Induction cooker

[Pony]

Hi Guys

Anyone have a induction cooker?

If so how much power does it draw? Does it work well?

P

[superdiy]

Yes, we have a "single plate" one.  Used it about 4 times and now it sits in the cupboard.  If I remember correctly mine draws up to 2000W.  It does heat the food etc faster than a conventional plate, but peak current draw is still a lot.  So, if you intend to save on total usage, then you can go for it, but if you want to lower your peak draw e.g. from an inverter, the induction cooker won't help much - it may even draw more (peak) power than a conventional plate turned on low heat.

 

Keep in mind that not all pots and pans work on the induction cooker - easy test is if a magnet will stick to the bottom of the pot or pan, it should work on the induction cooker.

[Tropman]

After careful scientific evaluation I bought an Induction cooker. It happened like this. Being a sucker for a bargain I opened the bidding for a griddle pan on Bid or Buy, and duly won the auction. When the pan arrived I was surprised to see that it had a shiny round metallic insert on the bottom of the pan. "What's that for I said to my partner"? Being knowledgeable from a minor addiction to 'new home TV programmes' she said "it's for an induction cooker" To rectify my ignorance of these culinary matters I Googled and U tubed them; then, being a sucker for a bargain I found one with almost R500 off the list price, so I bought it.

It is a Russell Hobbs single plate cooker drawing a maximum of 2100 watts, however it is adjustable down to 100 watts and usually operates at about 500 watts, after I have used an initial setting of 800 watts to heat the pan. It is clean and efficient and has enabled us to bring out of disused storage an old fashion cast iron frying pan and a cast iron cooking pot, both of which function perfectly as long as you can lift them!

It is a useful adjunct to my solar set up as I have left out the oven and hot plates from my system. I would recommend an induction cooker to fellow 'power  forumers, perhaps you can benefit from my careful scientific evaluation!!

[Arandoza]

Tropman, can u post a picture and detailed model of the unit you use?

Sounds promising, my take on induction was better efficiency but still the high load. Your unit sounds ideal.

[Tropman]

It' a Russell Hobbs RHIC202. I bought mine from Takealot, but Loot have them R50 cheaper. They respond much quicker than a glass top stove and seem to cook with less burn on the base of the pan.

In the attached picture of the old cast iron pot we cooked kudu mince today. The pot was pre heated at 1000 watts for a few minutues, while the meat was browned: then it was turned down to 800 watts, then 500 watts and ultimately left to simmer quietly at 300 watts. There was 1Kg of meat together with onions, leeks, celery, carrots and peppers, so the pot was about one third full.

To the tight of the pot is a visual display of the power usage.

[superdiy]

22 hours ago, Tropman said:

After careful scientific evaluation I bought an Induction cooker. It happened like this. Being a sucker for a bargain I opened the bidding for a griddle pan on Bid or Buy, and duly won the auction. When the pan arrived I was surprised to see that it had a shiny round metallic insert on the bottom of the pan. "What's that for I said to my partner"? Being knowledgeable from a minor addiction to 'new home TV programmes' she said "it's for an induction cooker" To rectify my ignorance of these culinary matters I Googled and U tubed them; then, being a sucker for a bargain I found one with almost R500 off the list price, so I bought it.

It is a Russell Hobbs single plate cooker drawing a maximum of 2100 watts, however it is adjustable down to 100 watts and usually operates at about 500 watts, after I have used an initial setting of 800 watts to heat the pan. It is clean and efficient and has enabled us to bring out of disused storage an old fashion cast iron frying pan and a cast iron cooking pot, both of which function perfectly as long as you can lift them!

It is a useful adjunct to my solar set up as I have left out the oven and hot plates from my system. I would recommend an induction cooker to fellow 'power  forumers, perhaps you can benefit from my careful scientific evaluation!!

Hi Tropman, have you actually measured the wattage at the different settings or is that what they indicate on a dial / display?

[Tropman]

I have reported the display readings, which react in a quantitative way in that the response from the cooking pot or pan goes from vigorous action to 'off the boil' as you decrease the settings. However I will put a wattmeter on them tomorrow if I get time and post the results

[superdiy]

3 hours ago, Tropman said:

I have reported the display readings, which react in a quantitative way in that the response from the cooking pot or pan goes from vigorous action to 'off the boil' as you decrease the settings. However I will put a wattmeter on them tomorrow if I get time and post the results

I am not saying that it is the case, but what they usually do is to only change the duty cycle on "lower" power settings. In other words (ignoring efficiency and power used by controlling circuit, display etc.) if you set it to 2100W, it will draw 2100W all the time. If you set it to 1400W, it will draw 2100W for 67% of the time and draw 0W for 33% of the time. If you set it to 800W, it will draw 2100W for 38% of the time and 0W for 62% of the time. The switching rate (from full on to full off) might be at 2 times per second or 100 times per second, I don't know, but the point I want to bring across is that the power is not necessarily varied, but in most cases the duty cycle is varied. So the problem with induction cookers is where someone want to power it from an inverter, the inverter will have to be able to handle the full 2100W and not only the 800W or 500W you've set it to.

A microwave oven works on the same principle, if you set a 1000W oven to a power setting of 700W, it outputs 1000W for 70% of the time and 0W for the other 30% of the time. In microwave ovens the duty cycle is just much lower - few seconds on, few seconds off, few seconds on, few seconds off.

[Tropman]

You are obviously much more knowledgeable than me on these matters, but for what its worth I set up the cooker with a watt meter and found that for readings on the cooker of 800 watts and above the meter agreed approximately with the settings. For settings of 500, 300 and 100 watts the readings did not agree at all. No doubt you are correct in your description of how the induction cooker works. Does the fluctuating power draw have any adverse effect on the inverter and/or batteries? I have a 5KVA Axpert (Mecer) set up to operate on lights and household plug circuits only. I control my use of appliances so that I almost never exceed the four kilowatts that the inverter is designed to manage.

[___]

It's also possible that it uses a mechanism not unlike a dimmer switch. It's the same principle of duty cycle, except it actually chops away part of the AC waveform. Creates horrible radio noise if not properly shielded and all that. This type of control measures low on watt meters, but inverters still don't like them. The average power might be low, but it still has a rather horrible power factor which means the VA figure is much higher than the Watt figure, and the inverter cares about the former...

It is of course possible that it actually converts the power to DC and has a high-frequency sort of drive to things... I have no idea how these things work. If you have an oscilloscope and a current transformer, that would be the way to check. Does the current waveform make a smooth sine wave while it's running at part power :-)

[___]

For example, I made this current vs voltage waveform on my scope some months ago. It's a uniontech LED downlight, and I was using a shunt resistor to measure the current (which creates that little bent in the waveform), but it does give you an idea. The voltage waveform is nice and smooth, but the current waveform is toothed and has a higher peak than it would if it was smooth. So while the lamp is 5W, it's over 10VA. This is due to the way the SMPS works, not a dimmer, but same principle really.

[Pieter Lourens]

On 2016/08/04 at 4:07 PM, superdiy said:

I am not saying that it is the case, but what they usually do is to only change the duty cycle on "lower" power settings. In other words (ignoring efficiency and power used by controlling circuit, display etc.)

Hi @superdiy,

That makes so much sense, and I struggled to find the same explanation before. I find that my solid plate stove does a similar thing in that once the plate reaches temperature that a relay will switch on/off to maintain temperature. It probably does not function exactly the same but it got me thinking. Please challenge my thinking.

I understand that:

1) a gas hob offers constant energy available instantaneously

2) a induction plate is similar to a gas hob but seems like lower energy settings may have a duty cycle

3) a solid plate hob has a duty cycle, mine does

As such should I fry an egg the gas and induction hob will use the least energy. However, at full capacity (e.g. 2kW) over a 30 minute cooking session, the solid plate may use less energy because of the duty cycle?

I assume this is not true because of other technological reasons? I am in doubt if it is really a worthwhile to move to other appliances than a solid plate stove.

All opinions welcome

[Douw G. Gerber]

I use an induction plate to boil my kettle.  I have it set to 1300w.  I can see in real-time when used my inverter load goes up by +-1300w.  But I do agree when set to the frying setting I can see the duty cycle kicking in based on different values - but I am pretty sure on the water boil setting it only uses what I have set it to.