Vogt TUBE-ICE 05TA, Service Manual

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05TA Service Manual
SERVICE OPERATIONS
8/13/01
9-5
The solid state sensor protectors provide excellent protection against high motor temperatures
resulting from locked rotor, loss of charge, or motor overload. The combination of low voltage
sensing and time delay provide positive protection against low voltage conditions which can occur in
the pilot circuit in the event of a single phase condition on a three phase circuit.
The low voltage protection feature removes the compressor from the line in the event of low voltage
("brown-out") conditions. The module locks the compressor off the line until the voltage rises to the
cut-in setting. The time delay provides a two minute delay before restarting each time the power
circuit is opened. Pressing the start button before the two minute delay will have no effect. Service
and test personnel must be alert to this feature since it is possible in checking the compressor or
system, power may be applied, disconnected, and reapplied in less than two minutes. In such case the
time delay feature will prevent operation until the time delay has expired and this may be
misinterpreted by service personnel as a module malfunction.
The time delay would be energized in the event of a discharge pressure or short circuit protector trip,
low voltage, or a break in the power supply to the module. The time delay is not energized on
opening of the high or low pressure switches.
There are two major components in the protection system.
1. The protector sensors are mounted internally in the motor windings. The characteristics of the
sensor are such that a change in temperature causes a change in the sensor's electrical resistance.
2. The control module is a sealed enclosure containing a relay or triac, transformer, and several
electronic components. Leads from the internal motor sensors are connected to the module as shown
on the wiring diagrams. While the exact internal circuitry is quite complicated, basically the module
senses the change in resistance of the sensors. As the motor temperature rises or falls, the resistance
also rises or falls, triggering the action of the control circuit at predetermined opening and closing
settings.
Protector modules have two terminals on the module marked "T1-T2" or "L1-L2". These are to be
connected to a power source of the proper voltage, normally the line terminals on the compressor
motor contactor or the control circuit transformer as required.
The control circuit is to be connected to the two terminals marked "control circuit". When the proper
voltage is present and the motor temperature is within limits, the "M1-M2" circuit is closed and the
pilot circuit is energized after the two minute off-cycle time delay. If the motor temperature rises
beyond safe limits, the resistance of the motor sensors rises, causing the control circuit to open. The
solid state module cannot be repaired in the field, and if the cover is opened or the module physically
damaged, the warranty on the module is voided. No attempt should be made to adjust or repair this
module, and if it becomes defective, it must be returned intact for replacement.
Electronic Motor Protector High-Potential Testing. The solid state sensors and the electronic
components in the solid state module are delicate and can be damaged by exposure to high voltage.
Under no circumstances should a high potential test be made at the sensor terminals with the sensor
leads connected to the solid state module. Even though the power and pilot circuit leads are not
connected, the module can be damaged.