I am designing a circuit to drive a DC motor from rectified mains voltage. For that, I have added a 1200uF capacitor. My problem is that this circuit is supposed to work on a user's home power plug, and the capacitor charging curve when I first turn on the circuit has a current peak high and slow enough to trip a 16 A breaker. How would I go about designing this so the circuit can work on a normal home breaker?
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5\$\begingroup\$ Why do you need a capacitor? Think hard about that. \$\endgroup\$– Andy akaCommented Jan 7, 2022 at 15:19
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1\$\begingroup\$ what are the other constraints? A series resistor to control a precharge, shorted by a resistor is good, but delays startup. A PTC thermistor in series will reduce the surge. For a large load on the supply, diode-capacitor is frowned on these days, you should use a proper power factor corrected supply, which will have its own soft start included. \$\endgroup\$– Neil_UKCommented Jan 7, 2022 at 15:23
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\$\begingroup\$ Are you rectifying 120 240 or 208? No bulk cap required!, just for RF, use metal film across motor \$\endgroup\$– D.A.S.Commented Jan 7, 2022 at 17:56
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If anyone else has the same question as I had,the solution I found for this specific case is using a negative thermal coefficient (NTC) thermistor in series with the rectifier. At room temperature it has some resistance (10 ohms in my case) and reduces the current inrush, but as you pass current through it, it heats up and its resistance decreases, so in steady state it works as a short.