Bench Testing - Instructions; Cut-Out Relay Check - Fiat 411 R Service Manual

cause Spark welding of the contacts. it is therefore absolutely necessary to connect terminals bearing
the same number, keeping in mind that even if the wrong connections are corrected and the operation be-
comes normal again, the useful life has been nonetheless shortened.
3. - The control box should never undergo shocks of any kind, particularly the lower side which houses
the resistances (Fig. 159).
During bench testing the box must be positioned with the terminals downwards, and with an insulator
lining between the bench mounting and the base.
4. - The grounding connection between the control box and the tractor must be secure, otherwise there
will be no regulation there being no current going across the shunt windings. In this case the generator
voltage output which increases with speed (es it is not regulated). will burn the winding ends and dete-
riorate the voltage and current regulator contacts clue to the excess of current across the field winding
of the generator.
Bench testing ~ Instructions.
To check the performance of the control box rnod. GP1;'24,l7 start with the following operations without
unseallng the unit:
— piece on the bench e generator model DQ113124,/'i_l3 (regardless oi modification 5%., E, etc.};
- connect the generator to an electric motor the speed of which can undergo tine variations over a wide
range and provide a 30 V battery;
— make ready the instruments end gauges necessary to the elements oi the control box keeping in mind
that dependable results are dependent upon the observance of the ruies and procedure which will
be given below.
Caution: The test must absolutely be performed at the temperature specified for each control and after
at least 30 minute operation i. e., when the temperature condition specified has been reached.
This requires a special oven suitable for the thermal stabilization of the control boxes. Tests performed
otherwise will not give dependable results.
a} Contact closing voltage at 25°i'I0°C (77@;j;
gt; 50° F) ambient temperature.
Cut-—out relay check.
in suri-oundlngs with the temperature specified above
connect the control box according to the wiring
diagram of Fig. 154 and run if idle at 30 V for T5
3| |;. to 18 minutes.
5! E? 30
This preliminary operation allows the unit to reach
the thermal level allowing the cut-out shunt wino'fog
and the bimetallic spring blade to reach thermal
stability after en initial period during which the
voltage oscillates considerably,
5: 5?
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Kit/'""" "
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Fig- 154» Electrical diagram of the arrengementforiesting
the ':"t'°"t 'Bi*'1Y Contact closing temperature.
M. Test bench electric motor - cs. Generator DC l15;'24f7_/3
and its medlfied versions ~ V. Voitmeter, 39 V top reading.
100
lmmecfialfely after obtaining thermal siab1'lity, star-
ting from an inactive generator, gradually increase
the speed to check the voltmeter for the value of
the cut~out contact closing voltage, which should
real:-' 25.1 to 25.9 V when the light goes on.
la) Reverse current (in ambient temperature of
25°i10° C = ?7°i 50° F}.
This test soufd be performed immediately after the
contact closing voltage tesi, in order to keep the
thermal stability reached in the preceding test.
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