Shorting of more than one turn through Carbon Brush.( Voltage per turn affect). In windings with thinner wires that have high resistance perturn - this heating is lower in comparison to large heating on thicker wires. In Dimmers of 2 Amps, -this heating is very low in comparison to 200 A coil

1. A
In Dimmer Dot Variable Voltage Transformers - TYPE GDCB, this INTER TURN
SHORTING CURRENT is BLOCKED by a Special winding Technique & Chokes - so
that Current is Collected from two turns by two separate & Isolated current
collectors & these two separate currents.

2. These Chokes / reverse biased diodes, block the transfer of current from one turn
of the winding to the other thus no shorting of turns takes place. Since the turns
do not get shorted, in these units, the carbon brushes are replaced by solid
copper / Copper Cadmium or other alloys - that again slide over the winding
producing virtually no heat on account of any of the above mentioned causes.
Breakage or wear & tear of Carbon issues are totally eliminated- thereby
introducing high degree of reliability in this very critical equipment used in all
applications requiring varying voltage or control of voltage. Thus the cause &
affect of heating at Current Collection points are virtually eliminated - making the
units to run cool, saving on Large JUNK of Carbon & Contact Losses, which in
conventional variable transformers dominated all other losses .There is
VIRTALLY95 % SAVING in these losses and the units run cool - making the Dimmer
Dots of even 200 A in Air Cooled Version.

3. Higher AIR COOLED capacities are being worked out are in pipeline. We have
28/60/100 & 200 A units ready for delivery. THE DESIGN is protected vide Patent
No 3095/Del/2011 (applied for). With the break through in technology in this line
- we are geared up to produce Variable Transformers upto 5000 A Capacity with
sliding copper contacts . This technology is considered farsuperior over Rollar
Carbonsetc .for Larger Capacity Variable Transformers.

4. Winding on following varying accounts.
1. Shorting of more than one turn through Carbon Brush.( Voltage per turn
affect). In windings with thinner wires that have high resistance perturn
- this heating is lower in comparison to large heating on thicker wires. In
Dimmers of 2 Amps, -this heating is very low in comparison to 200 A
coil .A carbon brush of High Resistance will limit this heating on No Load
in higher capacity say of 200 A Dimmers - but will get heated up
substantially on account of para 3 below.

5. 2. A carbon brush of LOW RESISTANCE will produce high INTER TURN HEAT
on Large capacity Dimmers say of 200 A units on NO LOAD but will
produce lesser heat on LOAD. To limit this heat- Dimmer manufacturers
work out various ways - like selection of grade of carbon, provision of
HEAT SINKS on the Brush Holders, providing heat sinks on the winding
etc. etc. - but by & large - this heat had been a challenge in the
manufacture, design & usage of these Dimmers.

6. 2. Contact resistance (Rc )
ofCarbon & varieswith Pressure on carbon brush,grade or Characteristics of the
Carbon Brush Material, etc. - Heat Generated=l2XRc Watts.
3. Current Conducting properties of carbon brush - l2R heating on the Carbon
X Section carrying current.

7. 4. Self heating of Winding Turn because of self shorting of Copper Turn - due
to length of carbon contact on winding - the heating circuit is formed along the
length of copper turn in contact with carbon. If length of Carbon to collect current
covers say 1/3 length of mean turn of copper as happens in say 200 A Dimmers,
the heating will be more if say 1/10 of the winding self shorts the copper length.
Longer the Carbon - more is heat & vice versa.
Thus - heat produced at Carbon brushes has been limiting factor & a serious issue
in use of variable transformers to the extent thatupto 28A approx.- Air Cooled
units could be marginally & safely produced in Single Coil & above this units
arerecommended to be used in Oil Cooled condition only - so that heat generated
at carbon brush pointsgets dissipated to largeOil content/and even radiators of
containers.