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# 140 to 280 volt ac stabilizer circuit diagram

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#### elanshul

##### Junior Member level 2
Dear all,
can anyone help me for 200-240 volt AC out stabilizer which can operate from minimum 140 volt input using 2 relay and without chattering the relay also transformer use his own LT i.e. no additional transformer for relay operation. please arrange for transformer taping relay connection and circuit diagram. i will be highly obliged.

Since you're transforming, you can multiply the voltage as required by varying the turns ratio. So what really needs to be mapped are the input to output voltage spans. Vin goes from 140 to 280 which is a span ratio of 2.0. Vout goes from 200 to 240 which is a span of 1.2. This can most easily be worked out with logarithms. Log10(280V/140V)=0.30103 for the input. Log10(240V/200V)=0.079181 for the output. Therefore the ratio of span widths is 0.30103/0.079181=3.8010784 spans of the input compared to spans of the outs. Because this is greater than 1, there is a need for a stabilizer to chop up the input range into multiple spans and map each of them into the same narrower output span using various turns ratios. So how many are needed? Well the next higher integer about 3.8010784 is 4, so 4 spans will be needed. This can be encoded using 2 binary bits, each of which switches taps to apply a different scale factor. The scale factors (transforming change ratio) implemented by each of the bits should differ by a factor of 2 because they are binary and we are talking about multiplicative factors here, not additive. Calculate this in the logarithmic (dB Gain) domain, and then map it back to the turns ratios.

In order to not chatter relays, you need to look at the input signal to decide which taps to use, not the transformed output which is getting switched. Since 3.8010784 is less the 4.0, you have a little extra span left over which can be used for hysteresis at the crossovers to prevent chattering.

schmitt trigger

### schmitt trigger

Points: 2
Here is a commercial solution which exactly matches your specification , it also has 7 segment LED display for input/output voltage display.

Jeff;
The log ratio approach....very clever, indeed.

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