No abstract

In a ballast circuit, the piezoelectric transformer (PT) is used to replace the conventional inductor-capacitor resonant tank saving valuable space and cost. During circuit operation, a very high voltage is required to initially ignite the lamp while during sustained operation the voltage requirements are significantly reduced. With ballast in mind, a design process has been developed to optimize a radial mode piezoelectric transformer or Transoner ® to fit a specific application while simultaneously providing highly efficient performance and the capability to provide ZVS to the switches. The design procedure was verified by a custom-designed PT operating in a 32-W ballast.

In a ballast circuit, the piezoelectric transformer (PT) is used to replace the conventional inductor-capacitor resonant tank saving valuable space and cost. During circuit operation, a very high voltage is required to initially ignite the lamp while during sustained operation the voltage requirements are significantly reduced. With ballast in mind, a design process has been developed to optimize a radial mode piezoelectric transformer or Transoner ® to fit a specific application while simultaneously providing highly efficient performance and the capability to provide ZVS to the switches. The design procedure was verified by a custom-designed PT operating in a 32-W ballast.

No abstract

The Tokamak Fusion Test Reactor (TFI'R) electric power systems include two motor generator (MG) sets that supply pulsed power to the TFTR magnetic field coils. The computer system provides control of MG speed and power in a manual mode and an automatic clock-controlled windup mode.Given existing conditions of motor power and excitation, the automatic mode calculates the time required to accelerate from the present MG speed to the speed required at the start of the next TFlX pulse.Commands are then issued to the MG sets to accelerate at the proper time in the TFTR clock cycle in order that they reach the desired speed at the desired time.Monitor and control of MG circuits is interfaced with the computer control system through CAMAC modules. The paper details the control loops for the manual and automatic modes of the MG computer control system.The electrical power load required for a TFI'R shot can be as high as 950 MVA. To meet this requirement, two motor generator sets equipped with 600-ton flywheels store electrical energy in the form of rotational energy through the motion of the flywheels. During a shot, current is drawn from the stator winding of the generators to supply power to the coils.Presently, an motor generator operator controls the motor stator power reference and the frequency reference (sometimes called "upper speed limit") by a local hardwired control panel. From the TFTR control room, the Chief Operations Engineer (COE) instructs the operator on the proper settings for TFTR experiments. The computer control system will give the COE remote control over the MG speed and power in a manual mode and a clock-controlled windup mode. The manual metkessentially mimics the existing local control, except that the potentiometer adjustments from the local control panel are replaced by data entries into the computer control system. Clock-controlled windup mode will further automate speed control during a TFTR shot cycle. In this mode, the control system calculates the time required to accelerate from the present MG speed to the speed required at the start of the next TFTR pulse. Based on this predicted time, the system automatically commands the MG sets to accelerate at the proper time in the clock countdown in order that the generators reach the required starting speed by the start of pulse. This automatic wind-up mode makes it possible to keep the MG sets at low speeds for as long as possible. Current Mode of OoerationExperience has shown that for plasma shots requiring a Toroidal Field (TF) current of up to 50 kA, a MG starting speed of 80 Hz is required. The MG operator sets the upper speed limit at 80 Hz with a power reference of 7.5 MW. As energy is drawn from the sets, the speed drops below 64 Hz. The speed then begins to rise again to the speed limit ( fig. 1). It takes about 5 minutes for the motor to bring the flywheel back up to speed to be ready for the next shot. The operator will leave the speed at this elevated level unless the COE notifies him of a delay, in which case the speed and power refe...