"We hired an electrician to hook up the travel trailer to my mother in laws electrical box. Everything was working fine before leaving town"
Do you mean everything was working fine AFTER the electrician wired the box, or working fine only BEFORE the wiring was done. If it smoked AFTER the wire job was done, 100% guarantee the job was done wrong, ie wired for 220 volts. Electricians unfamiliar with 30 amp 120 volt RV plugs do this all the time because the plug looks similar to a 220 volt plug and they've never done any RV work.
