Stancor RT-204 transformer has no trouble).
>
> Charles, WB3JOK/0 since '76
>
>
> On 2/26/22 15:13, Christopher Bowne wrote:
>> No, just a an Ames (Harbor Freight) 80 buck multimeter with a clamp 
>> on AC or DC ammeter.
>>
>> Peak current is always at initial 0 RPM, as the motor winds up the 
>> counter EMF brings the current down in about a second. Basic
>> DC motor physics.  Considering the instrument pedigree I take no 
>> responsibility for the accuracy of the reported result.
>>
>> As an alternative to floating batteries on the output of a DC supply, 
>> one could implement a step starter circuit, but you would need
>> some hefty dropping resistors and contactor relays.  Wouldn’t lend 
>> itself to quick PTT operation on voice.
>>
>> Chris AJ1G
>> Stonington CT
>>
>> Sent from my iPhone
>>
>>> On Feb 26, 2022, at 15:38, Charles <charlesmorris800 at centurytel.net> 
>>> <mailto:charlesmorris800 at centurytel.net> wrote:
>>>
>>> Thanks, there's a data point of 5 times the nameplate.. What was 
>>> the decay time of that 160 amp peak (did you use a scope)?
>>>
>>> If I HAD a couple of spare car batteries I'd certainly try them ;) 
>>> but have you seen the prices lately? they start at $55 plus core 
>>> plus tax at Wally World...
>>>
>>>
>>> On 2/26/22 13:37, Christopher Bowne wrote:
>>>> I’ve measured the peak inrush current on my ART-13’s DY-17A 
>>>> dynamotor,  it was a nominal 160 amps.  Just float a couple of 12 
>>>> batteries across the output of your supply, make sure that they are 
>>>> fully charged and full sized automotive or deep cycle marine type, 
>>>> small one may not deliver enough peak current to preclude tripping 
>>>> the output breaker in on your high current supply.
>>>>
>>>> Chris AJ1G
>>>> Stonington CT
>>>>
>>>> Sent from my iPhone
>>>>
>>>>> On Feb 26, 2022, at 13:57, Charles via ARC5 <arc5 at mailman.qth.net> 
>>>>> <mailto:arc5 at mailman.qth.net> wrote:
>>>>>
>>>>> I am sure I would have no trouble starting a DY-17 with a 33 amp 
>>>>> full load rating. This beast is 3.5 times that full load draw and 
>>>>> consequently any surge current would likely also be 3.5 times that...
>>>>>
>>>>> Anyway I am going to investigate shorts on the AC side, and my 
>>>>> prime suspect is the (noise reduction?) capacitor on A phase. Hope 
>>>>> it's not the armature. It does have a repair request tag from the 
>>>>> 80's or 90's (don't remember at moment) and an unreadable 
>>>>> "Serviceable" tag. The electromechanical regulator (carbon piles!) 
>>>>> will get a look after I check the cap. Something else I have no 
>>>>> experience with.
>>>>>
>>>>>
>>>>>
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