RC linear slider rheostats consist of one or more cylindrical porcelain tubes with an alloy wire resistive winding and by one or more sliding contacts on the winding along the lines of the cylinder, moved by a knob or a worm screw.
These rheostats are simple, sturdy and easy to use and install.
They can be used for an infinite number of applications, especially in laboratories, whenever there is a need for adjustment of voltage or current.
Vast experience has enabled the most opportune choices in terms of the materials used: the cylindrical tube in special porcelain has high mechanical resistance and thermal shock resistance; the resistive alloy used is generally constantan, which has a negligible temperature coefficient; the support plates and perforated protective sheets are fired after painting in a high temperature kiln and thus ensure the colour is long-lasting and unchanged over time.
RC2 and RC3 can be supplied respectively with six or nine output terminals.
Rheostats with graduated windings:
when the “adjustment ratio”, namely the ratio between the rheostat excluded and with the rheostat completely inserted, is high, or the law of variation of the resistance must have a particular trend, the winding is divided into several sections, created with wires in various diameters. When ordering, simply indicate, in addition to the overall resistance, the initial and final current, or send a graph showing the resistance values in several points of the rheostat.
Screw adjustment:
if required, instead of direct manual control, the brushes can be controlled by a close-thread screw (10 mm).
This method is necessary if the rheostat is mounted in a position behind the control panel, or the motorised control.
Rheostat with zero excluded:
if the user circuit has to be open in the starting position of the stroke of the contact, two collar terminals can be open, one of which is connected to the winding, to create the “zero interrupted” or “excluded” condition.
Use with ventilation:
RC slider rheostats are most frequently used with inert load to test generating machines or measurement instruments. They are installed to ensure good ventilation. Since the ventilation reaches 2.5 m/sec, the rheostats can be overloaded even 100% and even more for brief periods.
Adjustable passive loads:
a load for example of 2 kW, 220 V, adjustable from 2 to 0.2 kW must be created, namely from 100% to 10%, with continuity. Two 48.3 Ohm RFC wire wound cemented resistors will be used, between them in parallel, capable of dissipating the planned 2 kW with modest ventilation.
In series RC2 will be installed, namely a RC with 2 parallel resistors with an ohm value 9 times greater than the RFC, namely about 435 Ohm, realised in 6 sections wound with decreasing diameter wires, in harmony with the decreasing current resulting from the increased, inserted resistance.
The choice of resistance values included between the minimums and maximums in the table refer to the normalised table E12.
Precision ± 10%.
Particular values available on request.
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Industrial resistors, for starting and braking motors, railway traction, grounding resistors, medium and high power resistive loads, toroidal rheostats and flush-mount potentiometers.
ItalOhm S.r.l. Via della Meccanica, 13 – 36100 Vicenza – ITALY Tel: 0039 0444 965 365 Fax: 0039 0444 965 366 e-mail: info@italohm.com
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