B&K 1794 instruction manual Output Capacitance, Reverse Voltage Loading, Reverse Current Loading

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4.6OUTPUT CAPACITANCE :

Internal capacitor C3 ( L1791-FP-CNT-0603 PCB ) connected across the output terminals of the power supply, helps to supply high current pulses of short duration during constant voltage operation. Any capacitance added externally will improve the pulse current capability, but will decrease the safety provided by the constant current circuit. A high current pulse may damage load components before the average output current is large enough to cause the constant current circuit to operate.

The effects of the output capacitor during constant current operation are as follows: a.The output impedance of the power supply decreases with increasing frequency

b.The recovery time of the output voltage is longer for load resistance changes.

c.A large surge current causing a high power dissipation in the load occurs when the load resistance is reduced rapidly.

4.7REVERSE VOLTAGE LOADING :

A diode CR1 is connected across the output terminals. Under normal operation, the diode is reverse biased (anode connected to the negative terminal ). If a reverse voltage is applied to the output terminals ( positive voltage applied to the negative terminal), the diode will conduct, shunting current across the output terminals to the forward voltage drop of the diode. This diode protects the series transistor and the output electrolytic capacitors.

4.8REVERSE CURRENT LOADING :

Active loads connected to the power supply may actually deliver a reverse current to the power supply during a portion of its operating cycle.

An external source cannot be allowed to pump current into the supply without loss of regulation and possible damage to the output capacitor. To avoid these effects, it is necessary to preload the supply with a dummy load resistor so that the power supply delivers current through the entire operation cycle of the load device.

4.9EXTERNAL PROGRAMMING :

Remote external programming can be achieved changing the external program link on rear panel and connecting a variable resistor of 5K across the terminals as shown on the rear panel.

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Contents BK Precision Limited Two Year Warranty Table of Contents Section General Information Description Output ON/OFF SwitchLimit Setting Remote Programming With External 5K PotSection Specifications Section Installation Input TAP Selection for 230V Operation Repackaging for ShipmentSection Operating Instructions Readjust the current limit in the remote sensing mode Reverse Voltage Loading Output CapacitanceReverse Current Loading USE the Proper Power Cord Operators Safety SummaryTerms in this Manual Terms AS Marked on Equipment Do not Service Alone Servicing Safety SummaryFor Qualified Service Personnel only USE Care When Servicing with Power onTrouble Shooting Techniques Section Service Instruction GeneralServicing shall be done only by Qualified personnel Repairs & Maintenance Page REF. PCB no PIN no Parts Ordering & ReplacingPage Page Fuse Blows Fault Finding ProcedureFuse Blows Unregulated O/P Voltage Unregulated O/P VoltageNo Output Voltage No O/P VoltageNo DPM Indication No DPM IndicationDPM not Read Unit not Take Current Unit not Take CurrentUnit Directly Goes to CC Unit Directly Goes To CCNo Current Control No Current ControlPoor Line Regulation Poor Line RegulationCV, CC, LED not Glow Poor Load RegulationPoor Load Regulation Remote Sense not OK External Programming not OKExternal Programming Not OK 1KPF/100V, Disc Section Part List & SchematicsL1791-FP-CNT-0603 PCB Assy 2P2W SW Push ButtonSW1 Grey Colour CAP for Push Switch SW2 SW3 PS-PREG-1791-0503 PCB AsslyDPM/01 REV 01 X PS-AUX-DC-L1791-0503 PCB Assly PS-PWR-L1791-0703A PCB AsslyMain Chassis Assly Front Panel AsslyBack Trough Assly Front Panel Layout Back Panel Layout TOP View Bottom View of Model 1790 Front Panel Control PCB of 1790 Power Module PCB of 1790 PRE Regulator / AUX. P/S PCBs 1790 Service Information Precision CorpPrecision Corp
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