Calculating Current Draw in Electromagnetic Coil

[frankenstein]

My situation is this. I have 6,560 ft (4 lb) of polyurethane-nylon coated #27 gauge round wire wound in a coil with an air core of 1 1/8 in. wide x 4 in. long x 4 in deep. I don't want to destroy my precious electromagnet so I'm afraid to give it some current. What would happen if I attached a 12 volt car battery? The wire at 6560 ft has a resistance of 337.6 $$\Omega$$. Using ohms law that voltage across any pure resistance is equal to the strength of the current in the resistance times the strength of the resistance... we get the equation: V=IR. Rearranging it: I=V/R

With a 12 volt battery and that given resistance I should be drawing .0355 Amps?
But I want 1200vdc - 6,000vdc or higher.
With 1200vdc following the equation I should be drawing 3.55 Amps?

Won't I burn the insulation through and short? How can I achieve a very high DC voltage while maintaining an amperage under the wire's conservative amp rating of .268 Amps (based on 750 circulare mils per Amp) or the wire's Max Amp rating of .403 Amps (based on 500 circular mils per Amp)?

My basic question: How can I operate this specific electromagnet with a 360vdc - 6,000vdc power supply at an amperage that will not hinder the performance of the electromagnet?

It may be helpful to know that I am switching this electromagnet off and on many times per second, reversing polarities every time it's turned on. I'm using a high voltage magnetic reed switch to pulse the negative attaching a full wave bridge rectifier BEFORE the switch to rid myself of all the sparking and to charge another battery. :) see any problems with my circuit other than it being a normal HV electric chair? lol

 

[Redbelly98]

A better approach is to first figure out what strength magnet you need.

My basic question: How can I operate this specific electromagnet with a 360vdc - 6,000vdc power supply at an amperage that will not hinder the performance of the electromagnet?

If we go with the 0.268 A figure, you can apply at most

V = I R = 0.268 x 338 V = 90V

(And, it would be good to measure the resistance with an ohmeter, rather than relying on a calculation.)

Also, your wire insulation is probably rated for at most a few hundred volts, possibly less. Don't even think about applying kilovolts unless you know the voltage rating of the wire+insulation you have.

edit:
p.s. Welcome to PF!

 

[astrokreng]

I appreciate your thorough approach to calculating the current draw in your electromagnetic coil and your concern for the safety of your equipment. It is important to understand the potential risks and limitations of using high voltage and high amperage in any electrical circuit.

Based on Ohm's Law, it appears that your coil can handle a maximum current of 0.403 Amps without exceeding the maximum amp rating of the wire. However, as you mentioned, using a 12-volt car battery would only result in a current of 0.0355 Amps, which is well below the maximum rating.

To achieve a higher DC voltage without exceeding the amp rating of your wire, you may want to consider using a voltage multiplier circuit, such as a Cockcroft-Walton multiplier. This will allow you to increase the voltage without increasing the current, as the voltage is divided across multiple stages.

Another option is to use a high voltage power supply specifically designed for your application. These types of power supplies are designed to provide high voltage at low current, which is ideal for applications like yours.

Additionally, it is important to consider the insulation of your wire when operating at high voltages. You may want to use a wire with a higher voltage rating or add additional layers of insulation to prevent any potential short circuits.

In terms of your circuit design, it is always recommended to consult with a qualified electrician or engineer to ensure the safety and effectiveness of your setup. It is also important to follow all safety protocols and use proper protective equipment when working with high voltage and high current.

Overall, it is crucial to understand the limitations and potential risks associated with operating high voltage and high current circuits. With proper precautions and careful consideration, you can achieve the desired voltage without compromising the performance or safety of your electromagnet.