Page 220 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

A step down transformer X3 is used to keep cut off relay is energised condition when the mains AC supply is cut
off to the charger circuit. Relay RL1 used to cut off the AC mains supply to the charger circuit. Pole P1of relay RL1
is connected to AC mains supply and pole P2 is connected to cut off circuit.
Relay is energised by the centre tapping of potentiometer, which is set such that, the current in the charger circuit
exceeds then it is energised and poles P1& P2 are connected to normally opened (NO)pin, switching ‘Off’ A/C
mains supply to the circuit.

The test switch S3 is connected to check battery polarity, reset switch S4 is used to reset the charger, when any
fault occurs. Then the charger is cut off and the Switch ‘S1’ is mains on/off switch.
A fully charged lead acid battery must be 2.1 volt/cell during on charge. It will increase upto 2.7V/cell. The voltage
of a battery is multiple of the number of cells.
In discharged condition the voltage is 1.8V/cell, it should not be further discharged in this condition as it may
permanently damage the cell.
E.g A 100AH (ampere hour)battery requires (100 AH/10Hr=10 Amp) 10 Amp. Charging current for 10 hours for
fully charged. To get complete discharge at the rate of 5Amps will require 20 Hrs.

The fully discharged battery requires about 11/2 times more to get charged .If the battery is in dead (or )not in use
for long time even in normal changing current is passed. These dead batteries require higher charge voltage to
start the charging current.

Checking of battery : Acid level and specific gravity of electrolyte, will indicate the condition of battery whether
it requires charging or not.
The hydro meter is used for checking the acid level in a battery .The scale in marked in the hydrometer from 1100
to 1300.when it is inserted in the battery, the reading
i 1100-1150 -indicates battery is down
ii 1200-1250- indicates battery is o.k.
iii 1250-1300 indicates excess acid

Voltage testing : By using high rate discharge tester, the voltage the each cell must be 2.1V, If it indicates below
than 1.8V, then it shows the battery is in fully discharged. It is still below 1.8V.Then the battery becomes dead
condition.
Inverter : It is an electronic device, which converts a D.C potential (voltages) normally derived from a lead-acid
battery into a stepped-up AC potential (voltage) which is similar to the domestic AC voltage.

Locating the fault and troubleshooting of an inverters which provide sine wave outputs or the use of PWM(Pulse
Width Modulation) technology is very difficult. (Fig 2)

Fig 2

Switching circuits : It is the input stage of a inverter. This circuits supplying the power to further stages and
connected to battery. The DC supply of battery in this supplies to the switching circuits for various needs.

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CITS : Power - Electrician & Wireman - Lesson 93-100 CITS : Power - Electrician & Wireman - Lesson 93-100