VFD Sizing Guide: Nameplate to Model

The motor nameplate

The nameplate prints, among its data: rated power (kW), rated current (A) at the connection voltage, and rated frequency/speed. Two motors of the same kilowatts can print different rated currents, and the published model tables give current beside power where the table carries a current column — for example the AU320's single-phase-input rows run 3.8 A at 0.75 kW to 20 A at 5.5 kW. (Not every published table does: the YSG solar example table lists panels, voltage and power without a current column.)

Rated current and the overload classes

On the series whose tables carry a current column, the tables print each model's rated output current beside its power. Where a series publishes two overload classes, the classes themselves are printed numbers: the EV510 and AU1000 publish G type at 150% of rated current for 60 s (180% for 3 s) and P type at 120% for 60 s (150% for 3 s). Which class a given duty takes is not printed in the tables — send the motor and load data with your enquiry and ask for the class for your duty to be stated in the quotation.

The supply classes

Published input class	Series and published figures
Single-phase 220 V input, three-phase output	AU320 S1 rows (0.75–5.5 kW); EV200 S2 rows (0.4–2.2 kW); see the single-phase page
220 V input, 380 V output (boost)	AU400, 1.5–75 kW — see the AU400 page
Three-phase 380 V class	The mainline tables of AU720 (0.75–500 kW), EV510 (from 0.4 kW) and AU320 G3 rows
Higher voltage classes	EV510 publishes 480 V, 690 V and 1140 V model classes

Environment and options

Placement: protection grades and mounting formats are published per series; the sealed formats are covered on the waterproof page. The options an application states in its enquiry can include a braking unit (built in at documented power bands — 18.5 kW and below on the AU720, 1.5–22 kW on the AU400, above 3.7 kW on the EV200), an encoder card for closed loop, or a fieldbus for the line controller — state the ones your installation uses in the enquiry and ask for them to be covered in the quotation. For the commercial side of selection, the buying guide covers the same checklist from the procurement side.

Frequently asked questions

Can I size by kilowatts alone?

On the series whose tables carry a current column, the model tables publish both figures — kilowatts and rated output current per model — and the motor nameplate prints its rated current beside its power. State both in your enquiry and ask for the model against them to be stated in the quotation.

What do the published derating bands mean for frame choice?

The published bands state the conditions against which the check is made: the starting or shock-load profile of the duty, and installation conditions outside the published bands — the AU720 documentation, for example, publishes an ambient temperature range of −10 °C to +40 °C and derating for installation above 1,000 m altitude. For a given application, ask whether it takes the heavier class or a larger frame to be stated in the quotation.

Does the guide apply to pump and solar drives?

The published figures are the general ones. Pump-specific functions are published for the pump drive range and solar model selection for the solar range — see the pump VFD and solar pump inverters pages.