SR Drive^® technology is ideally suited to the traction requirements of battery powered vehicles, providing an advanced yet cost effective solution for many applications. 

The key attributes SR Drive^® traction systems provide are:

• Brushless motor.
• Low cost motor & controller forming a system solution.
• Compact, rugged & reliable hardware.
• High torque and wide speed range.
  
• Very high electrical braking capability.
  
• Position sensorless operation.
  
• Smooth and operator friendly control.
  
• High energy utilisation efficiency.
  
• Fault tolerant with inherent fail-safe features.

Switched Reluctance Drives Ltd has many years of experience in the design of traction systems for battery vehicles, particularly at low voltage levels.  The integrated system design approach used to implement SR Drive^® technology solutions brings much benefit in cost and performance.

As an example, the motor and drive system shown was designed by SRDL for typical Class 3 pallet truck operation with a 24V lead acid battery pack.

The significance of the torque speed characteristic relates to the pallet truck’s 2 tonne payload and maximum speed of around 1.5 m/s.  This represents a significant momentum which, in the event of an emergency, requires a very large transient torque to bring the truck to rest in a short distance.  The worst case scenario is when the truck is being operated in reverse and the operator inadvertently backs themselves against a wall.  The handle to the truck is designed to actuate the emergency stop under these circumstances and the fully loaded truck must be capable of braking from full speed to rest in a distance comparable with the length of the handle such that the operator is not crushed.

The SR Drive^® system achieves this by providing a transient braking torque of between 5 and 10 times the continuous rated motoring torque.  Unlike conventional drives, the SR Drive^® solution was able to provide this emergency braking performance repeatedly without damage to the motor.

Operational testing on the truck confirmed excellent performance.  Hill climbing, braking capability and energy efficiency all comfortably exceeding typical DC motor based systems with the zero maintenance and the ruggedness associated with switched reluctance systems.  Recent advances in power semiconductors, signal processing controllers and position sensorless controls have only served to enhance the benefits of applying SR Drive^® technology to this type of application.

SR Drive^®  technology provides a world-beating solution across the whole range of small battery-powered vehicles including: Class 1, Class 2 & Class 3 materials handling trucks, golf cars and utility vehicles, AGV’s, tow trucks and many other similar applications.