Asprie R15 slows down when plugged in

DBocce

We have an ACER Aspire R5-571T laptop running Windows 10.  When the laptop is plugged in, it charges fine but the processor speed drops to 0.4 - 0.5 GHz.  When not plugged in, the processor increases to the 3.0 GHz range (on high performance); we get similar behavior under the balanced power option as well.  You can clearly see the difference in gaming videos (very 'laggy' when plugged in; works perfect when unplugged) and the response of the system (very slow plugged in; fine when unplugged).  I do not believe it's the adapter (we have two of these laptops and both chargers cause the same problem).  I've seen other posts about this issue occurring with ACER machines, but no solutions.  Any help would be appreciated.

Thanks. 

JackE

Uninstall, don't just disable, any non-Microsoft virus scanners. Also uncheck fast startup box in Control Panel power button changes to disable fast boot. Shut down. Restart. Then battery must be near 100% charge, charger plugged in, and power plan all set to  performance mode BEFORE trying heavy gaming loads. Jack E/NJ