The environmental chamber is now in the SEARC lab at St. Lawrence College – see last week’s post from fellow researcher Michael Clarke. The next challenge for the IITF team is to design a data acquisition system that complies with the physical and ergonomic constraints of operation inside a closed power supply and data acquisition cabinet and conforms to industry safety standards.

The sensor board must be able to support the weight of all the sensors and equipment and be mounted inside a cabinet approved by the Electrical Safety Authority (ESA). The cabinet design must allow for wiring and the sensors kept accessible.

A 19 x 24 inch shelf sits inside the cabinet with all of the required equipment installed onto it. The research team agreed that making a shelf to attach to the vertical beams within the cabinet would provide a sufficiently sturdy surface to mount to and have plenty of space above and below for running wires neatly.

Inverter Design

 

The voltage sensors (G) were placed in the corner near the front panel of the cabinet to isolate high voltage signals and prevent electrocution should someone stick a finger through one of the holes in the back panel of the cabinet. The terminal blocks and 24v supply (F) are located towards the centre of the board to allow easy and accessable wiring to power all of the sensors. The chassis ground screw (E) is located near the 120VAC terminal blocks as well as the emergency stop contactor (C) to provide a common grounding connection through the entire cabinet. The contactor is positioned below the 3 phase AC input for the 30kW power supply that will be mounted inside the cabinet. This will minimize the wiring distance from the contactor to the power supply, and allow for the attachment of a tap to one of the 3 phase lines to provide 120v power to the Data Acquisition (DAQ) unit(A) and our 24v power supply (F). The current sensors (D) are aligned near the centre of the board linearly because the wires from the output of the inverters to be tested need to run into the cabinet, through a current sensor, out of the cabinet, and then connect back to the power grid. With the current sensors aligned this way, the wires can be fed into the cabinet through one of the holes in the back panel, underneath the board, and then loop around through the sensors and pass through the back panel again. The wire for the temperature and humidity sensor (B) can run underneath the sensor board to connect to the box.

The shelf was constructed out of 1/16 inch aluminum sheet, with ¾ inch aluminum angle for support, and angle braces to mount it to the cabinet. All of the sensors are mounted onto DIN rails along with the 24v power supply and the terminal blocks. All other components are bolted directly to the aluminum sheet. Once the front and back panels for the cabinet are completed, work will begin on wiring up all of the signal wires to the sensors, as well as running power to the environmental chamber and to the cabinet.

By Keegan Heffernan, Student Research Assistant, IITF team, SEARC

Designing the Inverter Sensor Board
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