Control of motor speed hence rate of application of force to test specimen.

The rate of force application to a test specimen is usually dictated by the test standards being complied with. The specification for crimped joints (connectors) for aircraft electrical cables and wires BS 5G 178-1:1993 states the jaws clamping the test specimen shall seperate at a steady rate of 25 mm/min to 50 mm/min. Other standards such as EN61238-1:2003 (connectors for power cables) are more stringent and will be discussed later.

The speed of the test stand platform is determined by the drive motor and the mechanical gearing. The gearing is fixed at design leaving the motor speed as the controlled variable. The DFTS5000 series of test stands uses a three phase motor to apply load, with the voltage and frequency provided from a variable frequency drive. It is the VFD which is configured and controlled from the PC/Laptop/Tablet via a serial connection.

VFD speed control of AC Motor

Digital speed Control

The VFD-EL series used has an industry standard RS485 physical interface and provides both MODBUS ASCII and RTU protocols, making it compatible with a host of test software. Demonstration LabVIEW VI’s are available.

Control Panel Software