Soft starts not only reduce the amount of current, it can also control how long it takes for the motor to get up to a particular voltage.
Start ramp is the time from when the soft starter begins to ramp up the voltage until full voltage is finally reached. The time is takes to ramp up the motor should not be very long, as a prolonged start may result in unnecessary heating of the motor and a risk of the overload relay tripping.
An unloaded motor will have a shorter start time than the set ramp time, but if the motor has a heavy load, the start time will become longer.
While soft starts do control ramp up speed, it is not precise. If precision is needed, then use a variable frequency drive, which TEMCo also provides.
Soft starts that a contain a kickstarter function are able to provide an extra pulse of torque, which is sometimes required to overcome the initial friction of jammed conveyor belts or pumps, for example. An activated kick start gives the necessary torque that will allow the application to break loose and the start ramp will then still provide a soft start.
This feature is good for overcoming stiction of high-friction loads.
Some applications do not have to have fast deceleration times but need the deceleration to be controlled.
In most cases, the speed ramping capabilities that soft starts have can be used to control the lowering of voltage as well, but for faster stopping,some soft starts can also provide braking. Soft braking can be used to reduce the time it takes for the motor to go from coast to rest.
Another technique that soft starts use is DC braking, which involved putting DC voltage into an AC motor winding.
Soft braking leads to less heating of the motor than DC braking, gives the motor more braking torque and is more useful for high inertia loads.
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