when do you use a soft starter instead of a drive

Feb 17, 2019

Here are some common applications of each


 Soft Starters


Application with low or medium starting torque*

Lightly loaded applications*

Little or no speed control during run mode*

Reduce mechanical wear and damage to system*

Controlling inrush*

Power monitoring*

Drive

Single-phase applications on certain drives*

Speed control and system efficiencies operating at reduced speeds during the run mode*

Applications with high starting torque*

Continuous feedback for critical position control*

Holding rotor at zero speed*

Reduce mechanical wear and damage to system*

Starting Methods


?How does a Direct On Line (DOL) starter work

As a basic starting method, a DOL (or ‘Across-The-Line’) starter applies full voltage, current, and torque immediately to the motor once a start command is provided. Normally, power is immediately removed once the stop signal is given. On and Off are the only two states of this method. Optional smart overloads can add complexity to the starter and feedback from the starter. Figure 2 shows the typical NEMA Design B or IEC Class N motor torque and speed characteristics

?How does a soft starter work

.An algorithm controlling three pairs of back to back SCRs are used to start and stop the motor

The back to back orientation of the SCRs allows the AC voltage to be controlled by changing the firing angle every half cycle Figure 4. Voltage is either ramped up to full voltage, or is limited to provide current limit starts



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