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Xringer · 09-02-16, 12:23 PM

It's right around 246 vac today. It's a beautiful Fall day in NE.. No AC needed.

Of course the new Gree wants 208 to 230vac..

(see pic)..

The AC to DC part of a M/S unit, is a simple Unregulated DC Power Supply.
A higher AC voltage into a rectifier bridge gives a DC voltage that is dependent on the peak voltage of the AC grid, and power that
(high-current capable) DC voltage delivers to motor loads etc can not be controlled by lowering the DC voltage,(not economically) but only the timing of the pulses.

So, those extra high voltage pulses are going to be hammering the M/S compressor motor..
That means the controller has to be smart enough to shorten the pulse width, when the line voltage is causing extra high DC voltage into the motor controller's switching devices..

Sounds like high speed decisions have to be made, if the voltage suddenly goes up or down (from the norm)..

I'm thinking back to the snowy day when my Den Sanyo main board got zapped..
The grid fail was so short, it was hardly noticed. My PC display went black.
The PC kept on running.. The stove clock displayed 'PF', all the cable boxes on the street re-booted..
But, the den Sanyo noticed.. In a major way..
Perhaps it attempted to compensate for the drop, and stretched the next pulse a Bridge too Far..
Flooding the switching devices and the bootstrap parts, with way too much power.?.(in the form of higher voltage).
I think the defrost cycle was running, and power use was around 2KW? when the PF hit..
I know any surge (4+ KW?) was too short to register on the TED.
At least it died a quick death.. It was only I that lingered, wondering.

09-02-16, 12:23 PM	#31
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	It's right around 246 vac today. It's a beautiful Fall day in NE.. No AC needed. Of course the new Gree wants 208 to 230vac.. (see pic).. The AC to DC part of a M/S unit, is a simple Unregulated DC Power Supply. A higher AC voltage into a rectifier bridge gives a DC voltage that is dependent on the peak voltage of the AC grid, and power that (high-current capable) DC voltage delivers to motor loads etc can not be controlled by lowering the DC voltage,(not economically) but only the timing of the pulses. So, those extra high voltage pulses are going to be hammering the M/S compressor motor.. That means the controller has to be smart enough to shorten the pulse width, when the line voltage is causing extra high DC voltage into the motor controller's switching devices.. Sounds like high speed decisions have to be made, if the voltage suddenly goes up or down (from the norm).. I'm thinking back to the snowy day when my Den Sanyo main board got zapped.. The grid fail was so short, it was hardly noticed. My PC display went black. The PC kept on running.. The stove clock displayed 'PF', all the cable boxes on the street re-booted.. But, the den Sanyo noticed.. In a major way.. Perhaps it attempted to compensate for the drop, and stretched the next pulse a Bridge too Far.. Flooding the switching devices and the bootstrap parts, with way too much power.?.(in the form of higher voltage). I think the defrost cycle was running, and power use was around 2KW? when the PF hit.. I know any surge (4+ KW?) was too short to register on the TED. At least it died a quick death.. It was only I that lingered, wondering. Attached Images __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..