Thoughts On Running a Squirrel Cage Motor Above Its Rated Speed With A VFD

MC Thoughs On Running A Squirrel Cage Motor Above ITs Rated Speed ABB 1 400x275

October 26, 2022

 

Using a VFD To Run a Motor Above Base Speed:

How fast can my Variable Frequency Drive (VFD) run my motor? This is a frequently asked question and the answer requires consideration. There are power and mechanical limits that will come into play with the design and performance of a typical squirrel cage motor.

The VFD, itself, is usually capable of providing the necessary increased frequency. Actually, the VFD is capable of outputting 400Hz – 6.7 times the motors base design frequency.

Now look at some points to consider.

Sizing the VFD for Overspeed

Drives are designed and limited by current – both the motor and drive must be running below their rated currents before considering increasing the speed, and once the increase is applied that they still stay below these limits. So if you are going to overspeed an application, you may require oversizing the drive.

The type of load that is being powered is very important. If it is a fan or centrifugal pump, then the power will increase exponentially – a 2% increase in speed will increase the power consumed by around 6%. However, a constant torque load like an extruder would show a 2% power increase for a 2% speed increase.

MC Thoughs On Running A Squirrel Cage Motor Above ITs Rated Speed ABB 2 1024x467

Mechanical Equipment Considerations

Speeding up mechanical systems above designed limits will increase the mechanical stresses. With fans, recommended blade tip speeds may be exceeded or vibration levels may increase too much. A fan or pump will also create more noise with increasing speed. Electric motors and gearboxes all have a maximum design speed which should not be exceeded as well. All systems have resonant frequencies that you could experience as you go go above tested deign characteristics. You will need to be aware of these as they can be damaging to equipment.

Other Considerations

Above its rated speed, an electric motor enters the ‘constant power zone’ which means the available torque reduces with increasing speed. This is because the VFD can apply the higher frequency, but is limited to supplying the line voltage that is powering it. So you have to confirm if the reduced torque at the higher speed will still be sufficient to run the load.

#abb #motor #vfd #technology #automation

MC Thoughs On Running A Squirrel Cage Motor Above ITs Rated Speed ABB 3 700x464

 

Source

ABB Logo 300x150

 

 

 

 

Related Articles



Editor’s Pick: Featured Article

Weidmüller’s u-control 2000: The Automation Controller

Weidmüller’s u-control 2000: The Automation Controller

Weidmüller’s scalable engineering software, u-control 2000, adapts individually to your requirements. And, the u-control is powerful, compact and fully compatible with Weidmüller’s I/O system u-remote. This article looks at what makes u-control the heart of your automation.

Programmable logic controllers (PLCs) are one of the main components of any automated system. A typical control system has inputs, outputs, controllers (i.e., PLCs), and some type of human interaction with the system, a human machine interface (HMI), for example.

Read More



Latest Articles

  • Helping McMaster University Adapt its Buildings for the Future

    Helping McMaster University Adapt its Buildings for the Future

    February 22, 2024 McMaster University is using technology to better control and manage its legacy thermal systems and create smarter buildings McMaster University is using technology to better control and manage its legacy thermal systems and create smarter buildings. Carmichael Engineering Ltd., a Canadian systems integrator, worked closely with ABB Canada’s leading experts and its highly… Read More…

  • Grid Transparency Behind-the-Meter Is Key Challenge for Power Utilities, Study Reveals

    February 20, 2024 Siemens has released key insights into how electric utilities in the United States and Canada are managing the rapid adoption of behind the meter distributed energy resources (DERs) in its new report “Seeing behind the meter: How electric utilities are adapting to the surge in distributed energy resources.”  Data from the study… Read More…