Soft Starters

Soft Starters are used on AC Motors to limit its starting current. The starting inrush current can be controlled by programming the Soft Starters. We can set the time taken by the motor to ramp up to full speed and thus protecting the motor from damage caused by sudden influx of power. Further, the mechanical stress on the motor, i.e. wearing of motor bearings, wear and tear of gear box is also reduced which results in savings on service and maintenance costs.

Soft starters are smaller in size than AC drives (VFDs) and hence you save a lot of space in Panels. Also this size difference is more significant if the Ampere ratings are higher.

Soft Starters are almost One tenth the price of a High Power Drive. So if your control requirements are covered by limiting current only at start and stop, with no need for constant acceleration and torque control, then there are significant savings to be won.

The soft starter does not change the frequency and therefore does not generate harmful harmonics. So when using a soft starter there is no need to consider harmonics at all as compared to AC drives (VFDs). No requirement of filters and screened cables.

The main difference between Soft Starters and VFDs is that a VFD can vary the speed of the motor while the Soft starter can only control the starting and stopping of that motor.

Different models of Soft Starters in Danfoss are :

• VLT® Soft Start Controller MCD 100 (0.1 KW TO 15 KW)
• VLT® Compact Starter MCD 201 / 202 (7 KW TO 110 KW)
• VLT® Soft Starter MCD 600(7.5 KW TO 1400 KW)

MCD 600 model of Danfoss Soft starter also has provision of an integrated bypass contactor in built to allow direct-online operations as an alternative. The integrated bypass contactor system offers multiple costsaving benefits – it ensures both extremely high efficiency and harmonic-free operation at full speed, reducing energy consumed and required cooling capacity.