Compact soft starts as small as 45mm wide, rated at up to 5kW motor power, have been added to ABB Control’s PS product range. An 11kW unit measures just 90mm wide.
ABB has also launched new larger PS soft starts rated at up to 75kW.
Soft starts reduce mechanical stress and thus increase life expectancy of motors in hoists and conveyor cranes.
The DIN-rail-mounted PS soft starts use purpose-designed thyristors that stay cooler in use and have a built-in bypass for the ramp circuit when the voltage reaches 90% of the nominal maximum value.
ABB says that these features mean there is no need for add-on bypass circuits or for large heat sinks or fans, saving space in the control panel.
In spite of their compactness (ABB claims that they are ‘among the smallest available’), they feature a built-in stop ramp function, which is usually only provided as an add-on unit.
They are installed with power and power out wires and two wires for on/off control. There is an LED display for fault diagnosis, and three potentiometers on the front of the panel set the initial voltage, the ramp up (start) and ramp down (stop) time.
The larger PS range of soft starts, for motors rated at between 7.5kW and 75kW, have an optional current-limiting function for motor protection and built-in miniature cooling fans rather than large heat sinks. They also feature front panel controls for ramp times, initial voltage and current limit set-up.
