Ive got a small compressor I'm gonna use to run a train horn and I need a power inverter that will push it does anybody know how many watts I should need?

 

The compressor should have a label that tells you the amperage or wattage required.

 

It's not an actual train horn compressor my uncle has a plasma torch compressor that we was gonna try to rig on my truck I have a 250 watt think it'd work?

 

The compressor should have a label that tells you the amperage or wattage required. Again.

 

Ok thanks probably don't have the label but oh well it's old

 

...or you could get a 12v compressor and not deal with an inverter. it'll run more efficient, and you can use less wiring. one less thing to go wrong.

also, 250 watts is not enough, assuming 120v. 500w is the bare minimum, 1000w is better.

 

Alright thanks I'll have to look into that you were actually some help compared to the other dudes

 

I don't think it's as simple as "watts." Watts is volts x amps, but done microsecond by microsecond. With resistive loads (lights) volts and amps are always in phase, but a compressor is a big inductive load, so the amps will be WAY out of phase (you will have a "power factor" less than 1.0). Put another way, a 120 watt light pulls 10 amps of 12 volts. But a compressor rated at 120 watts might have to pull 25 amps (out of phase) to get 120 watts. (Big inductive loads are often rated in "VA" (volt-amperes) instead of watts for this reason.)

Add to that the quirky inefficiencies of inverters, and figuring out the size of an inverter for a given wattage compressor is anything but trivial.

 

In addition, if the faceplate information does exist, it will state the running load of the motor. The starting load of the compressor is going to be much higher than that. Bottom line, running an 120V AC motor of any size from a 12V inverter is generally not a practical thing to do.

 

those guys have it right.

if you have air tanks, a cheap-ish 12v compressor will work significantly better than any 120v one.

 

Dont forget to use the correct size fuse or you will be roasting marshmallows by the end of the day over a open toyota fire.