DIY 230vac adjustable power limiter

Xringer · 03-21-11, 04:14 PM

This 230vac adjustable power limiter can be pre-set to turn off AC power
to a load and reset itself within a few hundred milliseconds.

The blue device on the left, is a non-contact current sensor.
It's set-point has been set to about 9.5 amps. (~2300 watts).

The dark blue box (lower right) contains a transistor switch that sends
5 VDC to the two SSR on each side of the (open) 10A breaker in the middle.
(The green LEDs on the SSRs indicate they are on).

If the load exceeds 2.3kw, the current sensor closes it's contacts.
This grounds out the base of the transistor, shutting it off.
That removes the +5v control signal from the SSRs, shutting them down.
(The SSRs turn off as the AC voltage crosses Zero volts).

~~~ The Sanyo hiccups!

Once the current stops, the current sensor shuts down.
(It gets it's power from the magnetic field of the 230vac line).
It's contacts become open. A cap on the base of the transistor
charges up and the transistor turns back on.
That turns on the SSRs and the Sanyo restarts within a few seconds.
(The SSRs turn ON as the AC voltage crosses Zero volts).

03-21-11, 04:14 PM	#1
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	DIY 230vac adjustable power limiter This 230vac adjustable power limiter can be pre-set to turn off AC power to a load and reset itself within a few hundred milliseconds. The blue device on the left, is a non-contact current sensor. It's set-point has been set to about 9.5 amps. (~2300 watts). The dark blue box (lower right) contains a transistor switch that sends 5 VDC to the two SSR on each side of the (open) 10A breaker in the middle. (The green LEDs on the SSRs indicate they are on). If the load exceeds 2.3kw, the current sensor closes it's contacts. This grounds out the base of the transistor, shutting it off. That removes the +5v control signal from the SSRs, shutting them down. (The SSRs turn off as the AC voltage crosses Zero volts). ~~~ The Sanyo hiccups! Once the current stops, the current sensor shuts down. (It gets it's power from the magnetic field of the 230vac line). It's contacts become open. A cap on the base of the transistor charges up and the transistor turns back on. That turns on the SSRs and the Sanyo restarts within a few seconds. (The SSRs turn ON as the AC voltage crosses Zero volts).