• Document: MEAN WELL SPS USER MANUAL
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MEAN WELL SPS USER MANUAL 1. INPUT 1.1 INPUT VOLTAGE Switching Power Supplies (SPS) are widely used all over the world. Many types of products are available for both alternating and direct current input. Before using any power supply, ensure that the output voltage and current is suitable for the intended load. Verify the correct input connections and any other conditions that might affect the power supply’s operation. If an input voltage is applied which is different from the power supply’s rating, the unit may be damaged. Also remember that if the input voltage wave is distorted, the power supply may not operate normally, even though the measured voltage is within the allowable range. A Meanwell inverter can be used but it must be over-rated due to the inrush current at switch on. For all Mean Well Safety Approved Models refer to the label on the power supply for the input voltage range. Fig. 1 1.2 INPUT CURRENT Standard switching power supplies directly rectify the input Alternating Current (AC). Most standard units are capacitor-input- type, rectifying systems in which rectified current flows through the smoothing or filtering capacitor. Therefore, the input current is determined by the output power, input voltage, power factor, and efficiency. Fig. 2 The power factor of the typical switching power supply is between 0.4 and 0.6, for Active PFC (Power Factor Correction) units it’s greater than 0.9 at full load. 1.3 INRUSH CURRENT When power is applied, a large current flows to charge the input smoothing or filter capacitor. This current is called the “inrush current”. The value of the inrush current varies according to the power-on timing and the presence or absence of the inrush current protection devices. The inrush current is many times larger than the normal input current. The more switching power supplies used in the same system, the larger the inrush current. Please ensure that fuses, switches, and other parts connected to the input supply side are appropriately selected. Also, when powering switching power supplies from a DC to AC inverter you will need to allow for this inrush current and make allowance for the switch-on sequence of multiple supplies. www.procontechnology.com.au 1 Phone: (03) 98306288 Fig. 3 If the switching power supply fuse is blown, do not replace the fuse and operate the unit before rectifying the problem that caused it to fail – otherwise further damage may occur to the power supply! Always replace the fuse with the same rated type. Always remove power to the unit before attempting to replace the fuse. WARNING: High voltage inside - do not open the case. Always return to an authorized agent for any repair. 2. OUTPUT 2.1 MAXIMUM OUTPUT POWER Maximum power output (Pout) is defined as: Pout = Vout x Iout Where Vout is the output voltage and Iout is the output current. Most power supplies allow Vout to be adjusted. However, Pout must remain constant. Therefore, if Vout is increased, the maximum Iout must be decreased. E.g. The RS-50-5 power supply has an output voltage of 5 volts and an output current of 10 amps. The maximum power output is 50 watts. The adjustable voltage range is 4.75 volts to 5.5 volts. If the output voltage is adjusted to 5.5 volts, the maximum output current can be calculated by: Iout = Pout / Vout i.e. Iout = 50 watts / 5.5 volts = 9.09 amps. The output voltage can also be adjusted lower than 5 volts. However, due to the design of the output circuit, exceeding the 10 amp maximum output is not recommended as over current protection may activate. Some multiple output power supplies have a Current Range that exceeds the Output Rated Current. The table below has some specifications for the RD-65A (dual output) power supply. Output Output Rated Output Current Channel Voltage Current Range 1 5V 6A 0.3 ~ 8A 2 12V 3A 0.2 ~ 4A Ch. 1 can output 8 amps but the total power output cannot exceed 66 watts. For example, if Ch. 1 was operated at a 7.5 amp output, the Ch. 2 output current would have to be reduced to remain within the 66 watt limit. The total output power for Ch. 1 would be: (5 volts) x (7.5 amps) = 37.5 watts. This would allow 28.5 watts for Ch. 2. The total current available for Ch. 2 is: (28.5 watts) / (12 volts) = 2.375 amps. 2.2 OVERCURRENT PROTECTION (OCP) / OVERLOAD PROTECTION

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