1500 watt inverter - will I damage it?

kwastizzlekwastizzle Registered Users Posts: 2
I have a 1500 watt inverter and I’m looking at getting a glass plate induction cooker. The cooker draws from 100-2100 watts, I’m wondering if I don’t use the cooker over roughly 2/3 the temperature setting will that be a problem for the inverter? 
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  • BB.BB. Super Moderators, Administrators Posts: 31,451 admin
    Welcome to the forum Kwastizzle,

    I do not know. I have never used an Oscilloscope to measure the current profile of an induction cooker.

    A good quality modern induction hot plate should have an AC input stage that prevents high current spikes--And if you can ensure that your hot plate always operates at 2/3 power (not temperature) or less, then it should be OK with your inverter.

    Your inverter should be capable of near 2x rated output for a few seconds (surge current to start a motor, etc.). And even operation at full power should not "kill" the inverter--If anything, the inverter may indicate over current output and/or just shut down until load is removed/DC input power is reset.

    Notice I said "power" and not temperature. Some induction cookers may have a "temperature" function--I.e., you set for simmer at boiling temperature. The cooker could use full power when a cold pot is placed on the induction coil, and dail back the power when the pot is "hot". So you may have that variable to deal with too.

    Make sure you have very heavy/short DC power cables from your battery bank (positive cable with fuse/circuit breaker) to your DC input of your Inverter... You need to keep the voltage drop reasonably low and use heavy cable to avoid overheating. For example, a 1,500 Watt inverter running on a 12 volt battery bank will take:
    • 1,500 Watts * 1/0.85 AC inverter eff * 1/10.5 battery cutoff voltage = 168 Amps
    So, you would want fusing/breaker/wiring for the DC circuit to be rated around:
    • 168 Amps DC current * 1.25 NEC derating = ~210 Amps or higher (200 Amp rating would be OK too)
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 31,451 admin
    I should add--An AC inverter when subjected to an overload on the AC output should shutdown safely and reliably. And most do...

    However, on occasion, the inverter can get damaged. Hopefully it will not happen to you. Just too many brands/models/etc. of inverters out there to make a blanket statement about quality/function.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kwastizzlekwastizzle Registered Users Posts: 2
    Thank you for clearing a lot of that up with the detailed response. I have all those things in place so I will give it a go.

    Cheers

    - kwastizzle
  • BB.BB. Super Moderators, Administrators Posts: 31,451 admin
    You are very welcome Kawstizzel,

    If you want to go down a dark hole--You can get some instruments to measure/monitor your energy usage... Both on the AC side and the DC side.

    Some AC capable meters:

    https://www.amazon.com.au/s?k=ac+power+meter&ref=nb_sb_noss_1

    And some DC meters:

    https://www.amazon.com.au/s?k=dc+power+meter&ref=nb_sb_noss

    And/or you can get an AC+DC Current Clamp Digital Multimeter--Much safer and easier method to measure current:

    https://www.amazon.com.au/Auto-Ranging-Technology-Klein-Tools-CL800/dp/B019CY4FB4 (mid-priced unit)
    https://www.amazon.com.au/s?k=uni-t+ut210e&crid=2LFRYG17D3NEL (less expensive but "good enough" meter such as the UT210E)

    Note: I am guessing as to what is available in Australia... And the mess with COVID and issues with China, so price and availability is all over the map.

    And there are AC only current clamp meters--They are perfectly good meters, but if you want to measure DC current, you need to get one that is DC+AC capable current clamp (the meter leads for both will measure AC+DC voltage, resistance, etc.--So that you have to read the product descriptions closely--I.e., AC only clamp current, but AC+DC voltage capability).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,247 ✭✭✭✭✭
    I think most Induction systems, use "batched full power".   They run full power until the temp is reached, then cycle Off - On as needed (Just like a PWM charge controller, either fully ON or fully OFF )
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  • mcgivormcgivor Solar Expert Posts: 3,729 ✭✭✭✭✭✭
    Mike may be correct, full power thru pulse width modulation to maintain setpoint temperature, the prudent thing to do would be to find out using a grid source and a power monitoring device. The power factor along with harmonics generated from the switching power supply may not play well with an inverter matched to the power demand, particularly high frequency lower cost types, modified sine wave should be avoided entirely.
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