"Why all the pushback for wanting the assertions of abuse to be backed up by real data, or wanting confirmation from somebody who has expert status with motors?"
No push-back intended from me. My statement is based on my own experiences. Example, my Xantrex ProwattSW 2000 inverter will run my 800 RFwatt (likely about 1200w gross) microwave repeatedly without much regard to battery SOC (though I've never tried it below 85 SOC), but will not run a small 5.5a, 660w vacuum. The reason (in my view) is that the vacuum is more of an inductive resistance bearing load (likely 3-5 times the surge) than is the larger microwave. This doesn't even take into account the start-up power reqd for an A/C rotor or a high head pressure scenario. I only say this in reference to (your statement) an air cond being an easier start load than a 1000w microwave. Your statement seems to disregard the Air cond's surge...Please explain...
* This post was
edited 04/10/12 01:52pm by 3 tons *
For what its worth - I've ran two different 13.5 ACs with a my Honda 2000 for the last 7-8 yrs, never had a problem. Don't run for more than an hour or so at a time and not on eco. Quite a few hours total I'm sure. I'll keep doing it becuse it's better than listening to the DW complain she's too hot.
2011 Silverado 1500 LTZ/Trail Lite 8230
Since, by your own admission, you are not an engineer, it is going to be very difficult to offer an explanation that would satisfy you from an electrical engineering standpoint.
I AM an electrical engineer with no specialty whatsoever in motors. As an engineer I know that what seems like a perfectly logical premise often turns out to be the opposite of reality when the facts are known. The electrical engineering explanation is not enough. Things like the heat rise of the affected masses and mechanical issues are also in play.
I seriously doubt that a 1000w M/W draws more than an RV air cond...That is UNLESS the Microwave is experiencing a 'locked rotor' condition.
Having measured it, I seriously know for a fact that the 1000 watt Dometic branded microwave in my previous RV drew 12-1/2 amps at 120 volts, or 1,500 watts, while the 13,500 btuh Dometic standard efficiency air conditioner pulled 11-1/2 amps and about 1320 watts sitting in full sun on a 90+ day. Several others have reported similar measurements on the numerous "will an eu2000i run an air conditioner" threads over many years.
If the Wikipedia Motor Soft Starter Article is to be believed, "A motor soft starter is a device used with AC electric motors to temporarily reduce the load and torque in the powertrain of the motor during startup. This reduces the mechanical stress on the motor and shaft, as well as the electrodynamic stresses on the attached power cables and electrical distribution network, extending the lifespan of the system." and "Electrical soft starters can be any control system that reduces the torque by temporarily reducing the voltage or current input, or a device that temporarily alters how the motor is connected in the electric circuit." This is not talking about a hard start cap, a totally different device. Soft start and hard start terminology is often incorrectly used on the forum.
Why all the pushback for wanting the assertions of abuse to be backed up by real data, or wanting confirmation from somebody who has expert status with motors?
2009 Fleetwood Icon 24A
Honda Fit dinghy with US Gear brake system
LinkPro battery monitor - EU2000i generator
I am speechless! My specialty isn't AC power either but the university I went to wouldn't let me graduate without understanding the principles of operation of the different types of electric motors. This stuff isn't complicated. It is rudimentary.
First of all, I don't think you understood the content of the links you provided. The Cummins link illustrated and discussed relatively complex solutions precisely because the "capacitor" solution in the original post is not satisfactory. Notice there are no capacitors in any of the example circuits. These are "soft start" solutions whereas increasing the value of the start capacitor actually has the opposite effect. Soft start circuitry isn't appropriate for this application anyway because the starting torque for a compressor motor precludes that. This is mentioned in the first paragraph of the Cummins article.
I don't trust a DVM to correctly read a fast-moving value. So I'm not convinced the voltage actually went to 59, and I'm honestly surprised that it recovered to 120 so quickly. For measurements like that I drag out the scope or analog meter. All of this I believe is irrelevant to the motor abuse issue.
You are right to distrust a digital meter but if it is in error, it is going to be on the side of missing an even more drastic drop in voltage. If the guy's meter read 59, it is probable that the voltage went much lower for a short time.
The voltage isn't really that relevant. It is the transient current he should have been watching.
No push-back intended from me. My statement is based on my own experiences. Example, my Xantrex ProwattSW 2000 inverter will run my I only say this in reference to (your statement) an air cond being an easier start load than a 1000w microwave. Your statement seems to disregard the Air cond's surge...Please explain...
I was specifically responding to "I seriously doubt that a 1000w M/W draws more than an RV air cond...", and not addressing startup current, which I don't have a measurement for. I can say that the eu2000i struggled longer starting the microwave but that's hardly scientific. In one case the generator is getting hit with a stopped motor, and in the other case with a discharged capacitor. It's pretty difficult to measure the startup power and I don't have either of the devices any more anyway. The eu2000i does start my current 15,000 btuh air conditioner without a whole lot of fanfare on a moderate temp day but after a few minutes of running the watts creep up past 1,600 so that's an infeasible combination. I didn't want to muddy the waters with another issue: Unless demonstrated otherwise, I don't trust a DVM to correctly read a fast-moving value. So I'm not convinced the voltage actually went to 59, and I'm honestly surprised that it recovered to 120 so quickly. For measurements like that I drag out the scope or analog meter. All of this I believe is irrelevant to the motor abuse issue.