An Integrated Induction Power Supply Controller

The introduction of high-power semiconductors opened the door to the use of solid-state technology in induction power supplies. This resulted in more efficient power supplies in the medium- to high-frequency range. As a result, furnace sizes were reduced and power density and production rates increased. In conjunction with the power electronics, specialized control systems were designed to automatically regulate power without the need for changing capacitor steps. The original controls were based on frequency modulation and were not robust enough to respond to rapid changes in the melting process.

The Z control introduced in 1989 used phase-angle modulation with a more sophisticated control scheme. Z control systems were more robust than their predecessors. They could adapt quickly to rapid changes in furnace load and featured much better power semiconductor protection schemes resulting in more reliable equipment operation.

In pursuit of an even more reliable controller, the EZ (Enhanced Z) control system was introduced in 2004 as a replacement for the Z control. The EZ controller offered enhanced detection of abnormal events, improved immunity to electrical noise and better power electronics protection schemes than Z control systems resulting in further enhancement of equipment reliability. Both the Z and EZ controllers provided a connection point for a Data Acquisition Interface board which offered visual diagnostics and digital connection to customer controllers.

The ever increasing industry demand for enhanced diagnostics, predictive maintenance and the emergence of Industrial IoT and Industry 4.0 data-sharing networking functions mandated a new control system. The I-EZ control board was developed to encompass all these requirements and provide a flexible platform for remote diagnostics, troubleshooting, and remote data access. (See Figure 1.)

The I-EZ control board integrates the EZ controls and the Data Acquisition Interface circuitry and functions onto a single control board. The analog power supply signals are digitized using high speed analog to digital converters and then processed using a Digital Signal processor (DSP) to make the board truly a digital controller. The board also has a built-in 24 channel “oscilloscope” which continuously measures and records data. Data from the “oscilloscope” can be remotely accessed or sent to Inductotherm for remote troubleshooting. (See Figure 2.)

In addition, the I-EZ controller can store up to 32 different board configurations. This allows a single spare controller board to be used for multiple power supplies.

Noise immune fiber-optic cables are used to transmit firing pulses from the I-EZ controller to the power electronic firing modules. The built-in LCD display provides advanced diagnostics for easy troubleshooting. The on-board SD card, the two USB ports and an Ethernet connector allow for data storage and remote connectivity, respectively.

There is also a web server, a local WIFI and a Bluetooth module on the I-EZ controller to provide IoT capabilities.
Robert Keshecki is Director of International Sales at Inductotherm Corp. Contact him at [email protected], or visit www.inductotherm.com