Technical_reference - 第16页
Technical Service Manual 16 Revision Dat e: August 2004 HEATING CELL DESCRIPT ION HEA TI NG CELL CROSS-SECTION CONSTRUCT ION: The heat Cells are assem bled and sealed as self -contained units with the Fan Motor, and O ve…
Technical Service Manual 15 Revision Date: August 2004
2- B) INTERLOCKS:
1. Over Temp Switch (es):
Bi-metallic snap switch (es) mounted on each Cell Assembly, open when the temperature exceeds normal operating
temperature of the Cell. They are all wired in series and power the coil of K4. (K4 is not shown on this Overview)
The coil of K2 is wired through the contacts of K4. When an over temperature switch opens, voltage to the coil of K4
is lost. This will cause K2 to de-energize, and ALL power will be removed from ALL
heaters.
(K4 also signals the Controller to shut the Oven down)
2. Heater Thermocouple (IAS Option)
A Heater mounted thermocouple connected to the Independent Alarm Scanner option. The IAS output contacts are
wired in series with the cell over temperature switches and power to the coil of K4. (K4 is not shown on this Overview)
The coil of K2 is wired through the contacts of K4. When an over temperature condition is sensed, the I.A.S board
contacts open and voltage to the coil of K4 is lost. This will cause K2 to de-energize, and ALL power will be removed
from ALL heaters. (K4 also signals the Controller to shut the Oven down)
3) Heater Thermocouple (Standard)
A Heater mounted thermocouple(s) to sense the temperature of the Heat Cell and connected to the Controller for
heater control.
3) HEATERS:
Each Heater Assembly has two large flat Inconel elements (resistors) mounted between two aluminum plates.
Each pair of elements may be wired in series or parallel, depending on the operating voltage of the oven.
Heater Schematic
See: “Heater Resistance & Replacement
Reference Chart” for resistance values
Technical Service Manual 16 Revision Date: August 2004
HEATING CELL DESCRIPTION
HEATING CELL CROSS-SECTION
CONSTRUCTION: The heat Cells are assembled and sealed as self-contained units with the Fan Motor, and Over
Temperature Switch mounted and wired to terminals, and the Thermocouples (1 or 2) mounted and wired to connectors.
OPERATION: The relatively thick heater assembly has a series of holes allowing heat transfer to the oven gases passing
from the Cell Cavity to the process tunnel.
Recirculation occurs through the low-pressure intakes at the sides of the Cell. These gasses are drawn into the cell
cavity, where they are passed through the heater and back into the process tunnel.
Fan Speed controls the velocity of the heated atmosphere, which influences the heat transfer to the PCB.
INSULATION
EXHAUST
FAN MOTOR
HEATER ASSEMBLY
THERMOCOUPLES
OVER TEMPERATURE
SWITCH
HEAT SLINGER
FAN BLADES
AIR OR
NITROGEN IN
Technical Service Manual 17 Revision Date: August 2004
OVEN CELL ARRANGEMENT
The cells are mounted both above and below the conveyor, as shown, forming a series of “Heat Zones”.
Each Heat Zone circulates heat primarily within itself, thereby maximizing the thermal isolation between zones.
An insulated exhaust plenum mounted under the Bonnet collects gases from the individual upper heat cell exhausts and
conveys the combined flow to the Plant Exhaust System.
An oven contains several heating zones (5,7,8,10, or 12) and 2, 3, or 4 cooling zones. Cooling zones are identical to
heating zones except they have no heating elements and no exhausts (only gas intakes).
A properly operating oven is an inter-dependent system. When a heater or fan malfunctions, the balance and
performance of the oven as a system may be affected. Usually, an irregularity in operation could be the result of any one
(or more) malfunctions.
INSULATED CONTROLLED
EXHAUST PLENUM
TO PLANT
EXHAUST
SYSTEM
CELL 2BCELL 1B CELL 3B
CELL 4TCELL 3TCELL 2TCELL 1T
Zone 1