Vector/Inverter Duty Motors

Results per Page:

What is an Inverter Duty Motor

The terms ‘inverter duty’, ‘vector duty’ and ‘1000:1 turndown’ duty may be used interchangeably within the motor community, although these terms mean different things.

Inverter rated often refers to any motor with minimal turndown ratios, such as 10:1 turndown. Whereas 1000:1 turndown offers specific construction and capability. All 1000:1 motors are inverter duty, but not all inverter duty motors are 1000:1 turndown. 1000:1 turndown motors are used in applications where the motor shaft must spin incredibly slow.

What they do have in common is this. These motors provide constant torque, meaning they offer a consistent torque from zero to base speed when operated with a variable frequency drive (VFD). Inverter duty motors also have the ability to provide holding torque. This is when a motor can deliver its full rated torque output when at zero speed without suffering from damage due to overheating.

People are asking:

  • How to tell if a motor is inverter duty rated?
    • Because most motors are now inverter ready, it’s not always indicated on the nameplate. However, if you do see a turndown ratio listed on the nameplate (i.e. 10:1 or 40:1 or 1000:1), this indicates the motor is inverter duty. You may also see ‘CT’ or ‘VT’ listed on the nameplate (constant torque and variable torque, respectively), which is a sign that the motor is inverter rated.
  • What is the difference between inverter duty and general-purpose motors?
    • When an inverter duty motor is running substantially slower than the base speed, the motor will have reduced cooling efficiency. This is because the fan is powered by the motor shaft, and as the shaft speed decreases, so does the cooling ability of the fan.
    • Inverter duty motor wires will be rated for 1600-volt spikes, as they’re coated with high dielectric strength film.
    • Inverter duty motors will have insulation class F or H.
    • High temperature bearing grease will be required.
    • Insulated bearings are required for inverter duty motors.
  • What is the difference between inverter-ready and inverter-duty motors?
    • Most industrial motors made today are ‘inverter-ready’ motors, meaning they are suitable for use for use with VFDs. They can handle variable torque loads over a range of speeds. Whereas ‘inverter-duty’ motors have specific construction and capability. They have special spike resistant insulation systems.

Baldor Inverter Duty Motor

Baldor AC inverter/vector duty motors offer constant torque at zero speed. Baldor offers the stainless-steel vector duty motor for use in washdown applications.


  • 1/3 to 1000 horsepower
  • 1200 – 3600 RPM
  • TENV and TEBC enclosures
  • Cast iron, rolled steel, aluminum, and stainless-steel frame
  • 1000:1 constant torque

These are often used in winders, extruders, and oil drilling.

Marathon BlackMax Inverter Duty Motor


  • ¼ - 30 horsepower
  • 1200 - 1800 RPM
  • TEBC, TEFC and TENV enclosures
  • Cast iron, rolled steel, and aluminum frame
  • 1000:1 constant torque

These are often used in crane, conveyors, and pump applications.

Insulation Class for Inverter Duty Motors

Because VFDs can cause high-frequency voltage spikes in the motor windings, specific insulation is required with inverter duty motors. Class F or class H insulation is required when using inverter duty motors to protect the motors windings.

Where to Buy Inverter Duty Motors in Canada

Shop 1000:1 turndown motors online through our Canadian website today. With over 400 SKUs and convenient filtering options, you can easily find the motor you’re searching for.

eMotors Direct’s stock of inverter duty motors are used in industrial applications that require precision and performance from a compact and lightweight motor.

Our vector duty electric motor category covers a selection of motors with a 1000:1 turndown ratio. Choose a motor from fractional horsepower up to 1000 HP and a variety of frame sizes. Select a voltage input and RPM output rating that matches your intended application. Ensure you choose an enclosure type that will keep your motor’s internals safe from contamination, choose from ODBC, TEAO, TEBC, TEFC, and TENV. All available from your most trusted brands; Baldor, Leeson, Marathon, and Nidec.

Need a hand finding the right motor for your application or legacy replacement? Contact our motors experts. They have extensive knowledge, backed by over 45 years of experience, to help you with your electric motor project.

Related Articles