I wanna buy an electromagnet from aliexpress and many of them are lifter magnets and have 6V, 12V, 24V and 5kg. So if i choose the 6V option does that mean the magnet can lift 5kg at 6V? Why would anyone buy the other options then (same price)?
4
-
\$\begingroup\$ Did u get Watt rating for V rating yet? \$\endgroup\$– D.A.S.Commented Jan 8, 2019 at 2:49
-
\$\begingroup\$ Not yet, but from the comments some people say its weak some say its ok, but i guess thats what you can expect from cheap Chinese stuff. Other than that im not really sure if im gonna buy anything as im having doubts about the project i intend to use them on, and i dont know if i wanna wait 30 days to recieve it (paying for shipping is out of the question). \$\endgroup\$– Luka KosticCommented Jan 8, 2019 at 4:36
-
\$\begingroup\$ Id upvote but have less than 15 rep so cant, as for marking as answer Spehro answered first and it was sufficient. Tho yours is more useful. \$\endgroup\$– Luka KosticCommented Jan 8, 2019 at 4:45
-
\$\begingroup\$ The cost should be about 0.25$/kg force. Go for a bigger diameter, check local online \$\endgroup\$– D.A.S.Commented Jan 8, 2019 at 4:53
Add a comment
|
2 Answers
\$\begingroup\$
\$\endgroup\$
3
The total power requirement (watts) will be similar for the different voltages. If you pick a 6V one it will draw about 4x as much current as a 24V one.
The higher the rated voltage, the more turns of wire are used, and the wire will be thinner (higher AWG number). Since the magnetic force is proportional to ampere-turns the number of turns needs to be 4x larger at 24V compared to 6V.
answered Jan 7, 2019 at 5:02
-
\$\begingroup\$ So more turns but thinner wire, thats why the price is the same? \$\endgroup\$ Commented Jan 7, 2019 at 5:06
-
\$\begingroup\$ Yes, the volume of wire (grams of copper) is about the same, and the rest of the assembly is identical. In practice it's probably a bit more expensive for the manufacturer to make the coils with more turns, but not that much. You would want to pick the one that's most compatible with your power supply, or perhaps so you can use thinner wires to power the device. \$\endgroup\$ Commented Jan 7, 2019 at 5:08
-
\$\begingroup\$ the net result is in a good design Voltage won’t matter over a small range of powers \$\endgroup\$– D.A.S.Commented Jan 7, 2019 at 20:37
\$\begingroup\$
\$\endgroup\$
If all the air gap between windings could be filled, and could dissipate the same heat per unit volume, it probably wouldn't make much different on the Voltage for the same size.
Reducing the wire gauge 3 times reduces the the resistance by 2 and doubles the cross-sectional area and the power dissipation per Amp-turn reduces by 4.
So the winding thickness per Amp-turns tends towards a constant product.
But heat dissipation and thermal conduction of the windings may be a bigger factor so diameter , thickness voltage , may be a bigger factor.
Get specs on the kg per Watts and compare with US made units from 5 to 15 kG/Watt in this voltage range and size. but more expensive.
Then pick the highest kg/W of continuous use holding force.
If they don't give Watt specs... beware e.g. https://www.ebay.ca/itm/DC-24V-5kg-11LB-Electric-Lifting-Magnet-Electromagnet-Solenoid-with-Coil-/302791456929
ALso beware of the differences than make the magnetic steel core become self-magnetized. This will tradeoff cheaper materials for higher kg/W and self magnetization that requires degaussing at some point.
These are cheap but do 25 kg yet only 3.125 kg/W = 8 Watts https://www.ebay.ca/itm/55LB-25kg-Electric-Lifting-Magnet-Electromagnet-Solenoid-Lift-Holding-40mm/141890308664?epid=1284334493&hash=item2109524a38:g:5tAAAOSwWxNYnVrp
