Comparison of different motor starting techniques


#1

RVSS (Reduced Voltage Soft Start)

Advantages -
Potentially low cost
Soft Mechanical start

Disadvantages-
May not be able to meet starting torque requirements.
May not meet interconnect requirement
Produce Harmonic

VFD Start

Advantages-
Provides near rated torque at starting
Soft mechanical start
Meets utility voltage sag/inrush limits

Disadvantages-
High installed cost
Produce harmonics
Complexity of equipment
May require cooling equipment
Synch transfer controls
Requires M+1 additional motor starter

Capacitor Assisted Motor Start

Advantages-
Provides near rated torque at starting
Meets interconnect requirement
Lower cost
Simplest to install and maintain

Disadvantage-
Does not provide a soft start function for mechanical loads that require it.