Simple retrofitting of power stack controllers

Paul Boughton

Sprint Electric presents an external thyristor stack controller called the PLXD. Thyristor stack controllers are ideal for controlling DC 6 pulse or 12 pulse, 2 Quadrant or 4 Quadrant thyristor power stacks. A thyristor stack controller is used together with an external thyristor power stack when a modular drive is not capable of delivering enough power. The external power stack can be designed to control motors up to many thousands of Amps and is controlled very simply by the same PLXD unit. Thyristor stack controllers are used in a wide range of industries where high power electric DC motors are involved, for example in hot rolling mills, plastic extruders, rubber mixers and many more.

The main advantages of the PLXD thyristor stack controllers are that they can be designed into a new installation, or easily retrofitted to an existing thyristor power stack where the control electronics need updating or require adding into a field bus topography network. The PLXD can be supplied with all the latest field bus protocols including Profibus, Modbus RTU, Modbus TCP/IP, CanOpen, Devicenet, Ethernet and more. The same unit is used for 2 Quadrant and 4 Quadrant power stacks. 6 Pulse and 12 Pulse can also be accommodated.

PLXD thyristor stack possess all the functionality of Sprint Electric’s known PLX DC drives range. The PLXD provides gate drive pulses for driving user supplied pulse transformers with primary pulse current up to 1.5 Amp. There are terminals to accept an externally generated isolated armature current signal, field signal, thermal heatsink sensor switch, and high voltage armature voltage feedback. The unit also provides a +24 V supply for the gate drive pulse transformers that is short circuit protected.

The following stack configurations can be driven by the PLXD: 6 pulse 2 Quadrant bridge (6 thyristors), or 2 bridges in parallel (12 thyristors), as well as 6 pulse 4 Quadrant regenerative anti-parallel bridge (12 thyristors). Extra stacks can be used in parallel within the gate drive capability. All customer control terminals are the plug-in screw terminal variety. The PLXD can be used with up to 690 V AC on its 3 phase auxiliary supply inputs (EL1/2/3). The external stacks can be of higher voltages if required. The armature voltage inputs can monitor up to +/-1000 V DC. There is an integral motor field bridge with independent single phase AC supply inputs (EF2/3) for controlling fields up to 32 Amps. The internal field bridge supply input voltage rating is 480 V AC. Provision is made for providing an external field feedback signal and controlling an external field with user supplied primary gate pulse transformer drivers.