High Torque Low Speed Motors - PMSM

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Time for change
Today’s industry places high demands on innovative solutions and use of changing technology. The aim is to achieve not only increased productivity , reduce energy costs and machine availability, but improved energy efficiency and reduced operating costs as well. These demands can never be met with high-maintenance gearboxes, standard induction motors, and hydraulic systems – all of which are extremely inefficient. Investing in direct drive technology using HIGH TORQUE LOW SPEED Permanent magnet Synchronous motors / DIRECT TORQUE MOTORS instead of these conventional design approaches could greatly benefit in terms of costs and efficiency. Below are the applications and advantages what direct drive technology has to offer.

HIGH TORQUE LOW SPEED Permanent magnet Synchronous motors / DIRECT TORQUE MOTORS are used in :

  • Pharmaceutical machinery --- RMG, Tablet press
  • Gearless Elevators
  • Extruders
  • Painting and Packing machines
  • …….Wherever gearbox can be eliminated

Advantages of HIGH TORQUE LOW SPEED Permanent magnet Synchronous motors / DIRECT TORQUE MOTORS in Direct Drive Technology

Conventional systems commonly have a mechanical transmission which can consist of gears, gearheads, belts/pulleys or cams connected between the motor and the load. With Direct Drive (HIGH TORQUE LOW SPEED Permanent magnet Synchronous motors / DIRECT TORQUE MOTORS ) technology, the mechanical transmission is eliminated and the motor is coupled directly to the load. This results in added advantages as :

  • Direct connection to load increases torsional stiffness
  • Improved positioning accuracy
  • Backlash free operation
  • Highly dynamic load reversals without damaging components
  • Low audible noise
  • No maintenance for lubrication

Why Use Direct Drive / DIRECT TORQUE MOTORS Technology?

Increased Accuracy and Repeatability
The increased accuracy and efficiency of direct drive technology results in a higher quality product out of the machine:
Better Control
Torque and current have direct relation and so torque can be easily determined and c ontrolled
Improved Reliability and Zero Maintenance
Gears, belts, and other mechanical transmission parts break. By eliminating these parts and using direct drive motors, the reliability of the machine is improved. Gearheads require periodic lubrication and/or replacement in aggressive start/stop applications. Belts require periodic tightening. There are no time-wear components in a direct drive motor and consequently they require zero maintenance.
Fewer Parts
With direct drive motors / DIRECT TORQUE MOTORS, all you need is the motor and the mounting bolts. This often replaces many parts including brackets, guards, belts, pulleys, tensioners, couplings, and bolts, resulting in:
  • Fewer parts on the BOM. Less parts to purchase, schedule, inventory and control, and less parts to assemble.
  • Assembly time of the servo drops from several hours with the mechanical transmission to several minutes with the DDR.
  • Reduced cost. Although a direct drive motor may carry a small price-premium compared to a motor/gearhead with the same torque, consider that there is an overall cost reduction when eliminating the parts and labor of all the extra components required in a system with mechanical transmission.
High starting torque gives inertia advantage
Inertia matching limitations of mechanical transmission systems often force machine designers to use a larger motor than would otherwise be required just to satisfy the inertia matching requirement. Such sizing conventions are not required with direct drive technology.
Reduced Audible Noise
Machines with DDR motors have audible noise levels less than the same machine with a mechanical transmission.

Direct Drive / DIRECT TORQUE technology uses HIGH TORQUE LOW SPEED Permanent magnet Synchronous motors with feedback. The features of such a motor as compared to an induction motor are as below :

  • Permanent Magnet Synchronous motor are capable of producing very high starting torque @ 300% of Rated Value.
  • Current drawn by Permanent Magnet Synchronous motor is directly proportional to torque. You can calibrate / estimate machine torque directly from current reading. This is not possible with Induction Motor.
  • Permanent Magnet Synchronous motor speed range is 0 – 150 or 0 – 300 RPM with Full Rated Torque depending on machine requirement. There is no necessity to use a Gear Box.
  • PMSM has high efficiency of @ 85 to 90% whereas Combined efficiency of Induction Motor & Gear Box is @ 75%. (Gear Box 0.9 X Motor 0.83 = 0.75) .Thus will result in considerable saving in power consumption.
  • Generally cost difference in PMSM & Induction Motor with Gear Box is recovered by power saving over a period of 1 to 1 ½ years with two shift working.
  • Use of PMSM eliminates Gear Box noise, oil leakages, noise pollution etc.
MOTOR CHARACTERISTIC CURVES