Comparison of different motor starting techniques

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.