The voltage class is one of the first decisions when selecting a VSD. A 220V-class drive and a 380/400V-class drive are not interchangeable simply because they have the same kW rating.
220V-Class VSDs
Some 220–240V-class drives are designed to accept single-phase input and supply a compatible three-phase motor at the drive's output voltage. This can be useful where three-phase mains is unavailable but the application uses a three-phase motor.
For example, Softcore Group Industrial Solutions currently lists a Delta MS300 2.2kW model with 180–264V single-phase input and three-phase output. That capability is model-specific and must not be assumed for every 220V VSD.
380/400V-Class VSDs
380/400V-class drives are widely used with industrial three-phase supplies and compatible three-phase motors. Softcore Group Industrial Solutions's industrial catalogue includes multiple 380V VSD ranges for pump, fan, conveyor and general machinery applications.
Check the Motor Winding Voltage
The motor's nameplate must be read carefully. Many motors show two voltage values with delta and star connection symbols. Those values tell you how the windings are intended to be connected. A VSD is not a universal voltage transformer, so the output voltage must suit the motor connection and winding rating.
Why Current Changes With Voltage
For a similar power level, lower-voltage systems generally require more current than higher-voltage systems. That affects drive selection, cable sizing, protection and installation requirements.
Can a Single-Phase Supply Run a Three-Phase Motor?
Yes, when a VSD model is specifically designed for the available single-phase input and provides the required three-phase output for the motor. The motor voltage, drive current rating and manufacturer limits must all be checked.
Do Some Drives Need Derating on Single-Phase Input?
Yes, depending on the drive family. Some manufacturers permit single-phase input only on specific models or require a larger drive/current rating. Always use the exact manufacturer instructions rather than assuming the same rating applies.
A Practical Planning Checklist
- Available supply voltage
- Single-phase or three-phase supply
- Motor nameplate photo
- Motor kW and rated current
- Motor voltage and delta/star information
- Application and load type
- Required speed range
- Indoor/outdoor and enclosure conditions
Technical Note
Final VSD selection and motor connection must follow the exact manufacturer's ratings, electrical design requirements and applicable standards. Incorrect voltage or winding configuration can damage equipment.
Related catalogue examples: Variable Speed Drives. For an equipment enquiry, contact Softcore Group Industrial Solutions at info@softcoregroup.co.za.