Verimark Genesis Cyclovac

I bought the Genesis cyclovac last year June, it has been cting ever since I bought it. It works for 15min max then turns off automatically. After 30min or so it switches back on again. The motor started sounding funny so I got it changed last month, I got the vacuum back last week and started using it today, cleaned the filters and but it still switches off every 5-10min. How are we expected to finishing our work with a vacuum that won't operate for 10min?