Powering an AC load through an Inverter

[zdas04]

I am about to install a vessel with electric actuators. My client specified AC power and so I got AC actuators. Now he's saying there is a delay in getting AC to the site and he wants to use batteries, inverters, and Solar panels.

The application draws 1.25 A for a couple of seconds every couple of minutes. The whole load is 7.8 A-hr/day at 110 VAC (without allowances for dark, inverter load, etc). Now comes my confusion. When I'm sizing batteries I'm going to assume than an amp is an amp and I will need to provide a battery that can do 8 A-hr/day at 110V times allowances for the inverter, for dark, and for clouds (140W) and not some other calculation that gives me numbers between 0.4W and 275W.

David

 

[MikeHalloran]

Beware of actuator starting currents.
You need to learn the current draw for the first few milliseconds, because your system has to supply it.





Mike Halloran
Pembroke Pines, FL, USA

 

[zdas04]

I've got that in my calcs, it seemed more important to the inverter sizing than to the battery or solar panel sizing (it is a really small portion of the amp-hour result).

David

 

[MikeHalloran]

Yeah, I thought so too, when I specified a 12V DC actuator that nominally drew about 10 amps. They were declared dead at incoming inspection, because the laboratory supply used to test them folded back and wouldn't deliver the 300 amps they needed to start, unloaded.

Even better, our sparky wizards designed their own power supply instead of buying one. That wouldn't start 'em either. The customer demanded and got a battery and charger instead.



Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

Don't forget that the inverter has to sit there on ready standby -running- allll day waiting for its few seconds every few minutes.

You need to understand the standby impact. This will likely increase the energy demand by something like 10X.. Think 80Ahrs or there abouts.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IRstuff]

Something looks funny to me. 7.8Ah/day *rms(110W) = 1.213kWh/day assuming it's all resistive load. That would mean you need closer to 100 Ah/day from your battery, plus losses.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize