Disappointed that my ancient Mod Sine Wave inverter (140W cont, 200W surge) shuts down with a 120W coffee grinder. Works ok with the 400W (cont) MSW inverter built-into the truck, though a little slow.- Do AC motors work better with pure sine wave?- What sort of surge Watts do you expect from a motor? Double the cont. wattage?Anyway, guess I'm in the market for a new, more powerful inverter ...

From Wikipedia:Sine wave inverters with more than three steps in the wave output are more complex and have significantly higher cost than a modified sine wave, with only three steps, or square wave, (one step), types of the same power handling. Switch-mode power supply (SMPS) devices, such as personal computers or DVD players, function on quality modified sine wave power. AC motors directly operated on non-sinusoidal power may produce extra heat, may have different speed-torque characteristics, or may produce more audible noise than when running on sinusoidal power.From me: Surge wattage can be up to 4 to 5x running wattage.

Try the smaller inverter with fatter wire to the battery. If using the RV 12v socket, that can only handle about 8 amps DC maybe 90w due to its thin wires.ISTR the 12v sockets in trucks and cars are heavier duty than the 12v sockets in an RV usually are.

NOTHING is designed to work on MSW.If it works on MSW great. Poor performance in general should be expected.

Starting current depends on the kind of motor (and its load, etc.) If it's a shaded pole induction motor, which would be my guess, it's probably not too much different than the operating current. Do note that the power factor could be somewhat poor, so the 120W motor could consume more than 120 VA.How well the motor functions on a non-sinusoidal power input also varies with the kind of motor. An induction motor typically will have somewhat lower torque (and hence speed) and run somewhat less efficiently (warmer), but not unreasonably so unless it's sized very marginally for its task or run for very long periods of time (or both). A universal motor with brushes will be relatively little affected by the differing waveforms.BFL's suspicion that the inverter is shutting down from undervoltage at its input rather than overcurrent at its output has merit. I think most inverters—at least inexpensive ones—are mainly protected from excess power draw by the DC input fuses. I may well be wrong.

2oldman wrote:From Wikipedia:Sine wave inverters with more than three steps in the wave output are more complex and have significantly higher cost than a modified sine wave, with only three steps, or square wave, (one step), types of the same power handling. Switch-mode power supply (SMPS) devices, such as personal computers or DVD players, function on quality modified sine wave power. AC motors directly operated on non-sinusoidal power may produce extra heat, may have different speed-torque characteristics, or may produce more audible noise than when running on sinusoidal power.From me: Surge wattage can be up to 4 to 5x running wattage.Ok, maybe 800-1000W surge for the coffee grinder. That's probably what the truck's 400W continuous puts out. Then there's the ~200Whand blender ... and going to pure sine wave ... not cheap. BFL: the 12V socket is one I wired myself with rel. heavy wire and 10A (?not sure) fuse in the WFCO. Only about 1' from WFCO. Still, if the surge is 1000W at 13V, that's 76A. But the fuse didn't blow; maybe slower response than the old inverter's overload circuit?Guess it would be best to get a pure sign wave inverter and wire it close to the batteries. For a coffee grinder? sheesh ...

Small AC motors and Inverters | Good Sam Community

110 Replies

Chandalen
Explorer
May 16, 2015
I thought about 'whole home' but we have kids, and I was thinking if they had access to any plug for power... it could be a bad day. We stuck with 3 active plugs in the camper so we know what the kiddo's are up to.
MrWizard
Moderator
May 16, 2015
do NOT use the branch circuit FEED Back idea
those are double ended male cords, and are called "Suicide Cords"

the ems will have no problem with inverter power, and there is nothing wrong with a few seconds delay, in power coming on
pianotuna
Nomad III
May 16, 2015
Hi,

I'm sure that Canadian Tire would be more than willing to sell to a USA person. But, by the time you pay for shipping, you may as well buy a Pro-Watt from bestconverters.com
pianotuna
Nomad III
May 16, 2015
Hi,

Idiot proof is plugging the shore power cord into the inverter.

The ems will be quite happy to be "fed" by the inverter.
brulaz
Explorer
May 16, 2015
pianotuna wrote:
Hi,

For 1000 watts I'd not be opening the case up.

I do whole house all the time.

Thanks. I won't open the case, just plug it in then.

With respect to "whole house", that would certainly be the easiest, and the electrical sockets would be conveniently located.

Was only planning to turn on the inverter when needed, probably just a few times a day (unless we become dependent upon it:)). That would save on the parasitic drain (~0.6A) of the inverter, and on any 110V parasitic drains, like in the Microwave.

But I have an EMS-LCHW30 surge protector installed inside the trailer. Not sure if I want the inverter output going through that (more losses? Will the EMS even accept the power?). And the EMS has a delay built into it, currently 136s, but that can be reduced to 15s. So every time I turned on inverter, there would be 15s delay before power came on. Maybe should have got the portable EMS instead.

Alternatively, to get around the EMS, could I feed the inverter's 120VAC into the distribution panel via a secondary branch circuit? That actually would be more convenient as there's an outlet on a 15A breaker close to where I want to put the inverter.

That should feed all the other 120VAC branch circuits and stop at the EMS relay (would have to check with Prog. Ind. about that).

And then when I forget about that connection and plug into shore power ... wonder what the inverter would do? Sounds exciting and doesn't seem that idiot proof.
Naio
Explorer II
May 16, 2015
Is there any way for us US folks to get one of these mail order? Without driving to Canada?
jolooote
Explorer
May 16, 2015
Don't ya just hate engineers? Y can't they just answer a question? LOL
pianotuna
Nomad III
May 16, 2015
Hi,

For 1000 watts I'd not be opening the case up.

I do whole house all the time.
brulaz
Explorer
May 15, 2015
BFL13 wrote:

...
You can go "whole house" by plugging your shore power cord into it (via adapter) Turn off the converter though. Also fridge and water heater to be on gas only. (Fridge not on auto but on gas)
...

Was wondering about that. It's very tempting.

My old trailer's water heater had an on/off switch right on it. This new one ... don't recall seeing it. Seems automatic. Perhaps at the breaker panel ...
BFL13
Explorer II
May 15, 2015
The 1000w isn't very noisy. You can go "whole house" by plugging your shore power cord into it (via adapter) Turn off the converter though. Also fridge and water heater to be on gas only. (Fridge not on auto but on gas)

The remote's green ON light is hard to see. You can put a "night light" in a receptacle to show you the inverter is on. I use my three-light tester for that job.

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Small AC motors and Inverters

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