I am working on a simple project which involves in supplying a power to couple of loads using battery and Inverter. The capacity of my inverter is 2000W/ 4000W(10sec). I have connected couple of loads to this in which secondary load starts and runs at 1A 110VAC max and the primary load start varies between 2A and 30A 110VAC depending on the setting for less than 1sec and runs at 2A. Now my problem is when turning ON the primary load at high setting, (when start power is more than 23A) the secondary load restarts. I am thinking about using a capacitor inline to my primary load for starting it without disturbing the secondary load. I need some advice in what capacitor can I use for this condition.


simulate this circuit – Schematic created using CircuitLab

  • \$\begingroup\$ Why you think a capacitor might solve your problem? \$\endgroup\$ – soosai steven Jun 29 '16 at 14:57
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    \$\begingroup\$ The capacitor will not solve your problem. Your LOAD2 needs to be able to deal with the supply transient caused by LOAD1 or you need a better inverter to not have a substantial transient. \$\endgroup\$ – user2943160 Jun 29 '16 at 15:02
  • \$\begingroup\$ A quick fix for this would be to use two separate inverters, thereby decoupling (mostly) the loads from each other. \$\endgroup\$ – uint128_t Jun 29 '16 at 15:03
  • \$\begingroup\$ How big a deal is it that the second load restarts? \$\endgroup\$ – Andy aka Jun 29 '16 at 17:21
  • \$\begingroup\$ Thank you. So I think I am totally wrong. The capacitor is not the solution for the problem. Is there any other way I could come around. \$\endgroup\$ – Edwin Divakaran Jun 29 '16 at 18:13

What you are suggesting makes no sense. Capacitors don't work how you apparently think they do. Capacitors can temporarily hold up a DC power supply, but not AC as you have.

Especially considering your apparent level of electronic understanding, the answer is to go buy a bigger inverter. No, seriously. Fundamentally you have a 20 pounds of stuff in a 10 pound bag problem. Get a bigger bag, or stop trying to cram so much stuff into it.

Your numbers also don't add up. Your inverter is supposed to be able to handle 4 kW for 10 seconds at 110 V. That means 36 A. You're not exceeding that. Possibly the input to the inverter can't keep up with the load. Is this battery really able to supply 4 kW for 10 seconds. If this is 12 V, for example, then that would be 333 A. Even if the battery can do that, maybe the cable between the battery and the inverter is dropping too much voltage.

Again, the basic problem is that your system is under-specified. Either the battery, inverter, or the connections between can't handle the full power, or can't really deliver as promised by the sales BS.


Check your loads:

  • \$ P_1 = VI_1 = 110 \times 30 = 3330~VA \$.
  • \$ P_2 = VI_2 = 110 \times 2 = 60~VA \$.
  • \$ Total = 3390~VA \$. This is 85% of the 10 s rating of the inverter.

If your current requirement statements are correct the inverter should handle it. You need to check with the specifications or the manufacturer what the output will look like at 4,000 W. You may find that the voltage droops significantly or that the waveform distorts enough to upset Load 2. More than likely you will find that the 4,000 W specification is more wishful than actual.

A capacitor will not solve this. You may be confused with use of capacitors as short-term storage in DC circuits (where they do work). Due to the alternating nature of AC it is not possible to store alternating energy in a capacitor. In any case, a passive component can not give "a power boost".


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