asynchronous induction motor

DL 1021 Induction motor with three-phase stator winding and squirrel cage buried in the rotor. Technical features:

• Power: 1.1 kW
• Voltage: 220 / 380 V Δ/Y
• Current: 4.3 / 2.5 A Δ/Y
• Speed: 2870 rpm, 50 Hz

my question is what does it means for voltage i.e 220/380 V Δ/Y. i did not get the idea Δ/Y(is that starting method or what?

In this case it's not about the starting method. That data plate is telling you that if you HAVE a 380V (nominal) supply, you use the Star motor connection pattern and if you HAVE a 220V supply, you use the Delta motor connection pattern. You will see that in more detail inside of the connection box cover or wherever the wiring diagram is located.

So if you are using this motor on a 220V supply and connecting it in the Delta pattern, the motor Full Load Current is going to be 4.3A. If you are using it on a 380V supply and connecting it in the Star pattern, the FLC is going to be 2.5A.

• You should probably explain the relationship between the voltages and the currents below them. Commented Mar 16, 2018 at 23:30

380 volts is $\sqrt3$ times higher than 220 volts and if you wire your induction motor stators in star formation they receive a phase voltage of 220 volts from a line voltage of 380 volts: -

So if Vab is 380 volts then Voa is 220 volts (due to basic trigonometry).

is that starting method or what?

For a lot of induction motors, they will connect the stators in delta to start the machine (higher starting torque) then automatically switch to star formation when running.

I'm not saying that this is definitely what your motor is designed for of course. Read the data about it.