Power Supply

Transcript

CHAPTER POWER SUPPLY 1. FOREWORD ...................................................................................................................................3 2. BATTERIES ...................................................................................................................................4 « Zinc-Lead » batteries ..............................................................................................................4 a. The "car" battery .............................................................................................................4 b. “GEL” or “AGM” or sealed lead battery.......................................................................5 « Cadmium-Nickel » batteries ...................................................................................................5 3. CHARGE of BATTERIES. ...........................................................................................................6 Charge with the mains .................................................................................................................7 Charge with a generator set ......................................................................................................8 Remarks : ......................................................................................................................................8 Charge with solar panels .............................................................................................................8 Mounting principles ..............................................................................................................................9 Example of power output from a solar panel ............................................................................... 11 Remark ........................................................................................................................................ 11 4. MAINTENANCE OF THE BATTERY .....................................................................................12 a. How can you control the state of charge of your battery? .....................................12 b. Maintenance of the battery.............................................................................................13 5. INVERTOR ...................................................................................................................................14 Example of installation ......................................................................................................................14 6. The MAINS PROTECTION UNIT (MPU).............................................................................15 7. EXAMPLES OF CONNECTION OF BATTERIES................................................................15 a. Parallel installation of two batteries .............................................................................15 8. ALIMENTATION OF BATTERY.............................................................................................16 a. Power supply with buffer battery ..................................................................................16 b. Power supply from the mains ...........................................................................................16 c. Example and practical exercise.......................................................................................17 TIPS AND TRICKS ............................................................................................................... 20 2 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 1. FOREWORD Every electrical or electronical appliance requires energy to work. The required electrical power will need to be high or low depending on the type of equipment. For HF stations, the power requirement will be about 25 Amperes. For VHF transmitters, it will only be a few amperes. The required amount of Amperes is variable and is proportional to the power of the transceiver. Your power supply must be able to supply a current, which must be superior to the power required to run the appliance. All transceivers used by MSF work on 12 Volt Direct Current (DC) The power is usually supplied by batteries, which are charged by a source of energy. This source of energy can be solar panels, a generator set, or the mains power. Only rely on power supplied by the mains when you are certain there will be no sudden power cuts. Even in this case, you still need to control the quality of the supplied current by using a stabilized power supply. Most problems encountered in field radio installations are caused by improper or defective power supplies. A regular maintenance of your power supply system will avoid these problems. MSF HF and VHF Kits do not contain batteries. Batteries and battery chargers can be ordered separately as articles or power supply modules . All HF and VHF kits work on 12 V DC. 3 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 ELECTRICAL SYMBOLS CURRENT ALTERNATIVE ABBREVIATION AC SYMBOL ~ DIRECT DC = EXAMPLE MAINS 110V or 220 V 12V BATTERY CONNECTIONS Cable without polarity POLARIZED CABLES RED =POSITIVE BLACK = NEGATIVE Or less frequently BLUE=POSITIVE BROWN=NEGATIVE 2. BATTERIES MSF uses two types of batteries, "Acid-Lead" and "Nickel-Cadmium" batteries. « Acid-Lead » batteries There are two types of « Acid-Lead » batteries: a. The "car" battery This is the traditional car battery. To work, it must contain a mixture of water and acid. This mixture is called electrolyte. Water, and water only, evaporates. It is therefore necessary to periodically check the electrolyte level, and if necessary, to add distilled water to keep a correct level. The correct level of electrolyte is when the liquid covers the battery plates by about 1 cm. ☺ Never add acid. If it isn't possible to find distilled water, clean rainwater can be used but NEVER use tap water. In certain Arabic-speaking countries, the liquid called "battery water" is in fact a mixture of 4 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 water and acid. It is therefore important to check the content. If a few drops spilled on the ground produce bubbles, then the liquid contains acid. Transport of batteries by air is problematic. The acid must be transported in a sealed waterproof container, separated from the battery. The battery itself has to be manipulated carefully. These batteries have the advantage of being cheap. An acidometer is necessary to check the water / acid mixture. Be carefull ! Certain “acid-lead” batteries abusively carry the indication “maintenance free”. In fact, their vent plugs are hidden, and very difficult to identify. The electrolyte level in these batteries needs to be checked. b. “GEL” or “AGM” or sealed lead battery This type of battery doesn't contain liquid electrolyte and can be transported by air without restrictions. The price however is three times higher than the price of a traditional battery. It doesn't require maintenance and is perfectly adapted to recharges by solar panels. It doesn't withstand deep charge / discharge cycles. It is not suited for starting vehicles. Note: As no maintenance is needed, this type of battery is perfectly suited for powering radio installations. Unfortunately, these batteries are more expensive than « Acid-Lead » batteries ☺ Advice : Use "gel" type batteries in radio installations. « Cadmium-Nickel » batteries This type of battery equips VHF handsets, portable computers, and satellite communications equipment. They are built specifically to suit the power needs of the particular equipment they are made for. Refer to the notice supplied with the equipment. Beware of the "memory effect". When these batteries are subjected to many incomplete charge/discharge cycles or are continuously being charged, a temporary loss of capacity is created. The only way to counter this effect is to ensure one or more complete discharges of the battery. Using a car light bulb is a clever way to completely discharge a battery, and allows you to check the battery is completely empty before charging it again. 5 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 These batteries unfortunately have a shorter life span than the « Acid-Lead » batteries and there fore need to be supervised closely. The number of complete charge / discharge cycles will usually not exceed 500 cycles. 3. CHARGE of BATTERIES. The energy stored in a battery allows the supply of a given current (A) during a certain amount of time (H). This capacity is expressed in Amperes/Hour (AH). If a battery has a capacity of 80 Amperes/Hour, it will theoretically deliver : - A current of 80 Amperes during one hour - Or a current of 40 Amperes during 2 hours, etc. In practice, it is dangerous to discharge a battery completely. Complete discharges considerably reduce the life expectancy of the battery. It is estimated that in order to work well, a battery cannot be discharged over 50 % of its total capacity. This means that a completely charged 80 AH battery will deliver a maximum power of 40 AH in normal working conditions. Example : For the ICOM 700TY transmitter MODE CONSUMPTION OF HF TRANSMITTER RECEPTION 1.6 A TRANSMISSION 30 A CAPACITY OF THE BATTERY 80 AH 80 AH IDEAL MAXIMUM CAPACITY (50%) TIME AVAILABLE 40 AH 40 AH +/- 25 HOURS +/- 1 HOUR To charge a battery, we use a battery charger which can be powered by various power sources (mains power, generator set, solar panels,…) During the charge, an electrochemical reaction happens within the battery, which liberates hydrogen. This is a highly explosive gas in the air, and care should be taken not to submit it to a spark, an open flame or a heated metal or wood piece. Take the following precautions: - unscrew and remove all the vent plugs on the battery so as to liberate the gas and let it dilute in the air - only recharge a battery in a well ventilated room - avoid approaching a flame or a spark close to the filling holes, where the gas is most concentrated. Never check if the electrolyte is releasing hydrogen (gas bubbles) with a lighter. There is a RISK OF EXPLOSION 6 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 Charge with the mains If you have city power (110 V - 220 V AC), you can plug the battery charger directly on this power supply. ALIMENTATION 220V / 110V AC - victron energie on float boost CHARGER on VOLT off BATTERY 12 VOLT AMP PALLAS 12 15 + Note : Certain chargers are equipped with a 24 Volt / 12 Volt switch. Check the position of the switch before using the charger. In theory, a 10 AH charger will need 8 hours to completely charge an 80 AH battery, which will discharge in 4 hours when it powers a transmitter consuming 20 Ampere. The charge time must equilibrate the discharge time. Practically, the charge time will need to be increased by +/- 20% because there is a loss of energy in the electrical cables and in the charger itself. An automatic charger can stay connected permanently. It is the state of discharge of the battery which controls the initiation of a new charge cycle. 7 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 Charge with a generator set A generator set supplies a voltage of 220 V AC. The battery charger is connected to this source and charges the battery. In theory, with a 10 AH charger, you will need to have the generator set running during 8 hours to recharge an 80 AH battery. The use of a generator set is thus a rather expensive solution. Remarks : - The generator set is powered by an engine, which must be maintained. Check oil levels, change the oil after a given number of working hours, clean the spark plugs, … (refer to the maintenance squedule supplied with the generator). - On certain generator sets, you will find a 12 Volt outlet. Never use this outlet to power a radio or to charge a battery (except in emergency situations) as the generator is not equipped with a charge regulator. Charge with solar panels Solar panels transform solar energy into electrical energy. As there is a lot of sunshine in Africa, this source of energy is certainly a good solution to energy supply problems and should be considered as an option. However, care must be taken to insure a good installation, both in terms of orientation, as in terms of inclination of the panels. Maintenance is limited to regular cleaning of the panels to insure maximum output (clean them with clear water once a week). ATTENTION : Solar panels are fragile. Think about protecting them from shocks from falling branches or stones. This protection can be insured with wire mesh placed twenty centimeters above the panels. 8 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 Mounting principles REGULATOR SOLAR PANELS TO PRIVATE USING TL lamp - + BATTERY 12V The regulator has two functions: - Limit the charge and discharge depending on the state of the battery and the power requirement of the consumers. - Regulate the voltage. BP SOLAR LK System Controler Charge -+ Solar Array Battery Low - + Battery Overload/ Load Disconnect -+ -+ Load Outputs 9 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 There are 3 indicators on the regulator, a red, a yellow and a green LED. If during the day, the yellow LED is on, this means the charge is not sufficient. If, after having checked the cleanliness of the solar panels, the yellow or red LED remain on, then you will need to complete the charge of the batteries with another source of power (generator or mains power). Three lights mounted on the front panel of the system controller indicate status as follows. Indicator status GREEN light OFF continuously INDICATION No power from solar panel GREEN light ON continuously Battery charging in progress Battery charged GREEN light flashes periodically YELLOW light ON continuously Battery in poor state of charge. YELLOW and RED lights ON continuously Battery in poor state of charge. RED light flashes periodically Overload RED light ON All 3 lights flash rapidly. Controller OUT Battery disconnected. Array connected. Recommended Action Check connexions from solar panel. Check if solar panel is always there (thieft). Reduce load of battery. Disconnect one or more elements connected to battery. ( VHF charger, Invertor,…) Reduce load of battery. Disconnect one or more elements connected to battery. ( VHF charger, Invertor,…) Load disconnected. Repair load fault. Replace Controller. Repair/Replace battery connections. The transmitter is connected directly to the batteries as it can consume up to 25 Amperes, and this amount of current would destroy the regulator. REMARKS : - Respect polarities - Keep distances between solar panels, regulator and batteries as short as possible to minimize power losses in the cables by keeping these as short as possible. 10 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 Example of power output from a solar panel • • If installed correctly, one solar panel (50 x 90 cm) can produce an average of 50 Watts per hour. In Africa, 6 hours of intense sunlight can be taken as an average for a sunny day. This means that the solar panel can produce up to 300 Watts per day, and will allow to work: o A Codan transceiver during 20 hours in stand-by, and 1 hour transmission or o 2 neon lights (TL) during 10 hours or o 1 portable computer during 48 hours. ATTENTION : The regulator provides 15 Amperes in 12 Volts. The formula for power gives : POWER = VOLTAGE in Volts(V) X CURRENT in AMPERES (I) = 12 Volts X 15 Amperes = 180 WATTS If the equipment, or equipments, you are powering require more than 180 Watts, the regulator will be destroyed. It is important determine the total power requirements of your installation to accurately. Example : - 17 neon lights of 10 W each = 170 W OK - 1 fridge of 120W + 4 neon lights of 10W = 160W OK - 14 neon lights of 10W + 1 bulb of 60W = 200W NOT OK Please note that on each electrical equipment there is normally a plate indicating the voltage (V) and the power (W) consumed by equipment. Remark Fuses are meant to protect an electrical equipment. Their breaking capacity is calculated with a safety margin. If they blow regularly although their rating is the one prescribed by the manufacturer, this means that there is a serious problem in the equipment or a short circuit in the cables. Do not try to solve the problem by replacing the fuse with one which has a higher rating. You must try to find the reason why the fuse blows, which can be that the fuse had an 11 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 in-adapted (too low) breaking capacity, or that there is a cable polarity inversion. If the problem repeats itself, the equipment is faulty. In addition, with low voltage equipment, high current will need to travel through the cables to power the equipment. This means that the cable must be of adequate thickness in relation to its' length. The table below gives a few indications. DISTANCE TO THE BATTERY 2 meters 3 meters 4 meters 5 meters MINIMUM THICKNESS OF THE CABLES 4 mm² 6 mm² 7.5 mm² 10 mm² DIAMETRE OF THE CABLES 2,2mm 2,8 mm 3,15 mm 3,6 mm 4. MAINTENANCE OF THE BATTERY a. How can you control the state of charge of your battery? Before measuring the state of charge of your battery, you must first disconnect all cables from the battery poles. Method with a Voltmeter : - Measure the voltage with a precise voltmeter If the battery is fully charged, the voltage will be of at least 12.7V If the battery is empty, the voltage will be 11.7 Volts or less ☺ Note 1 These readings give only an indication on the current state of charge of the battery and do not indicate the total available power (Ampere/hours). Older or damaged batteries can give you a voltmeter reading that they are fully charged, however, their real available power can be substantially reduced. 12 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 Method with an acid hydrometer : - Measure the density with the hydrometer. Most hydrometers are graduated as follows Completely charged 1,28 Half charge 1,2 Empty 1,1 ☺ Note 2 To evaluate the state of a battery (available capacity), first insure it is fully charged, then: - Connect an important consumer to the poles (like a Codan transceiver) - Place a voltmeter to the poles of the battery and record the reading. - If, upon transmitting, a rapid drop in voltage occurs, the battery is dead. - Replace the battery in this case. b. Maintenance of the battery - "Car" type batteries and all batteries with liquid electrolyte require the acid levels to be checked periodically. Restore the electrolyte level with distilled water. If distilled water is not available, use clean rain water. Check the batteries to find traces of corrosion. If there are traces of corrosion, clean the poles with a little warm water or a slightly caustic solution. It is important to keep the battery poles clean to guarantee good contacts. Apply a thin coat of paraffin or grease on the poles to avoid corrosion. 13 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 5. INVERTOR An invertor is an electrical equipment which transforms a 12 Volt DC current coming from a battery into 220 Volts AC. Thanks to this system, we can connect a 220 V appliance like a printer or a computer by supplying it with 220 Volts AC (like if you had a wall socket) ATTENTION : 6. This equipment has a limited power output (300 Watt and 500 Watt). You need to check you do not exceed these limits or you will destroy the invertor. 7. Only connect small power consumers like portable computers, printer or VHF battery charger to the invertor 8. Install the invertor in a well ventilated place 9. Respect the polarities on the 12 Volt DC connections (red cable + , black cable -) Example of installation INVERTOR CHARGER BATTERIES 12V victron energie victron energie on float boost 15 - INVERTER PALLAS 12 AMP PALLAS 12 VOLT off + 15 AMP on VOLT CHARGER + 14 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 6. The MAINS PROTECTION UNIT (MPU) This cheap device protects your equipment from power surges. When the voltage exceeds (or falls below) the set limits, the protection unit will cut off the power to the connected electrical equipment. Technical specifications : Voltage: Disconnection limits : 220 Volts AC High 265 Volts Low 170 Volts High 260 Volts Low 185 Volts 10 A Reconnection limits : Max. available current Max power 2200 W ☺ Advice : This voltage limiter is highly recommended to protect fragile and / or expensive electrical equipment. 7. EXAMPLES OF CONNECTION OF BATTERIES a. Parallel installation of two batteries You can double the capacity of a battery without changing the voltage by connecting two batteries in parallel as shown below: + + - - 12 VOLT 60 Amps/Hour 12 VOLT 60 Amps/Hour Telecom Guideline MSFB 12 V / 120 Ah CHARGE ( TRANSCEIVER...) 15 Chapter POWER SUPPLY 01/01/2002 ☺ The cables between batteries must be as short as possible. The diameter of the cables must be larger than the one of the power cables supplied with the transceivers. 8. ALIMENTATION OF BATTERY a. Power supply with buffer battery The most usual setup is the following one: The transceiver draws the energy from two 12 Volt batteries installed in parallel. A charger is connected to the mains power or a generator set and charges the batteries. This setup uses the batteries as a buffer. ALIMENTATION 220V / 110V AC victron energie on - - CHARGE 12 VOLT / 120 Ah float boost CHARGER on BATTERY 12 VOLT BATTERY 12 VOLT VOLT off AMP PALLAS 12 15 60 Ah 60 Ah + + b. Power supply from the mains In some rare cases where the power from the mains is available, the use of buffer batteries is not necessary. In this case, a stabilized power supply will be used which transforms the 220 16 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 Volt (or the 110 V), into 12 Volt DC. All you need to do is to plug the power supply into the mains, and connect the red and black power supply cable of the radio to the power supply. For example, the Power Supply PS 35 from Icom delivers 12 Volts and a maximum of 25 Amperes. There is also a more powerful model, the PS 60. Remark: During transmission, the power supply will heat up. The cooling fins at the back of the equipment allow it to cool down. Make sure the power supply is well ventilated and that it can cool efficiently. 220 V AC ALIMENTATION 220 V AC / 12 V DC CHARGE TRANSFORMATOR + - c. Example and practical exercise Consider a normally equipped radio room with : An HF radio A VHF radio Three VHF battery chargers A modem, a computer and a printer for the radio telex A Mini M satellite phone An invertor A neon light 17 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 If you want these equipments to function automomously, you will need to consider their power combined consumptions. The following table will allow you to size your actual power requirements depending on the equipment you have. Average hourly consumption HF radio (Codan or Icom) VHF radio ( Yaesu) VHF battery charger Modem PACTOR II Computer type TOSHIBA 4090 Printer Satellite telephone Invertor 300 W Neon light Stby Use Stby Use Consum. Consum. Consum. 0.4 A/h 50 min. 25 A/h 10 min. 0.6 A/h 50 min. 12 A/h 10 min. 1 A/h 3 charg. 0.25 A/h 6.25 A/h Consum. 0.25 A/h Stby 0.025 A/h Use 0.5 A/h Data 1.3 A/h Stby 0.5 A/h Use 25 A/h Consum. 0.6 A/h 40 min. 10 min. 10 min. 30 min. 30 min. 50x(0.4 :60) 10x(25 : 60) 50x(0.6 : 60) 10x(12 : 60) 40x(0.025 : 60) 10x(0.5 : 60) 10x(1.3 : 60) 30x(0.5 : 60) 30x(25 : 60) The total amperes consumed in one hour will be : 0.33 4.1 0.5 2 3 0.25 6.25 A A A A A A A 0.25 0.01 0.01 0.2 0.25 12.5 0.6 A A A A A A A 30.25 A We saw above that it is not good for the batteries to be discharged more than 50 % of their total capacity. Given that we need to supply 30.25 Amps, we require: 30.25 A x 2 = 60.5 A We will need at least two batteries of minimum 80 A To charge these batteries A 25A battery charger in practice delivers a current of 20 A per hour. The two fully charged batteries have a total available capacity of 40 A ( 50% of 80A) and the consumption of the equipment is of 30.25 A per hour. We can see directly how important it is to charge the batteries continuously. If you have city 18 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 power, this will not be problematic. However, in other circumstances, it will be necessary to supply the energy to the charger via a generator or solar panels. 19 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002 TIPS AND TRICKS Chargers and invertors can cause interferences in radio equipment. In some cases, it is necessary to turn off these equipments to allow a normal radio communication. It is always recommended to place these equipments as far as possible from the transceivers and outside the radio room if possible. Invertor and charger must be connected to the earth. The polarity of connections with DC is very important. The red cable represents the positive polarity (+), and the black cable, the negative polarity (-). Not respecting the polarity will cause the equipment to be permanently damaged. Always use the original cables. Never replace these cables with thinner cables. A considerable voltage drop can occur with thin cable and create a fire hazard. Periodically examine all cables and ensure that all connections are clean and sound. All connections must be soldered. Power supply cables must NEVER be shortened. All power supply cables should be bundled together between the radio and the battery. Do not loop power supply cables, as these loops produce magnetic fields, which cause interferences in the radios. If you connect two batteries in parallel, always use identical batteries (type, capacity and age). Beware of short circuits and never deposit metallic objects, which could cause the poles of the battery to connect. Most trucks and certain TOYOTA Land Cruisers are equipped with a 24V DC system (two 12V batteries in series). If you need to connect an equipment which uses 12 Volts, you will have to install a voltage convertor (24 VDC to 12 VDC) For mobile installations, always connect the CODAN fuse on the red power supply cable going from the battery to the radio and install it as close as possible to the battery. 20 Telecom Guideline MSFB Chapter POWER SUPPLY 01/01/2002