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• Checking mV drop with an accurate meter which indicates when shorted • Twist the connecting leads while measuring to avoid false pick ups • Measure current with clip on meter • The values of drop measured should be less than 4.0mV at the rated current of contactor for AC3 duty. mV volt drop can be calculated by given formula: Milivolt drop test Corrective action: If milivolt drop is more, then it is indication of bad joints For case A & B) Clean the surfaces, apply Dowells crimping compound & re-crimp cables Image A Image b For case C) Higher value of mV drop in this case could be due to either case A or B; In case of persistent higher value, replacement of the entire contactor is necessary Image C ........

This circuit is a DC voltage output from a small DC input generate large voltage.It ‘s easy and quick to do, and reducing the value of the Z-diode, the circuit can be universally adapted to other output devices of the circuit voltages. The give and all diagrams represent a DC converter with 12V battery 9 volt DC input and output.     12-9 Volt DC to DC Converter Circuit Diagram With the 10V zener diode, as in the diagram, the output voltage is approximately 9.3 volts DC. The supply voltage is used, should always be at least a few volts higher than the Zener voltage. In this example, I have a 12 Volt DC battery to provide regulated 9-volt DC output.

There is little to be said about this circuit. All the work is done by the regulator . The 7809 can deliver up to 2 amps continuous output whilst maintaining a low noise and very well regulated supply. The circuit will work without the extra components, but for reverse polarity protection a 1N5400 diode (D1) is provided at the input, extra smoothing being provided by C1. The output stage includes C2 for extra filtering, if powering a logic circuit than a 100nF (C3) capacitor is also desirable to remove any high frequency switching noise. Circuit diagram: Parts: C1 = 100uF-25V electrolytic capacitor, at least 25V voltage rating C2 = 10uF-25V electrolytic capacitor, at least 6-16V voltage rating C3 = 100nF-63V ceramic or polyester capacitor IC = 7809 Positive Voltage Regulator IC D1 = 1N5400 Diode