LIQUID RESISTANCE STARTER TESTING OF SODA WATER

THUMB RULE

1 LITRE WATER CONTAINS 10 gm SODA.

Method to test resistance of the soda water.

Soda is basically mixed with water to lower the resistance of water. Now the method to check the resistance of soda water is as follows,

 Let the rotor voltage is 1600V.

Now, the resistance needed is 2.4Ω(say)

We know, I=KV/R,

Therefore, I=5 amp.

Take 12V from secondary of a transformer, connect one terminal with the star connected moving electrode, the other terminal with one terminal of the fixed electrode. An ammeter is connected according to the fig above. As we go on adding soda, check the reading of the ammeter. When the reading shows 5 amp, it will mean that the resistance has reached 2.4 ohm.

The fixed and moving electrode must be shorted within 30 sec.

CALCULATION TO DETERMINE TYPE OF CARBON BRUSHES

CALCULATION TO DETERMINE TYPE OF CARBON BRUSHES

Passing of current between brush and slip ring is called electrical greasing.

Types of Brushes

Group	% Cu	Current Density(A/cm2)
1(metal graphite )	85	20
2(metal graphite )	75	17
3(metal graphite )	65	12
4(electro graphite )	0	8

DIMENSIONS OF DIFFERENT BRUSHES

TR ₅ – 38X32X22

NGEF-1> 315R-40X40X20

           2>280-40X32X16

TR₄ – 38X32X16

Let us take example of NGEF 315R GROUP 3.

Area touching the slip ring- 40x20=8cm²           

Capacity of a brush= 12x8=96A

Let us take a motor whose secondary current is 260A

 2 brushes needed, so capacity of one brush will be 130A

So 3 Group brush will not work, we take Group 2 brush.

For group 2, capacity of each brush will be 17x8=136A

We can use this brush.

Therefore, to order a brush we will tell the vendor specifications as follows:

NGEF 315R brush, Group 2.

Calculation of Spring Tension of Brush

Range available- 180-200 gm/cm²

                               200-220 gm/cm²

For NGEF 315R Group3, area=8cm²

Let’s take 200 range.

So, tension will be 200x8= 1.6KG

Coefficient of Friction

 

                                                           12 A, 120°C

At the point 12 A coefficient of friction is 0.1 which is lowest, here heat developed will be minimum, so an increase or decrease in temperature will result in an increase in coefficient of friction, which  is undesirable.

Electric motor control damper actuator

Electric motor control damper actuator – it has 3 phase induction motor its operate the lever this actuator has primary and secondary gear secondary gear also known as worm gear at front side there is indicator which shows the position of damper at the back side wheel and handle is given if we want to operate the actuator manually then push the handle clockwise this thing bypasses the motor now we can easily set the position of damper as per requirement through the wheel in this actuator there is an advantage that we can adjust the damper at 30% , 40% etc but in most pneumatic actuator(with single solenoid coil) we operates only either fully open or fully close condition

Electric motor damper actuator has 6 limit switch as described further

2 limit switch for full open (1 for retendency in case failure)

2 limit switch for full close condition (1 for retendency in case failure)

1 for open torque (when we open the damper for flow if there is obstruction like material jamming or some material struck around)

1 for close torque (when we close  the damper if there is obstruction like material jamming or some material struck around foreign material coming