Star delta starter timer circuit diagram

Star delta starter timer circuit diagram

Star Delta 3-phase Motor Automatic starter with Timer

From L1 The phase current flows to thermal overload contact through Fuse, then OFF Push button, On Push button Interlocking Contact 2, and then C3. This way, the circuit is completed, as a result;

Most induction motors are started directly on line, but when very large motors are started that way, they cause a disturbance of voltage on the supply lines due to large starting current surges.

Star delta starter timer circuit diagram

How to setting the timer for star delta starter?

Set the stop watch and measure the time from starting (0 rpm ) until it reach 80% of motor speed.example if full motor speed is 1400  rpm,so for 80% full speed is around 1,120 rpm.So stop the watch and take the time reading.


A 3 Phase Induction motor consists of a stator which contains 3 phase winding connected to the 3 phase AC supply. The arrangement of the winding is so as to produce a rotating magnetic field. The rotor of the Induction motor contains cylindrical core with parallel slots that contain conductors.


Readymade kit is a ready to use project ensuring 100% output guarantee, fully supported by elaborate documentation and audio visuals. Suggested for beginners who want to explore practical application without worrying about the hardware.

Star delta starter timer circuit diagram


On energisation, the star contact closes instantaneously during the timing period T. At the end of the timing period, the star contact opens. At the end of the timing period Ti (interswitching time), while the contact is open, the delta contact closes and remains in this position.


Example: An LC1-F185 contactor supplied with 115 V-50 Hz for a consumption of 55 VA or a current consumption equal to 0.1 A and cos ϕ = 0.3. For 0.1 A, curve 1 indicates a durability of approximately 1.5 million operating cycles. As the load is inductive, it is necessary to apply a reduction coefficient k to this number of cycles as indicated by curve 2. For cos ϕ = 0.3: k = 0.6 The electrical durability therefore becomes:1.5 106 operating cycles x 0.6 = 900 000 operating cycles.

Star delta starter timer circuit diagram

Star Delta starter for a three-phase asynchronous motor

By connecting the armatures of the motor in star they are subjected to the line-to-neutral voltage (230V). By connecting them in a triangle they are subjected to the line-to-line voltage (400V); intuitively the current consumption and the torque will be lower for star connection.