I beg you pardon if the question sounds trivial. I have a Power Supply that can provide a outer voltage between 0 and 32 V , and an outer current between 0 and 10 A. I would like to connect a resistance heating wire to this power supply, so that it should archive the maximal(needed) heating power.

1)If one uses a wire with the total resistance of 20 Ohm at a constant current of 3 A for 2h that one should archive 129600 J (Q=tRI^2), Is it correct?

2)The user manual of the power supply states that: "output voltage and output current can be set from 0 up to maximal value, both operation modes, constant Voltage(CV) and constant Current (CC) are selected automatically ()auto cross over."
If I am using the Constant Voltage Mode, at a voltage of 30 V and a resistance of 1 Ohm that the required current should than be 30 A, what the supply can not provide, and so it is not possible to built. Is it correct?

3) For maximal heating power I should choose maximal resistance and current , withing the technical possibilities of the Power Supplier?

4)Is there a equation that helps to estimate how hot will the conductor be after some time?

Thank you very much and have a nice day :)

  • \$\begingroup\$ Perhaps your supply will output Vmax and Imax simultaneously, in which case 3.2 ohm load resistance will absorb max power. You'd have to turn up both Volt-control and Current-control to maximum. \$\endgroup\$ – glen_geek Jun 21 '17 at 15:08

Yep, pretty much an eclectic mix here.

  1. If a wire has 20 Ohms and handles/needs 3 A, you need a PSU with 60 V output. Your benchtop PSU can't deliver this, so the rest of calculations is a moot point;

  2. If you use a 1 Ohm wire and set your benchtop PSU to DC 30V and 10 A current limit, the PSU will reach the 10 A limit at 10 V, and will enter "constant current mode", delivering 10 V and 10 A;

  3. Your PSU has maximum 32 V and 10 A. Therefore, the maximum power output of 320 W will be at 32 V and 10 A. To get into this mode, your wire resistance must be 32/10 = 3.2 Ohms;

  4. There are equations, but the answer will strongly depend on wire geometry and its orientation relative to the field of gravity, ambient temperature, airflow velocity (if forced), etc. Google for some calculations for "hot wire cutters".


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