Re: [CAD_CAM_EDM_DRO] Re: wire gauge and steppers

On Mon, 21 Apr 2003 22:10:00 -0000, you wrote:

>Hi Jan,
>
>my origional post was concerning the wire between the transformer and
>the cap, then between the cap and the terminal strip.
>
>the wires from the terminal strip to the Geckos is limited to the
>Gecko's amp draw, which is very small, and the wire to the steppers
>is the same, very small.
>
>Since the 8 inches between the transformer and the rectifier is 18ga
>and the 2 inches of wire between the cap and terminal stip is 18ga, I
>was wondering if I was getting too close to the ratings.
>
>oddly enough, it seems that on the charts I did find, 18 ga wire can
>handle either 7 amps, or 19 amps, depending on which chart is used.

If the thought of #18 bothers you, and that's ok if it does, then you
can use two pieces of it in parallel.

14 gauge house wiring romex would be ok, but I'd solder things. Solid
wire used to be used for electronics wiring. If you are using crimp
terminals, I'd recommend using the uninsulated type (or sliding the
insulation off the insulated type), soldering them, (then sliding the
insulation back on....)

If there's no flex in the wires, then there's no need for stranded.


Harvey

>
>I have only 18ga stranded wire and telecom wire, or 12 and 14ga solid
>copper (Romex) for house wiring.
>
>I was hoping to not have to run out to Home Depot for a few feet of
>some wire. (hour drive and it is the only place open on sat and sun)
>
>Dave
>
>
>
>
>
>
>--- In CAD_CAM_EDM_DRO@yahoogroups.com, JanRwl@A... wrote:
>> In a message dated 4/21/2003 10:21:07 AM Central Standard Time,
>> madyn@i... writes:
>>
>> > #18 ok to 5 amps... again, guessing..... #18 is used for 10 to 15
>> > amps at 117, so again, no big deal... Household runs are often
>in the
>> > 70 foot range, but at more voltage drop permissible....
>> >
>> > What the heck, #16 or #18 is fine...
>> >
>>
>> Harvey & Dave:
>>
>> I have done such connections for years, both "unipolar"
>and "bipolar". The
>> new "chopper drives" may send an "average" current approaching the
>motor's
>> design-current, but since the DC voltage is much higher (didn't you
>say 35
>> VDC supply?), the actual current from that power-supply's
>transformer and
>> rectifier is considerably less. However, once the filter-capacitor
>> (thousands of µF) is connected across that unregulated DC, the
>current from
>> there to the drives becomes effectively more.
>>
>> ANYway, for currents up to 3 amps, #18 is VERY adequate for the
>kind of short
>> runs you normally have between the supply and the drives or
>switches or
>> connectors. I would have no fear of using #18 for Size 34 and
>smaller motors
>> up to six feet, and probably all the way on up to 12' would be
>OK.
>>
>> The only time I think you would need #16 would be for Size 42
>motors, cables
>> over, say, five feet.
>>
>> Now the old fashioned UNIpolar drives generally sent (usually-
>nearly-) FULL
>> winding-current to the motors, "wasting" the excess available
>voltage over
>> those big power-resistors in series with the +common leads to the
>motors as
>> heat. Modern BIpolar drives such as the Gecko G201 and G210 (and
>other
>> brands I know nothing about) "chop" the DC so those resistors are
>not needed.
>> Those better chopper-drives then DROP the current to about 1/3
>the "max.
>> rated" current when the motors are still for, oh, two seconds.
>Thus, MUCH
>> current is NOT flowing, anyway, so even if the wires were a bit
>small (say,
>> one gage-size smaller than "mathematically correct"), it'd be fine.
>>
>> Here's a tip for EVERYONE who never realized it: If some
>particular AWG size
>> (say #18) is "right" for a given current (say 3 amps), then simply
>ADD three
>> to the gage-number to indicate the size adequate for HALF that
>current (that
>> is, #21 would be right for 1.5 amps); and SUBTRACT three gage-sizes
>for TWICE
>> the current (that is, #15 would be right for 6 amps.) Of course,
>these
>> examples begin with the assumption that #18 is right for 3.0 amps.
>(I think
>> like a transformer designer).
>>
>> Conductors in a cable such as a motor's four our six-wire cable
>might be
>> rated for more current that the same gage-size used as magnet-wire
>in a coil,
>> but this is simply due to the fact that wasted heat is more easily
>dissipated
>> from a loose cable than from a tightly-wound transformer-coil! So,
>in this
>> instance, the thing to keep in mind is the voltage-DROP due to the
>wire's DC
>> resistance at whatever current.
>>
>> What did I miss? HTH! Jan Rowland
>>
>>
>> [Non-text portions of this message have been removed]