Are induction stoves considered inductive loads?

Question

I know a washing machine and a coffee grinder are considered inductive loads so when doing math for wiring you would multiply wattage by 2x to be on the safe side. Just one plate of my inductive stove, apparently, is the biggest load in the house. It says 2100W on it. I wonder if I should treat it as a 4000W load when doing wiring. I have a strong grid connection so it was not an issue so far, but I am planning to add some batteries and the difference between 2KW and 4KW would be a major issue.

So the specific issues I'm concerned about:

1. Power factor. Do typical induction stoves have a power factor close to a washing machine?
2. Inrush / collapsing flux when you turn it on/off. I wonder if that might be even worse than in a washing machine. Once I had a plug come loose on that stove and before it switched itself off, it arc welded a few square millimeters off the plug and blackened the wall outlet.

Are there any rules of thumb about how to treat induction stoves when doing wiring?

Answer 1

An induction stove isn't just an inductor connected across mains. A typical stove rectifies the mains power into DC, and drives the coils at a high frequency (tens or hundreds of kHz) through a resonant circuit. Ideally, the 'inductance' just provides a means for power transfer, and the load appears resistive. It is much like a voltage transformer. The main question is how the input rectifier & filter behaves.

https://www.electronicsforu.com/wp-contents/uploads/2017/04/Screen-Shot-2017-04-14-at-3.22.46-PM.png

In the image above, the heating coil (cooktop) is represented by the inductor shown connected to the two IGBTs. The cookware itself (not explicitly shown here) is magnetically coupled to the heating coil. The 'resonant tank' refers to the combination of two capacitors, heating coil, and cookware. The MCU detects the resonant frequency of this group of components and drives the IGBTs near that frequency.

To answer your questions:

1. A typical inductive stove would use active power factor correction within the rectifier to maintain a PF close to 1, which should be better than a typical washing machine.
2. The coils are isolated from mains by the resonant power supply. You won't see the same inrush / inductive kick when turning the stove on /off as you would with a motor / inductor. These coils have a lower inductance and operate at a much higher frequency than a washing machine motor. Regarding your example, any loose electrical connection could cause arcing, regardless of the nature of the load.

I can't give professional wiring advice, but from an electronic perspective, an inductive oven should behave similarly to a other electronic loads, like your computer or TV. Which usually don't need special consideration.

Answer 2

Found this from the 2014 report "Induction Cooking Technology Design and Assessment"

https://www.aceee.org/files/proceedings/2014/data/papers/9-702.pdf

It was presented at the 2014 ACEEE Summer Study on Energy Efficiency in Buildings.

Apart from energy consumption, the impact of any consumer electronics device on the power quality of the grid should be considered. Evaluation by EPRI (CEC 2014) found the current harmonics of induction cooking technology to be relatively low, below 6% THD (of current) for all load levels. In addition, power factor was measured at 0.98 and above. This performance is unlike that of switching power supplies, which draw current in large spikes. Although induction cooking makes use of high-frequency switching power electronics, these devices do not naturally exhibit poor power factor like switch-mode power supplies because their voltage is unregulated. Rather, power flow is controlled by varying the switching frequency of the resonant converter driving the magnetic coil.