Cable preheater

The operating principle for CLIP-H cable preheater is based on the device’s ability to deliver a constant amount of thermal energy to the conductor regardless of line speed.
Power transfer occurs by “conduction,” that is, the metal wire is traversed, in the heating section, by electric current by electromagnetic induction supplied by a special transformer, in which the secondary winding is represented by the loop(s) of the conductor itself.

The transformer is powered on the primary winding by an industrial frequency and variable voltage static converter, J-DRIVE series, equipped with fine and precise control of output current and voltage.

Since the wire does not perform mechanical work the energy provided is translated into heat by the Joule effect and results in its heating.
Thermal dissipation occurs on the surface of the conductor, and since these are low-temperature heats, the existence of linearity and proportionality between power dissipation and temperature can be assumed, supported by the following expression:

From electrical engineering, Ohm’s law takes us back to the equality between the Amount of Energy in Joules/sec and Power expressed in Watts, and wanting to estimate the Power to be transmitted to a conductor of cylindrical shape and known resistance, we must refer to the fundamental law expressed by Watt = V * I and best represented by the better known expression:

which recalling the formula defining electrical resistance as R = ρ* ℓ /S , results simplified to Watt = k ^V2, a formula that clearly shows that, for a given length and cross section of wire, Power results proportional to the square of the applied voltage.

It follows that, the transfer of an amount of energy in Joules/sec (Watts) to a conductor moving at variable speed, with fixed length (distance between pulleys) and known resistance, changes the previous expression to m/sec = k ^V2 from which originates the following law that expresses, in quadratic form, the value of the Preheater Output Voltage as a function of line speed.

The generation of this law is easily implemented through the use of a PLC programmable controller that, through color HMI interface, allows the plotting of programmable curve families for each conductor type and material type, starting from a stored basic quadratic curve.

A signal is finally sent from PLC to the static device J-DRIVE, which accurately delivers the required heating power.

A further consideration should be reported by resuming the initial power formula Watt = ^V2/R where, substituting for R the corresponding representation showing resistivity coefficient, length and cross section of the wire R = ρ* ℓ /S where:
ρ = Resistivity of the material (rho)
ℓ = Conductor length
S = Section of the conductor (^S=πr2)

it can be seen that the heating power being directly proportional to the cross-section it will be sufficient, for the same type of wire, to simply shift the programmed heating curve, up or down, without the slightest intervention in the stored curve profile.