Can I run a single phase motor off a car battery & inverter?

You need to determine if the 250 W motor rating is the electrical input power or the mechanical output power. Motors that are manufactured to international standards have power ratings marked on the nameplate that are the mechanical power that the motor can deliver to a load for continuous operation. Small single phase motors are not very efficient, The input power is likely to be twice the output power.

An AC motor's current is input watts / (volts X power factor). The full load power factor is likely to be between 0.6 and 0.8.

The motor will likely require 20 to 25 amps for a second or so during starting. The inverter will not be able to supply that much current even for a fraction of a second unless it is designed for a motor load.

Re Additional Details

The motor in question is a three-phase motor. The nameplate marking “Delta/Y 230/400 V” means that the motor is rated for 230 volts for the 3-phase delta connection and 400 V for the 3-ph Y connection. I doubt that you will find an inverter with 12 V DC input and 230 V three phase output.

You can easily find a variable frequency drive (VFD) inverter that will operate the motor. It should be fairly easy to find a VFD with 230 V single-phase input and 0-230 V, 0 – 50 Hz, three-phase output. You may be able to find a VFD that will accept a 325 V DC input. A VFD will start the motor at a low frequency so that the starting current can be limited to 1.37 to 2.1 amps.

The 0.25 kW marking on the nameplate is the mechanical power output rating. The rated input current is 1.37 A for the 230 V connection. The input VA rating is 230 X 1.37 X 1.732 = 546 VA. That is the apparent power. The real power is 546 X .75 = 410 watts. The power factor, 0.75, is marked after the Greek letter Phi on the nameplate.

How much continueous time you want to run the motor. Assume one hour. Then the battery must store 250 Watt hour at least. Assuming a 12 Volts car battery, you will require 250/12 = 20 AH nearly. Taking efficiency into consideration, you may require 40 AH battery capacity which is usually for a heavy truck. Then you must have a charging system for the battery.

Assuming no power losses in the inverter, a 240v motor of 250W will draw about 21A from the battery ( 12 x 20.8 = 240 x 1.04) from Ohms Law.

A standard heavy duty battery is about 100Ah, so you can run it if you've got big enough cables, but only for about 5 hrs max.

1. The motor will draw a short term 'starting surge' which

will exceed the capacity of your inverter when it starts.

(This is typically considered as 225% of the running current.)

Will your inverter supply/withstand this short term overload?

Read the 'spec.'s.

2. 250W + inverter losses will be about a about a 25A. load

on that 12V. battery.

Expect about 80% of the Amp./Hr. rating of the battery as

maximum motor running time per full recharge.