The Star-Delta (Y-D) start-up is one of the most popular methods for limiting the inrush current of induction motors. However, what seems simple in theory often causes practical challenges when selecting the right protective equipment. A calculation error can lead to either “nuisance” tripping or, even worse, a burnt-out motor winding.
The Star-Delta (Y-D) start-up is one of the most popular methods for limiting the inrush current of induction motors. However, what seems simple in theory often causes practical challenges when selecting the right protective equipment. A calculation error can lead to either “nuisance” tripping or, even worse, a burnt-out motor winding.
In a Star-Delta system, the current flowing through individual components is not always equal to the motor’s rated current (In). It all depends on where the thermal overload relay (thermal) is integrated into the circuit.
If the protection is placed before the contactors, it “sees” the full current drawn from the network.
In professional Tripus systems, the thermal relay is usually mounted under the main contactor or the delta contactor. In this configuration, the current phase flows through the protection rather than the current line.
Incorrectly setting the relay to the full 10A inside the delta configuration means the motor could draw nearly 70% more current than it should before the protection reacts at all!
Selecting protection in a Star-Delta system leaves no room for error. Remember the 0.58 rule if you are mounting the relay inside the circuit. Following this principle ensures your machinery will operate reliably for years.
At Tripus, we offer fully assembled and tested Star-Delta control systems configured for specific motor power ratings. Don’t risk calculation errors – rely on our proven modules.
In case any technical questions our Technical Department remain for Your disposal
This will close in 0 seconds
This will close in 0 seconds
This will close in 0 seconds
This will close in 0 seconds
This will close in 0 seconds
