1.13 BATTERY CHARGING ALTERNATOR1.13.1 Alternator OperationCAUTIONObserve proper polarity when installingbattery. Negative battery terminal must begrounded. Reverse polarity will destroy therectifier diodes in alternator. As aprecautionary measure, disconnectpositive battery terminal when chargingbattery in unit. Connecting charger inreverse will destroy the rectifier diodes inalternator.The alternator converts mechanical and magneticenergy to alternating current (AC) and voltage by therotation of an electromagnetic field (rotor) inside a threephase stator assembly. The alternating current andvoltage is changed to direct current and voltage, bypassing AC energy through a three phase, full-waverectifier system. Six silicon rectifier diodes are used. (SeeFigure 1-17 or Figure 1-18.)1.13.2 Integral Voltage Regulator Operation(12 volts DC)The regulator is an all-electronic, transistorizeddevice. No mechanical contacts or relays are used toperform the voltage regulation of the alternator system.The electronic circuitry should never require adjustmentand the solid state active elements used have provedreliable enough to warrant a sealed unit. The system istemperature compensated to permit the ideal chargingrate at all temperatures.The regulator is an electronic switching device. Itsenses the voltage appearing at the auxiliary terminal ofthe alternator and supplies the necessary field current formaintaining the system voltage at the output terminal.The output current is determined by the load.YellowYellow12Red2Black431. D+ Emulation (Orange)2. #10-24 AC Terminal3. #10-24 Ground Screw4. 1/4-20 Positive Output Cable65 AMPFigure 1-17. 65 Amp Alternator and Regulator P/N 30-00409-02 (<strong>Trailer</strong> <strong>Unit</strong>)32L1B--41. Positive Output(B+)2. Regulator3. 12vdc Test LampTerminal (L)4. Ground TerminalB+70 AMPFigure 1-18. 70 Amp Alternator and Regulator for <strong>Unit</strong>s Built In Europe1-27 62-02884
1.14 REFRIGERANT CIRCUIT DURINGCOOLING (SeeFigure1-19)When cooling, the unit operates as a vaporcompression refrigeration system. The main components ofthe system are the reciprocating compressor, air-cooledcondenser, thermostatic expansion valve, direct expansionevaporator, and liquid line solenoid valve.The compressor raises the temperature and pressureof the refrigerant and it passes through a normally openMain Heat Valve (MHV), through a check valve into thecondenser. The condenser fan circulates surrounding airover the outside of the condenser tubes. Heat transfer isthen established from the refrigerant gas (inside thetubes) to the condenser air (flowing over the tubes). Thecondenser tubes have fins designed to improve thetransfer of heat. This removal of heat causes therefrigerant to liquefy. Liquid refrigerant flows from thecondenser and through a check valve to the receiver.The receiver stores the additional charge necessary forlow ambient operation and for heating and defrost modes.The refrigerant leaves the receiver and flows through amanual receiver shutoff valve (king valve).The refrigerant then flows through the subcooler.The subcooler occupies a portion of the main condensingcoil surface and gives off further heat to the passing air.The refrigerant then flows through a filter-drierwhere an absorbent keeps the refrigerant clean and dry.The refrigerant then flows through the accumulator /heat exchanger and then to the liquid solenoid valves(LSV). These solenoids are electrically energized whenin cooling mode and allow the liquid refrigerant to flowthrough the externally equalized thermostatic expansionvalve (TXV), which reduces the pressure of the liquid andmeters the flow of liquid refrigerant to the evaporator toobtain maximum use of the evaporator heat transfersurface.The evaporator tubes have aluminum fins to increaseheat transfer; heat is removed from the air circulatedthrough the evaporator. This cold air is circulatedthroughout the box to maintain the cargo at the desiredtemperature.The transfer of heat from the air to the lowtemperature liquid refrigerant causes the liquid tovaporize. This low temperature, low pressure vaporpasses into the accumulator tank. The compressor drawsthe vapor out of the accumulator through a pick-up tubewhich is equipped with a metering orifice. This orificeprevents the accumulation of oil in the accumulator tank.The metering orifice is calibrated to control the rate of oilflowing back to the compressor.The vapor refrigerant then enters the compressorpressure regulating valve (CPR), which regulatesrefrigerant pressure entering the compressor, where thecycle starts over.The quench valve opens as required to maintain a116_C (240_F) maximum discharge temperature.1.15 REFRIGERANT CIRCUIT DURINGHEAT AND DEFROST (See Figure 1-20)In heat mode, two technologies can be used: Hot gasheating through the hot gas solenoid valves (HGV1,HGV2 & HGV3) or heating by electric heaters in theevaporator.Heating by hot gas is allowed only if no evaporator isin cooling mode.If two or three evaporators are in heat mode, oneevaporator only will be in hot gas heating. The otherevaporators will be given inductive heating using theelectric heaters in the evaporator.Both hot gas and electric heat are used for defrost.a. Hot Gas HeatingWhen refrigerant vapor is compressed to a highpressure and temperature in a reciprocating compressor,the mechanical energy necessary to operate thecompressor is transferred to the gas as it is beingcompressed. This energy is referred to as the “heat ofcompression” and can be used as the source of heatduring the heating cycle.When in the heat mode, with no evaporators callingfor cooling, the hot gas solenoid valves HGSV1, HGSV2,and HGSV3 could be energized. The main heat valve(MHV) will close, diverting the refrigerant to HGSV1,HGSV2, and HGSV3. The normally closed liquidsolenoid valves LSV1, LSV2, LSV3 will energize andopen. The normally closed receiver pressure valve(RPV), situated in the hot gas line to the receiver willopen. This allows the receiver to be pressurized andliquid refrigerant to flow through the drier and sight glassand pass through any liquid line solenoid valves whichwould be energized. The refrigerant passes through theexpansion valve into the evaporator. At the same timehigh temperature, high pressure gas enters theevaporator via the solenoid valves HGSV (1,2 and 3) togive the required heating. The extra liquid purged fromthe receiver ensures maximum heating capacity in lowambient conditions. The evaporator fan passes the airover the hot refrigerant pipes and distributes heated airinto the cargo space.The hot gas travels through the suction line checkvalve into the accumulator where it is drawn back throughthe compressor pressure regulating valve (CPR) to beginthe process again.When temperature is achieved in all evaporators,they will go into null mode. The compartment with thehighest set point will then take the lead and revert back tocool/heat cycles.b. Principle Of Induction Heating (Electric Heat)A control box recuperates the self indicated currentfrom the electric motor when the unit is driven by thediesel engine. This current energizes electrical heatersmounted inside the evaporator.On standby operation the heaters are directlyenergized by the main electrical supply.The system includes a control box, connected withelectrical cables to the refrigeration unit and to theheaters inside the evaporator .62-028841-28
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