Various embodiments provide an apparatus and method for collecting and distributing power usage data from Rack Power Distribution Units using a wireless sensor network. The control system determines the actual coefficients of export flow for the compressors, compares the actual coefficients of export flow with a common or individual coefficients of export flow setpoints generated by one or more central controllers, and then generates control signals for adjusting the operating points of the compressors in order to load balance the compressors. The browser then creates JavaScript objects that can be called directly from other JavaScript code on the client side, and which communicate with the server-side method. The second layer is made of fine-grained graphite and is glued to the first layer. The protecting cover is for shielding the driving circuit module to prevent the driving circuit module from being irradiated by a laser beam in the laser releasing process.