DESCRIPTION
At the start of the cool-down step, the DTC checks the current temperature setpoint, the
paddle setpoint (target temperature) and the ramp (slope) to see if forced cooling is
necessary. If it is, the DTC calculates a profile (temperature over time) required to reach the
target setpoint, and sets the blower speed to an appropriate value (determined by an
algorithm). While cooling is in progress, the DTC applies power to the element end zone to
maintain an even cooling “ramp” and to maintain a flat zone.
When the system reaches the paddle setpoint, the blower is ramped down and turned off. At
this point the DTC switches automatically back to cascade control.
2.7 Heating elements (disposacore)
•
The furnace contains 3 or 5 zone heating elements of the standard Tempress
Systems specification and are used for optimum temperature characteristics.
•
The furnace can contain any of the following heating elements: a multipurpose
Kanthal A-1 coil, a high temp APM coil, an ultra high temp Kanthal Superthal
®
coil,
Low temp white John, MRL heating elements or light Gauge for high/low
temperature applications. Insulation made from high purity, high density, vacuum
molded alumina silica fiber
(optional light Gauge). It depends on the process
temperature, which kind of element is used. Custom desired other elements can be
implemented on request.
•
Over temperature protection is provided by an Excess Temperature Controller,
connected to separate Thermocouples. See section
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found.
•
Each heating element has its own transformer with isolated coils powering individual
control zones via high-efficiency zero-crossover fired Silicon Control Rectifier (SCR)
power control modules.
•
One tube switch per heating element, to shut off one tube only.
•
Tube sizes depending on customer demand.
•
The combination of the special coil-design, insulation, stainless steel shell and the
DTC guarantees:
•
better uniformity
•
long lifetime
•
energy saving
•
no element sagging
2.7.1
Tube heating module
This module, most of the times multi-zone, consists of a Fibrothal
®
heating element with
embedded Kanthal alloys and a stainless steel mantle. This module is meant for diffusion
furnaces. See Figure 2-5.
The advantages of this construction are:
•
High temperature equability
•
Exact temperature profile
F
URNACE
R
EFERENCE
M
ANUAL
2-7