Baker D30R, Руководство пользователя

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Surge Test Applications
12/3/2009 | 71-022 V6
D30R 55
are alike, this is an indication that the motor is good. If anything other than good patterns is
seen, there is a possible fault.
Two or more single coils
Surge testing can be used to test two or more identical single coils separately and then
compare their wave patterns against each other.
Note : Use Quick Store for a fast determination of the results of the test.
If the wave patterns are stable and superimpose on the display, the two windings are
identical, have no faults and the insulation in both coils is good.
Notices for two single coils
−
All windings or magnetic material (iron or ferrite) close to the coils under test must be
the same for both coils. For example, if DC fields coils are being tested, both should have
the pole pieces inserted or both removed. A coil on a table when compared to an
identical coil in the frame will show separation of the wave patterns because inductance
differs in iron and air.
−
Slight variations in magnetics of the tested device can result in similar coils not
comparing identically. An example of this is synchronous pole pieces, one of which is
making better magnetic contact with the rotor then the comparing pole. For this reason
it is recommended that devices like pole pieces be evaluated individually and not
compared.
−
Paschen’s Law states that a voltage greater than 334 V is required to initiate an arc
between two conductors in air. This would suggest a minimum voltage for surge testing
to be greater than 334 V. Because of the sometimes non-linear distribution of the surge
pulse, it is recommended that a minimum surge potential of 500 V be used when testing
a two terminal device.
−
Shunt coils often have a small error in turns count. Some mismatch or separation of
patterns should be acceptable. If the wave patterns are very close in shape and remain
stable during the test, the coils generally are acceptable. In addition, winding tolerances
on single coils may allow for differences in turns count, which causes a slight, steady
separation. The operator should investigate whether this condition is acceptable or not.
−
A slight imbalance (separation) may be noticed if the windings are not correctly phased:
i.e.: the winding configuration of one compared to another is clockwise verses
counterclockwise. Try reversing one set of test leads connections and repeating the test
before rejecting the winding.
−
Many two terminal devices have very high turns count. The waveform displayed is similar
to that of an open circuit. In this case, the impedance of the coil is too high to be tested.
Double check for poor connections and test lead breakage to see if these conditions may
be causing the apparent open condition.
Wound rotor motors
Wound rotor motors are tested as though they are two separate three phase windings where
one is the stator and the other is the rotor. Before testing wound rotor motors remember to
remove the brushes touching the slip rings and short together the slip rings with jumpers.
The jumpers minimize the coupling effect between rotor and stator.
Since the rotor is shorted out there will be no chance for a high induced voltage transformed
from the stator to damage the rotor.
Note : Check the motor name plate for rotor voltage to calculate the rotor test voltage level.
Rotor voltage is not the same as the stator voltage.
If the wave patterns are stable and they superimpose on the display, the windings are
identical, have no faults and the insulation of both coils is good.