On 2010-07-31, Ivan Vegvary wrote:
"Ignoramus18915" wrote in message
...
On 2010-07-30, Ivan Vegvary wrote:
[ ... ]
I asked this group some 2 years ago on whether I can substitute a single
phase starter for a 3 phase (3 horse power) pedestal grinder. My
thinking
was that in case of power outage at least two of the three power leads
would
be disconnected, leaving me safe. You all said that I am NUTS!!
Well I've waited and finally scored.
what is the control voltage?
Iggy, as always, thanks for your interest.
Model no. of the control is 609-AAW3. At 208-240 volts, 3 phase, it is
rated for 3 horsepower.
Here is a link to the model.
http://www.plchardware.com/Products/RA-609-AAW.aspx
O.K. The "control voltage" does not apply here. This is a
purely mechanical switch. The starters for which a "control voltage"
apply a
1) A three-phase contactor (think relay on steroids). The coil
voltage is the "control voltage" in question. It can be AC or
DC, and totally different from the *controlled* (switched)
voltage.
2) Heat coils through which the current to the load flows.
3) Adjacent to the heat coils are switches which are held
closed by linkages which will release when they get hot enough.
The heat coils are matched to the nominal current of the load so
the switches won't get hot enough to open under normal
conditions, but if the motor stalls, or a winding opens, or any
of a number of other problems occur, the contacts open.
If you rewire the motor from one voltage to another, the heat
coils need to be replaced to match the changed current the motor
will draw. (E.g. it will draw about half the current if you
rewire from 240 VAC to 480 VAC, or will about double if you
rewire from 480 VAc to 240 VAC.)
4) An extra set of contacts on the contactor (hold contacts) in
(1) above which will apply power to the coil as long as the
relay is closed. This coil power also flows through the
switches by the heat coils. So -- if any one of the heat
switches opens, the coil drops out, and power is removed from
the motor.
5) Two pushbuttons -- one normally closed (Start button) which
is wired in series with all the heat coil switches and the
contactor "hold" contacts which can be used to stop the motor by
dropping out the relay.
And one normally open pushbutton (Stop button) which is wired in
parallel with the "hold" contacts on the contactor. Pushing
this will apply power to the coil and pull in the contactor
contacts to apply power to the motor -- as long as none of the
heat coil switches is open. (And, as long as you aren't holding
the stop button with the other hand. :-)
Of course mine comes in a metal mounting box with appropriate lock-outs.
Iggy, there's all sorts of literature about 'heaters'. I have no idea about
what they speak.
Described above. They do not apply to what you got.
I don't see any clues that it may also be a circuit breaker, so
I think that is just a plain high-current three phase switch.
I assume that I am getting an on-off switch that is
magnetic (holds on as long as power is applied) and trips in case of power
failure.
Nope -- as far as I can see, there is no magnetic feature in
this, just purely mechanical.
If that is not what I purchased .... oh well, it was only $ 5.
And it at least switches power off to all three wires at once,
so you don't have the winding hot when you start to work on it. (Of
course, you should unplug it anyway. :-)
I don't think that you need the magnetic feature for a grinder
assuming that if the power goes out, you at least remember to push the
"Off" button before going out to see whether you can reset the breaker
and restore power, or whether you are at the mercy of the power company.
(Hitting that "Off" button does require seeing it -- which is one of the
reasons that I always keep a 3-LED flashlight (size of a Mini-MagLite)
on my belt.
Enjoy,
DoN.
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