Exhaust Fan System for Fire

4 x 18.5kW Exhaust Fan

Star-Delta Closed Transition Starting

The above panel uses a star-delta closed transition method to start the 18.5kW motor, the one at the bottom right is the resistors used for the closed transition during star-delta changeover. The resistors serves to smoothen the voltage curve during the changing of star to delta. For more explanation about this starting method, you can refer to this website : Star-delta motor starter explained 

Existing system problem

The existing system is faulty and the exhaust fans are unable to start when a fire signal is triggered. This could be due to lacking in maintenance of the system as it is ideal for building personnel to run their equipment at least once every 3 months. This kind of starting method is also rarely used nowadays due to the increased used of power electronics (solid-state relays) for such a system.

Solid-state relays in Soft starters are better and much safer than the star-delta closed transition, as the resistor will heat up a lot during transitioning. Below is the upgraded system with Soft-Starter.

Upgraded 4 x 18.5kW Soft-Starter System

Benefits of using Soft-Starter

Above shown is a PSTX model of a soft-starter by ABB, this is the higher end soft-starter that we use for bigger motor sizes such as in this application. For this system, the user is able to see the pump running current on the HMI display outside the panel. System fault history and motor total run time are displayed on the screen as well.

Both of them are reduced voltage starting methods, however soft-starter is the more popular option nowadays due to the price and availability. Soft-starter also comes with many other practical functions such as motor coil heating etc.