Annoying PWM sound from Xantrex inverter

Gerald55 wrote:
I finished setting it up after sundown and did my initial testing in the dark. The next day, sun shining on entering my rig, I could hear an annoying buzzing sound coming form the inverter. The inverter is completely off at this point.

Do you mean it's in standby so it's not off?

A bunch of testing seems to indicate that the sound occurs when my PWM solar controller (Samlex 30A) goes into current limiting mode (i.e,. absorption aka CV stage) the noise starts. The controller uses PWM at this stage and it seems that the fluctuating voltage/current causes some kind of resonance in the inverter.

FYI Pulsed type of power has a large number and frequency of power transients and can cause various symptoms, especially the way yours is wired.

Any ideas to get rid of the noise? Do MPPT controllers have PWM-like/switching behavior when they are limiting current?

Yes

Rewiring the controller AND the house wiring directly to the battery may/may not solve the problem. You may have incompatible equipment which sometimes becomes a learning opportunity for a DIY project.

There is normally absolutely nothing wrong with wiring a solar controller directly to the inverter depending with adequate wiring. It helps to have a controller with battery voltage sense capability however. My MPPT controller is wired to the inverter terminals and works great with no noise but with different equipment.