The hermetically sealed refrigerant compressors have morphed away from mechanically switched (capacitive start) single phase designs.
Gradually, solid state, time-delay relays switched out the starter coils. This scheme would eliminate 'sparks.' However, the very nature of solid state switching dynamics causes 'harmonic skew' as the hyper-speed of the switching causes AC wave energy to 'kick back.' This tick is the rationale for SNUBBING resistors. The cheesy price pressures of the market must have had the early designs lacking any such 'wave quality' protection. (no snubbers)
Such a wave kick-back would be certain to trip a GFI at the lower thresholds. ( the common GFI on the shelf ) You'd have to install the (expensive, low demand) GFI which is tuned to let this distortion pass by without tripping. ( seven to ten times as insensitive, IIRC )
The LATEST (European) designs have morphed over to VFD. This scheme is largely government mandated -- to save energy. ( The manufacturers induced their European government (Brussels) to compel themselves to do what they wanted to do... bring out a new generation -- at a new standard -- that is not manufactured outside Europe.) (Well, at least for a while)
Like all VFD schemes, the line side current is rectified into a 'tank' of DC -- with a sweet buffer of capacitors... the 'tank.'
Then the DC is chopped into a synthetic THREE phase AC to drive the load side motor. This transformation is now so efficient that the design runs at lower power -- and with a virtually unlimited life. (until it leaks, or the SS drive fries)
This (pricy) scheme makes (economic) sense where juice is very pricy -- or politicized. (European 'Greens' are all about such tech)
One should expect to see this scheme enter the commercial refrigeration market in North America -- and then Congress will follow the Europeans and mandate it.
In some jurisdictions, the government even cross subsidizes their purchase. (the various Poco utilities issue a purchase rebate funded by the general rate paying electrical consumers -- very much in the style of the PV rebate programs we've all learned to love.
Of course, VFDs are notorious for dumping high-harmonics back onto the neutral/ return conductor.
All of which means that one can't really be certain if ones scope is reading actual sparking from a classic mechanical cut-out relay inside the hermetically sealed compressor -- or if it's bad wiring -- or if it's solid state 'recoil energies.'
It'd be nice if these machines were labeled -- and had a diagnostic jack that could be tapped -- just like those in modern automobile production. They are already being controlled by solid state chips. This would increase their manufactured cost by 0.01 % of the retail price.
This is all a part of the "Internet of Things" -- where all electrical power devices will become addressable -- which is already being proto-typed/ demonstrated.
Last edited by Tesla; 02/17/15 08:19 PM.
