Overview
The WEG W21 is a proven, globally recognised three phase AC induction motor platform built around a heavy-duty FC-200 cast iron frame. Covering IEC frame sizes 63 through to 355M/L with power outputs from 0.12 kW to 315 kW, the W21 is designed to handle everything from simple fan and pump duties through to demanding process lines and crusher applications.
All W21 motors are rated for 415 V, 3 phase, 50 Hz supply with generous voltage and frequency tolerances of ±10% on voltage, ±5% on frequency and ±10% combined variation. They are also rated for continuous operation at ambient temperatures up to 50 °C — a practical advantage for Australian conditions where standard 40 °C rated motors may not provide sufficient thermal margin during peak summer temperatures.
The motors are supplied with six terminals as standard, suitable for both direct-on-line (DOL) and star-delta starting. Motors below 1.5 kW are internally star-connected with three terminals. Minimum pull-out torque across the range is 210% of rated torque, with starting current limited to six times rated current.
Key Features
The W21 platform uses WEG’s proprietary WISE (WEG Insulation System Evolution) insulation system, which combines enamel wires rated to 200 °C with a continuous flow solvent-free resin impregnation process. This system delivers Class F insulation performance while the motor operates with a conservative Class B (70 K) temperature rise. The 25 °C thermal margin between the design temperature rise and the insulation class limit means the motor can safely deliver up to 15% above rated output before reaching the Class F temperature ceiling, providing a built-in safety factor for overload conditions or high ambient temperatures.
The WISE insulation system also makes the W21 inherently suitable for variable frequency drive (VFD) operation without additional output filters, provided the drive switching frequency remains at or below 5 kHz and peak terminal voltages stay within the specified limits for the rated voltage tier.
Cast iron construction extends across the frame, endshields, terminal box and fan cover (on frame 160 and above), providing superior heat dissipation, corrosion resistance and mechanical strength compared to aluminium alternatives. All endshields include automatic drain plugs for condensation drainage, and triple grounding lugs are fitted as standard — one inside the terminal box and one on each side of the frame.
Construction And Design
The frame and endshields are manufactured from FC-200 cast iron with optimised fin spacing designed to maximise heat exchange while resisting dirt build-up in industrial environments. The terminal box is also cast iron with generous internal space for cable connections, and can be rotated in 90° steps to suit different cable entry orientations during installation.
Shafts are manufactured from AISI 1040/45 carbon steel as standard in frames 63 to 315S/M, with AISI 4140 alloy steel used in frames 315B and 355M/L to support heavy radial loads from belt-driven applications. Optional stainless steel shafts in AISI 316 or AISI 420 are available for corrosive environments.
Bearings are selected from the 62 series for smaller frames (63 to 100) and 63 series from frame 112M upward. Bearing life is rated at L10h 20,000 hours under maximum published radial and axial loads, extending to L10h 40,000 hours for direct-coupled arrangements free of external thrust loads. Sealed-for-life bearings are fitted in frames 63 to 132, with regreasable open bearings from frame 160 and above.
Variable Frequency Drive Compatibility
The W21 is designed for VFD operation out of the box. For motors rated up to 460 V, peak terminal voltage must not exceed 1,600 V phase-to-phase with a dV/dt limit of 5,200 V/µs. No output filter is required within these limits at switching frequencies up to 5 kHz.
For applications requiring extended low-speed operation under VFD control, forced ventilation kits are available from frame 90S upward. These kits replace the shaft-mounted fan with an independently powered blower, maintaining full cooling capacity at reduced motor speeds and eliminating the torque derating that affects self-ventilated motors at low frequency.
From frame 315S/M and above, insulated bearings or insulated endshield hubs combined with a grounding brush are recommended to prevent bearing damage from VFD-induced shaft currents.
Common Applications
The W21 range is widely applied across pumps, fans, compressors, conveyors, crushers, mixers, agitators, machine tools, water and wastewater treatment, mining and mineral processing, agricultural irrigation, and general industrial OEM machinery. The combination of a 50 °C ambient rating, conservative thermal design, IP55 protection and cast iron construction makes it particularly well suited to the demanding operating conditions found across Australian industry — from underground mining environments to outdoor processing plants and remote agricultural installations.
Selection Considerations
When selecting a W21 motor, confirm the required output power, speed (pole count), duty cycle, starting method, mounting configuration and ambient conditions. For altitudes above 1,000 metres or ambient temperatures exceeding 50 °C, derating factors must be applied to determine the available useful output. For belt-driven loads, check the published radial thrust limits against the calculated belt pull at the specified shaft position. For VFD-driven applications, review the torque derating curves at low frequencies and consider forced ventilation if the motor will operate continuously below 50% of base speed.
The W21 range is available across a comprehensive selection of IEC mounting configurations including B3 foot mount, B5 and B14 flange, B34, B35 and vertical V1, V3, V5 and V6 arrangements. IP56, IP65 and IP66 protection ratings, Class H insulation and tropicalised internal painting are available as factory options.
Support And Enquiries
Motordrives Australia supplies the WEG W21 three phase motor range across Australia. Our team can assist with motor sizing, frame and mounting selection, VFD compatibility, bearing configuration, shaft options and delivery scheduling. For technical support or a formal quotation, contact us with your application details.
