# Use only two phases of three phase for heating element

I've got a 15,6A kanthal resistor wire (14,84 Ohm) which I use as a 220V heating element, yielding 3410W.

I was wonderig how I could run this element on three phase.

The potential difference between L1 and L2 is say 400V. So could I connect L1 to one end of the wire, and L2 to the other? So I wouldn't use L3 nor would I use the neutral.

If this is possible, It would give me:

400V/14,84Ohm= 26,95A So... 400V * 26,95A = 10780W

Apart from the element not being able to handle the amount energy being emitted.

• Is this a wye or a delta three phase setup? Sep 25, 2016 at 16:19
• a 2 port resistor cannot be shared by 3 ports Sep 25, 2016 at 16:22
• There are only two terminals: the wire leads. I don't have 6 leads to connect to the three phases, hence my question to exploit the potential difference between 2 phases to heat the wire. Would this work?
– HDB
Sep 25, 2016 at 16:51
• If you did want to use all three phases, one option to do so would-be to use a 3-phase bridge rectifier to produce DC, and connect the resistive element to that. Sep 25, 2016 at 20:12

Kanthal A-1 is a ferritic iron-chromium-aluminium alloy (FeCrAl alloy) for use at temperatures up to 1400°C (2550°F). The alloy is characterized by high resistivity and very good oxidation resistance.

Typical applications for Kanthal A-1 are electrical heating elements in high-temperature furnaces for heat treatment, ceramics, glass, steel, and electronics industries.

Source: Kanthal.com.

I was wondering how I could run this element on three phase.

You would connect it between any two phases. The effect of this would be to place an unbalanced load on the supply. If this load is close to the transformer rating it may unbalance the supply enough to cause problems for the transformer itself and other devices on that supply.

Apart from the element not being able to handle the amount energy being emitted.

That depends what you are heating. For example, if the wire were immersed in oil it may be able to handle that current due to good convection whereas in air it might glow like an incandescent lamp for a few seconds before perishing.

[From OP's comments:]I've made a heat treatment oven for steel. It's PID controlled using a K thermocouple and can reach temperatures up to 1000C. The problem is that it takes 2 hours to reach that temperature.

OK. That's either poor insulation or just the thermal mass you have to heat.

I'm already close to 16A 220V single phase, so I can't change the element (already maxed out). I figured that I could use 3 phase power to get a higher power rating. 5000W would suffice, and the elements would handle that without burning through. So I would change the resistor (change lenght) to change resistivity to get 5000W, using L1 and L2 (=400V) instead of L1 and neutral (=220V).

It's not clear how you can't change the element but can change the resistor, but it seems that you have a plan.

One suggestion is that you limit the current through your heater using an SCR / triac dimmer. This will allow you to set any power level up to 100%. This would, in effect, set a maximum power output while the temperature controller controls the temperature.

Figure 1. Phase control using a triac.

Figure 2. A pre-packaged phase-angle controller.

• So what I intend to do should work, right? I would use three phase that I get from the distributor, so the fact that I'm unbalancing (not using all the phases), should not be a problem then? If I were to use a generator, this would be harmfull to the generator?
– HDB
Sep 25, 2016 at 16:56
• "Should not be a problem" in what regard? Is incandescence considered a problem? You haven't given any details of the application so nobody could advise you on that. Sep 25, 2016 at 16:59
• I've made a heat treatment oven for steel. It's PID controlled using a K thermocouple and can reach temperatures up to 1000C. The problem is that it takes 2 hours to reach that temperature. I'm already close to 16A 220V single phase, so I can't change the element (already maxed out). I figured that I could use 3 phase power to get a higher power rating. 5000W would suffice, and the elements would handle that without burning through. So I would change the resistor (change lenght) to change resistivity to get 5000W, using L1 and L2 (=400V) instead of L1 and neutral (=220V).
– HDB
Sep 25, 2016 at 17:25
• See the update. Sep 25, 2016 at 17:42

L1, L2 or L3 to neutral will give you 231 volts. If you connect the element between line and neutral, it will dissipate 3594 watts. Unless you have a method for increasing the heat dissipation capacity as suggested by @Transistor, you should connect the element between L1, L2 or L3 and neutral. Depending on the other loads on your 30phase source and the source capacity, the additional load and the imbalance introduced may or may not be a problem.

• Look at it ceteris paribus. Whether the wire would or would not survive is not important. I want to know if using L1 and L2 instead of L1 and neutral is a possibility. Other loads and load capacity are in range. The imbalance introduced might mess up a generator...
– HDB
Sep 25, 2016 at 17:31
• So the imbalance is the only issue and it seems that must not be a concern either.
– user80875
Sep 25, 2016 at 17:54