Garage sale. Allen-Bradley 3 phase motor controller (starter). New, never
used. $ 5.00 !!!!!!
Not as good as Iggy, buy I still feel fortunate.
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.
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.
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. 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. If that is not what I purchased .... oh well, it was only $ 5.
On Sat, 31 Jul 2010 11:47:07 -0700, "Ivan Vegvary"
"heaters" are mica posts wound with resistance wire. They are in series
with the wire feeding each phase input...IE there are 3 of them and the
motor wiring goes through them from the power supply.
When any one of them draws too much power..they heat up and cause a
bimetal switch to open up, stopping power to the motor.
Its a "fuse", but one that is resettable. Think of it as a circuit
breaker..which indeed it is. Some "heaters" are replaceable with
smaller or larger values so if you need to have it trip at less amps,
you use a smaller set, or at more amps..a larger set.
Very simple, nearly universal in use in virtually all "heavy" machinery.
Since the average "fuse" for machinery costs from $5-30 EACH..having
something reliable and resetable is very important. Particularly when
you have 3 fuses in each machine.....
Actually -- sometimes they play it cheap and only put them on
two of the three wires. The third is straight through.
They won't trip anyway if you are just a little over current.
If you are far enough over current to be a problem, at least one of the
two will be seeing enough current from that third wire so it will trip
Of course, the contactor will open all three power wires even if
there are only two heaters.
Sometimes they are instead a ratchet wheel with hardened wax as
lubricant, and when it gets hot enough to melt the wax, the wheel turns
and releases a spring lever to open the circuit. The bimetal switch has
the advantage of being self-resetting, while the "wax lube and ratchet"
style requires you to open the housing and note which one tripped and
needs to be reset. This information might be useful if there are
frequent nuisance trips. :-)
There may be yet more techniques for the heaters to do their
job. The ratchet and wax design was used in certain phone line
circuitry to disconnect the user's line if it started getting too much
current pumped through it (e.g. little Johnny plugged the phone wire
into the 120 VAC outlet. :-)
The OmniTurn CNC lathe used a similar heater, but it used a very low
temperature alloy that melted and allowed the ratchet to spin, opening
the 2 servo feed lines that ran each servo motor. I noted that the last
couple lathes I installed, used a more (cheap) traditional breaker
switch as might be found in an electronic assembly.
The contactor I have on my Harrison L5 has three 'heaters' one on each
phase, these each heat their own bi-metal strip that moves a bar, the
bar is attached to a cam which then moves a (spring loaded) lever off
from a contact, the power to the electromagnet is through that contact
so when the bar moves enough, power to the electromagnet is cut and
the machine shuts down. As soon as the bi-metal cools it 'resets' and
the machine can be turned on again.
It can be adjusted from IIRC 10A down to 0.3A by moving a lever
attached to the cam.
Very simple and hardly anything to go wrong.
and they have been in use for at least 60-70 years too, I'm pretty
sure mine was original equipment on a lathe which was made in the
Even though I've converted to a new motor with a VFD I've kept the
contactor (although I replaced the (few) pieces of wiring in mine as a
piece of mind measure), works perfectly fine with just single rather
than 3 phase too!
O.K. The "control voltage" does not apply here. This is a
purely mechanical switch. The starters for which a "control voltage"
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)
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
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. :-)
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.
Nope -- as far as I can see, there is no magnetic feature in
this, just purely mechanical.
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.
The item shown in the image at the link provided below, is a mechanical
starter with the combined feature of over-current protection for the motor.
The 3 pockets/wells below the red stop button (with 3 additional pairs of
screws, above and below the wells) are where the heaters are installed.
Most enclosed starters which are furnished inside a suitable box, have
labels with a chart for selecting the correct heater currents, based upon
the line voltage and desired/chosen load.
Over-current/overload heaters/protectors react faster than a motor's
internal thermal protection (if a particular motor even has a thermal
protection device, 3-phase motors typically don't).
The heater protection feature in the starter will save a motor if the
equipment experiences a jam, bearing failure or other excessive mechanical
load which causes a rise in the motor's current draw.
The correct heater current rating will be greater than the run/idling
current of the proposed grinder application, since the motor's current draw
will rise when actual grinding is taking place.
Heaters are selected to cause the starter to hold at normal load current
demands, and to open quickly at higher load demands (faults).
Some starter heater devices are mechanical (such as those I see shown below
the starter image) and others just look like a numbered, bare strip of
formed metal, which cause temperature-sensitive components within the
starter to react.
Many single-phase machine motors only have internal temperature protection
(cheaper motors usually don't), which in many cases, won't protect the motor
in the event of a sudden jam or other fault that causes an excessive current
With properly-selected heaters in an over-current protection starter, the
machine will be stopped before motor damage occurs.
"Ivan Vegvary" < firstname.lastname@example.org> wrote in message
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