When selecting VSD’s the following should be considered:-
Load types and T-N Curve.
IP00, IP20, Cubicalised IP54.
• In coming Supply & protection.
Circuit breaker Protection. Customer responsibility, unless cubicalised.
• KW Power & Output Current.
For most applications, can be used for sizing the VSD.
• Overload and Rapid Acceleration/Torque
Overload 110% (Fan & Pump) to 150% for one minute.
Overload and accelerating torque (current) requirements, must be considered when selecting VSD’s. May result in a larger VSD rating.
• Rapid Deceleration / High Inertia
Need to consider dynamic braking unit and Brake resistors.
• Speed range. 0 - 650HZ . (Different for each unit)
Low speed operation and its effects on motor cooling and noise. Running above base speed and torque reduction.
• Speed holding accuracy.
Open loop (Sensor less) flux vector. 0.3% to 0.5%.
Flux vector control. Closed loop (encoder). 0.03%
RFI Filter (Input supply)
Output reactors, Filters.
• Motor Cabling.
Cable length. 20-30 meters.
Volts drop (Carrier frequency consideration).
Earthing and screening considerations. Safety & EMC.
Other VSD Main Features
- VSD & Motor Overload.
- VSD O/L trips Current > 150% of rated Current for 1 Min.
- Motor Electronic Thermal Overload.
- Torque Boost
- Slip Compensation
- S Curve.
- Energy Saving
- Simple PLC