[Amps] Alpha 87A Power Supply Question

[Adrian]

Although, I am a VK, , I am also an A class Electrician here, and here 
is how

The SAA wiring rules relates to this matter for best safety, inline;


On 6/5/21 10:01 am, MU 4CX250B wrote:
> Hi Jeff and Jim,
> I happily defer to your greater knowledge of electrical codes, about
> which I know very little. I also understand that amateur equipment
> powered off 240VAC should have four conductor power cords and internal
> circuitry that separates chassis ground from Neutral. In that
> circumstance, AC imbalance currents then return safely through the
> neutral wire, while no load current flows into the ground connection.
> No question that is the ideal setup, to which we should all aspire.

Only L2 and L2 with ground is required. Neutral is not required, in what 
is a ,

simple AC path provided across L1 and L2 with no current imbalance issue 
toi concern us in this application.

The neutral if present should be connected to a terminal in the amp  for 
connection to 120v devices, fan etc,

also fed from L1 or L2. If more than one device share the load using L1 
for some and L2 for the other 120v

devices to share load. If the HV primary fails on one of 2 primaries 
(open circuit), it would be better that the

whole amp shuts down, so I would not recommend neutral connection to the 
center tap if accessible.

If we were dealing with heater banks then yes the neutral would be 
beneficial at the primary load centre tap.


Three or 2 phase supplied heater banks use a neutral to allow maximum 
possible heater banks to operate,

if one bank open circuits> fails ,  in a star (3ph star or wye wired) or 
centre tap (2ph) connection with neutral

connected to the star point or center tap respectively.

nmeutral should never be connected to ground anywhere else in the system 
but at the switchboard 'MEN (main earth neutral)'

connection strip where a neutal and earth terminal block are connected 
to gether and a main eath stake connected to the earth

terminal block.


This keeps ground and neutral potential equal. The appliance (which is 
the amp here), must have its metal body grounded,

unless double insulated from the exterior touched surface. The groung 
connection is purely there for the purpose of keeping

the exterior metal potential minimum and taking the surge currect to 
ground , blowing the supply fuse in the case of insulation breakdown

or other short to earth. It is there to save lives. The chassis should 
never carry AC supply current otherwise.

Connecting a neutral to chassis compromises this safety in known fault 
conditions where the neutral to ground connection removes the safety for the

appliance user exposing that person to potential above ground.


It is a safety issue.


Any old amp should be updated and rewired to match modern standards, 
otherwise you are playing Russian roulette with peoples lives.


vk4tux