Industrial application of Star Delta starter

Star Delta is categorize as a reduce voltage method

Reduced voltage methods are intended to reduce the impact of motor starting current on the power system by controlling the voltage that the motor sees at the terminals.

Common applications which require controlling the starting current or torque can be found in many industries including material handling, HVAC, mining, and waste water treatment where the main applications are fans, pumps, conveyors, and compressors.

This circuit allows the motor starter to initially connect the leads in a star connection for starting, and then reconnect them in the delta configuration for running

This method is usually employed on motors rated below 600V. Motors rated 2.3kV and higher are usually not suitable for Star-Delta starting. In term of power, it is suitable for motor rated above 7.5 Hp (5.5 kW)

Fans can be either directly connected to the motor or belted. The fans that are belted usually require torque control during starting to eliminate or reduce excessive belt wear as a result of slippage during across the line starting.

Pumps have low starting torque profiles. The initial torque and acceleration torque can be critical in some pumping applications and is usually determined by the design of the pump. Some pumps such as those with long shafts connecting the motor to the pump, may be damaged if the starting toque is too high.

some types of compressors need low torque to accelerate to full speed. Reciprocation compressors require high starting torque especially when starting under load. Other types such as centrifugal and axial vane type require low starting torque because of the design characteristics.

The need to limit the inrush current may be due to government mandates, power company restrictions, distribution system limitations, or operation in areas that are adjacent to or within a residential area may need to limit current during starting to eliminate voltage drops that cause light flicker.

A good example of this is on pumps for hydraulic elevators in an apartment complex. These pumps have low starting torque requirements, so limiting current during starting minimizes any line sags that would have occurred if the pump was started direct on line.