7.3.4. Control checks of the generator

Check of the generator at the stand
Check at the stand allows to define serviceability of the generator and compliance of its characteristics nominal. At the checked generator of a brush rings have to be ground well in by pure to contact rings of a collector, and.

Fig. 7.7. The scheme of connections for check of the generator at the stand: 1 – control lamp of 12 V, 3 W; 2 – generator; 3 – voltmeter; 4 – rheostat; 5 – ampermeter; 6 – switch; 7 – rechargeable battery

Install the generator on the stand and execute connections as shown in fig. 7.7. Turn on the stand electric motor, 4 establish by a rheostat tension at the exit of the generator of 13 V and finish the frequency of rotation of a rotor up to 6000 min.-1. Let's the generator work on this mode not less than 10 min., and then measure return current. The serviceable generator has to have it not less than 80 And.
If the measured size of the given current is much less, then it speaks about malfunctions in windings of the stator and a rotor or about damage of gates. In this case careful check of windings and gates is necessary to define the place of malfunction.
Tension at the exit of the generator is checked with a frequency of rotation of a rotor of 5000 min.-1. 4 establish by a rheostat current of return 15 A and measure tension at the generator exit which has to be 13,2-14,7 B at a temperature of air and the generator (25 ±10) °C.
If tension does not keep within the specified limits, then replace the brush holder with tension regulator new, obviously serviceable, and repeat check. If tension is normal, then, therefore, the old regulator of tension is damaged and it needs to be replaced. And if tension still does not keep within the limits stated above, then it is necessary to check windings and gates of the generator.

Check of the generator electronic oscillograph
The oscillograph allows in a form of a curve of the straightened tension precisely and to quickly check serviceability of the generator and to define the nature of damage.

Fig. 7.8. The scheme of connections for check of the generator an oscillograph: 1 – switch; 2 – generator; 3 – voltmeter; 4 – rheostat; 5 – ampermeter; 6 – switch; 7 – rechargeable battery

For check collect the scheme according to fig. 7.8. Disconnect a wire of the general conclusion of three additional diodes from the plug D + the regulator of tension and take measures that the tip of the disconnected wire did not become isolated with a mass of the generator. + the regulator attach a wire from the rechargeable battery via the switch 1 to the plug D. Thus, the winding of excitement will eat only from the rechargeable battery.
Turn on the electric motor of the stand and finish the frequency of rotation of a rotor up to 1500–2000 min.-1. The switch 6 disconnect the rechargeable battery from the B+ plug of the generator and 4 establish by a rheostat current of return 10 A.

Fig. 7.9. A form of a curve of the straightened generator tension: I \the generator is serviceable; II \the gate is punched; III \break in a gate chain (a stator winding)

Check on an oscillograph tension on the generator B+ plug. At serviceable gates and a winding of the stator the curve of the straightened tension has the sawtooth form with uniform teeth (fig. 7.9, I). If there is a break in a winding of the stator either break or short circuit in gates of the vypryamitelny block — the curve form sharply changes: uniformity of teeth is broken and deep hollows (fig. 7.9, II and III) appear.

Fig. 7.6. Scheme of connections of system of the generator: 1 – rechargeable battery; 2 – generator; 3 – assembly block; 4 – the control lamp of a charge of the rechargeable battery located in a combination of devices; 5 – ignition switch

Having checked tension curve form on the B+ plug of the generator and having convinced that it has a normal appearance, check tension on the generator plug D at the disconnected wire from the plug D + tension regulator. The plug D is the general conclusion of three additional diodes (see fig. 7.6) feeding an excitement winding during the operation of the generator. Tension curve here too has to have the correct sawtooth form. Irregular shape of a curve demonstrates damage of additional diodes.

Check of a winding of excitement of a rotor
The winding of excitement can be checked without removing the generator from the car, having removed only the protection cover and the regulator of tension together with the brush holder. Having smoothed out if necessary a grinding skin contact rings, an ohmmeter or a control lamp check whether there is no break in a winding of excitement and whether she becomes isolated with a weight.
Check of the stator
The stator is checked separately, after removal of the vypryamitelny block.
First of all check an ohmmeter or by means of a control lamp and the rechargeable battery whether there are no breaks in a winding of the stator and whether its rounds on "weight" become isolated.
Isolation of wires of a winding has to be without traces of an overheat which occurs at short circuit in gates of the vypryamitelny block. Replace the stator with such damaged winding.
At last, after dismantling of the generator it is necessary to check the special defectoscope whether is not present in a winding of the stator of short-circuited rounds.

Check of gates of the vypryamitelny block 
The serviceable gate passes current only in one direction. Faulty — can or not pass current (break of a chain) at all, or to pass current in both directions (short circuit).
In case of damage of one of gates of the rectifier it is necessary to replace entirely the vypryamitelny block.

Fig. 7.10. Schemes for check of gates of the rectifier: 1 – rechargeable battery; 2 – control lamp; 3 – generator; I \check of at the same time "positive" and "negative" gates; II \check of "positive" gates; III \check of "negative" gates

Short circuit of gates of the vypryamitelny block can be checked without removing the generator from the car, previously having disconnected wires from the rechargeable battery and the generator and having removed a casing from a back cover of the generator. Also the wire is disconnected from a conclusion of D + tension regulator. It is possible to check an ohmmeter or by means of a lamp (1–5 W, 12 V) and the rechargeable battery, as shown in fig. 7.10.

       NOTE
For the purpose of simplification of fastening of details of the rectifier three gates (with a red tag) create on the plus case of the straightened tension. These positive gates and they are pressed in one plate of the vypryamitelny block connected to a conclusion of "B+" of the generator. Other three gates ("negative" with a black tag) have on the minus case of the straightened tension. They are pressed in other plate of the vypryamitelny block connected to weight.


At first check whether there is no short circuit at the same time in "positive" and "negative" gates. For this purpose "plus" batteries through a lamp connect to a generator B+ clip, and "minus" to the case of the generator (fig. 7.10, I). If the lamp burns, then "negative" and "positive" gates have short circuit.
For check of short circuit in "positive" plus gates of the battery through a lamp connect to a generator B+ clip, and "minus" – to one of phase conclusions of a winding of the stator (fig. 7.10, II). Burning of a lamp will indicate short circuit of one or several "positive" gates.
Short circuit of "negative" gates can be checked, having connected battery "plus" through a lamp to one of phase conclusions of a winding of the stator, and "minus" with the case of the generator (fig. 7.10, III). Burning of a lamp means short circuit in one or several "negative" gates. It is necessary to remember that in this case burning of a lamp can be also a consequence of short circuit of rounds of a winding of the stator on the generator case. However such malfunction meets considerably less than short circuit of gates.
The break in gates without dismantling of the generator can be found or an oscillograph, or when checking the generator at the stand on considerable decrease (for 20–30%) sizes of the given current in comparison with nominal. If windings, additional diodes and the regulator of tension of the generator are serviceable, and in gates there is no short circuit, then the break in gates is the reason of reduction of the given current.

Check of additional diodes

Fig. 7.11. The scheme for check of additional diodes: 1 – generator; 2 – control lamp; 3 – rechargeable battery

Short circuit of additional diodes can be checked without removal and dismantling of the generator according to the scheme provided on fig. 7.11. As well as for check of gates of the vypryamitelny block, at the same time it is necessary to disconnect wires from the rechargeable battery and the generator, to remove the protection cover of the generator and to disconnect a wire from a conclusion of "D+" of the regulator of tension.
"Plus" attach batteries through a lamp (1–3 W, 12 V) to a conclusion of the "D" generator, and "minus" to one of phase conclusions of a winding of the stator.
If the lamp lights up, then in some of additional diodes there is a short circuit. It is possible to find the damaged diode only having removed the vypryamitelny block and checking each diode separately.
The break in additional diodes can be found an oscillograph on distortion of a curve of tension on the plug "D", and also on the low voltage (it is lower than 14 V) on the plug "D" with an average frequency of rotation of a rotor of the generator.

Check of the regulator of tension
Operation of the regulator of tension consists in continuous and automatic change of current of excitement of the generator so that tension of the generator was supported in the set limits at change of frequency of rotation and current of loading of the generator.
Check on the car
For check it is necessary to have the voltmeter of a direct current with a scale till 15-30 in an accuracy class not worse 1,0.
After 15 min. operation of the engine on average turns at the included headlights measure tension between the In + plug and mass of the generator. Tension has to be in limits of 13,2-14,7 Century.
In case it is observed systematic недозаряд or the recharge of the rechargeable battery and adjustable tension does not keep within the specified limits, the regulator of tension needs to be replaced.
Check of the removed regulator

Fig. 7.12. The scheme for check of the regulator of tension: 1 – control lamp; 2 – conclusion to "mass" of the regulator of tension; 3 – conclusion of "DF" of the regulator of tension; 4 – tension regulator; 5 – conclusion of "D+" of the regulator of tension; And — to the power supply

The regulator assembled with the brush holder removed from the generator is checked according to the scheme provided on fig. 7.12.
Between brushes include a lamp of 1-3 W, 12 V. K to conclusions of D + and "mass" of the regulator attach the power supply at first of 12 in, and then of 15-16 V.
If the regulator is serviceable, then in the first case the lamp has to burn, and in the second — to die away.
If the lamp burns in both cases, then in the regulator breakdown and if does not burn in both cases, then or in the regulator is available break, or not contact between brushes and conclusions of the regulator of tension. The last can be checked, attaching wires from a lamp not to brushes, and directly to conclusions of D + and tension DF regulator.

Check of the condenser
The condenser serves for protection of the electronic equipment of the car against tension impulses in system of ignition, and also for decrease in hindrances to radio reception.
Damage of the condenser or weakening of its fastening on the generator (deterioration in contact with weight) is found on increase in hindrances to radio reception at the working engine.
Approximately serviceability of the condenser can be checked the megohm meter or a tester (on a scale of 1-10 megohms). If in the condenser there is no break, then at the time of connection of probes of the device to conclusions of the condenser of the shooter has to deviate towards reduction of resistance, and then return gradually back.
The condenser capacity measured by the special device has to be 2,2 мкФ ±20%.