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RESISTANCE BOXES
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The Resistance Boxes
are used for heavy duty requirements of controlling
the current in the circuit for various applications.
Starting and speed control of AC Slip Ring motors with Resistors is a universal method. The resistor is used to limit the inrush current and control the torque and speed characteristics of an AC Slip Ring Motor.
By changing the resistance in the Rotor Circuit in various steps (thru a Contactor), the starting torque and speed of the motor can be controlled to the desired value. |
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| APPLICATIONS : |
| • EOT CRANES & WINCHES |
| • RUBBER MILLS & FLOOR MILLS |
| • COAL MINES & SUGAR MILLS |
| • STEEL PLANTS & CEMENT PLANTS |
| • POWER PLANTS & PAPER PLANTS |
STANDARDS :
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| • BS 587 - 2 Mimutes / 5 Minutes /
10 Minutes / Continuous duty |
| • IS 12063 - for degree of protection |
| • NEMA |
| Normally Resistance Boxes are made by stacking resistance grids in an enclosure in following Types : |
| • Punched Grids |
| • Formed Grids |
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| RESISTANCE BOXES WITH PUNCHED SS GRIDS : |
Punched SS Grid Resistance Boxes consist of grids punched out of cold rolled sheets of corrosion resistant stainless steel sheets of grade AISI 304. The grids are rigidly mounted on four tie rods and insulated by interlocking porcelain bushes, also acting as intergrid spacers.
The punched SS grids are rigid and strong as the inherent strength of SS is very high and owing to its pressed and reinforced construction, they are unbreakable and can withstand heavy vibrations. Because of high surface area, the heat dissipation is very good and they can carry heavy currents. The intergrid connection is through bolted arrangement, to provide a reliable contact and eliminates any stress on the rods and insulators.
Number of tier assemblies are stacked one atop other to give desired rating.
Range :
Available in wide range from 8 Amp to 200 Amp.
continuous duty. Higher current ratings are achieved by parallel path combinations.
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RESISTANCE BOXES WITH FORMED SS GRIDS :
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The resistance element consists of stainless steel strip or wire of uniform section in the form of a wave profile having required number of loops to form a typical grid. These grids are then mounted on steel tie rods, insulated by micanite tubes and intergrid isolation is provided by mica washers, and the intergrid connection is through plated steel washers by pressure contact.
The main advantage of SS formed grid Resistance Box is that they are light weight, unbreakable, rustless and have relatively lower cost.
Range : The current rating normally ranges from 5 Amp. to
60 Amp. continuous. Higher ratings are achieved by
using multiple parallel paths. |
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