Example: Driving a chain conveyor with a gear motor and VFD

If you’re starting from scratch with a new application, you have to determine how hard the motor needs to work to do the job.

06/12/2012


If you’re starting from scratch with a new application, you have to determine how hard the motor needs to work to do the job. Courtesy: SEW EurodriveInput data: A chain conveyor is to transport wooden boxes up a slope of α = 5° at a speed of 0.5 m/s. There is a maximum of four boxes each weighing 500 kg on the conveyor. The chain itself has a weight of 300 kg. The friction factor between chain and base is specified at μ = 0.2. A mechanical stop is mounted at the end of the chain conveyor which aligns the boxes before they are pushed onto a second conveyor belt. During this process, the box slides on the chain with a friction factor of μ = 0.7.

The application calls for a helical-worm gear unit that is frequency-controlled up to approximately 50 Hz.

Velocity: v = 0.5 m/s
Incline: α = 5°
Weight of transported material: mL = 2,000 kg
Weight of chain: mD = 300 kg
Friction factor between chain and base: μ1 = 0.2
Friction factor between box and chain: μ2 = 0.7
Desired acceleration: a = 0.25 m/s2
Sprocket diameter: D = 250 mm
Starting frequency: 10 cycles/hour and 16 hours/day

Calculating the optimum motor size depends on considering all the variables and following the right equations. For example, simply calculating the total resistance that the motor has to overcome involves the weight and friction of the conveyor itself carrying the load, additional friction when a box hits the stop, plus the efficiency of the gear unit itself attached to the motor.

Here is the calculation for determining the resistance force of the conveyor, half the weight of the chain, and the maximum load of boxes:

Here is the calculation for the additional resistance when a box hits the stop:

This is just the beginning since making a complete analysis of the application includes a number of additional factors:

  • Efficiency of the worm-gear unit
  • External moment of inertia
  • Load torque on the motor
  • Acceleration torque on the motor
  • Conveyor speed relative to motor RPM
  • Gear unit ratio
  • Service factor, and
  • Static power

Ultimately, once the conveyor is built and operating in real-world conditions, it will be a simple task to measure the performance of the motor and verify the accuracy of your starting assumptions.

The full set of calculations for this example can be found here.

In addition, another example has been provided, as well.



No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
Each year, a panel of Control Engineering editors and industry expert judges select the System Integrator of the Year Award winners.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Learn how to create value with re-use; gain productivity with lean automation and connectivity, and optimize panel design and construction.
Go deep: Automation tackles offshore oil challenges; Ethernet advice; Wireless robotics; Product exclusives; Digital edition exclusives
Lost in the gray scale? How to get effective HMIs; Best practices: Integrate old and new wireless systems; Smart software, networks; Service provider certifications
Fixing PID: Part 2: Tweaking controller strategy; Machine safety networks; Salary survey and career advice; Smart I/O architecture; Product exclusives
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control, and embedded systems.
Look at the basics of industrial wireless technologies, wireless concepts, wireless standards, and wireless best practices with Daniel E. Capano of Diversified Technical Services Inc.
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
This is a blog from the trenches – written by engineers who are implementing and upgrading control systems every day across every industry.
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Control Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.