GB1409654A - Method of testing alternators - Google Patents

Abstract

1409654 Testing alternators LUCAS ELECTRICAL CO Ltd 11 Sept 1972 [24 Sept 1971] 44568/71 Heading G1U An alternator having a wound field 25 and a stator 11, 12, 13 (e.g. a car alternator) is tested by applying an A.C. voltage to the field winding and monitoring the signal induced in the stator winding. As described the stator signal is extracted via a fullwave rectifier either 14, 15 or 16, 15, and a multisocket 17, and if the resulting signal is either too low in amplitude, or if its waveform is too irregular, then a fault lamp 77 is energised. The test device, which includes a voltage source 27, control switches 38, 51, 52, and "fault", and "pass" indicator lamps 71, 78, is connected to the alternator under test by a multi-pin plug 17a, correspondingly referenced pins and sockets, e.g. 18a and 18, coming together. In operation, with switches 51, 52 in their positions shown, a start key 38 in depressed causing firstly a power line 33 to be connected via a resistor 39 to a contact 41, and then with further depression of the key 38, the line 33 is connected to both the contact 41 and a line 37. Application of power to contact 41 energises a relay 42 to close a normallyopen contact 43 and apply power, from a winding 31 via normally closed contacts 44, to the field winding 25. The resulting signal induced in the stator windings 11, 12, 13, is rectified by diodes 16 and applied, via contacts 51, 52 across a resistor 53. When key 38 is fully depressed, and power is applied to line 37, if the voltage across resistor 53 is sufficiently large a transistor 61 conducts sufficiently to retain transistors 68 and 71 non-conductive and conductive respectively, so that neither of two SCR's 75, 76 fires and the "pass" lamp 78 is energized. If, however, the average conduction of transistor is not sufficiently heavy, a Zener diode 66 will conduct, resulting in the firing of both SCR's 75, 76 and the energization of the "fault" lamp 77. Actuation of switch 52 selects diodes 14 instead of diodes 16, and actuation of switch 51 selects a resistor 54 instead of resistor 53, these resistors being related to the rating of the alternator under test. Further, if when the field winding 25 is first energised a leak to earth should occur, then a relay 46 is energised to open the contact 44 and prevent any damage.