Baker D30R, User'S Manual & Operating Instructions

Page: 90 / 142

D30R Users Manual
90
Do Not Touch Test Leads while test is in Progress!
71-023 Rev C 5/8/2007
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 volts 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 volts.
Because of the sometimes non-linear distribution of the surge pulse, it
is recommended that a minimum surge potential of 500 volts 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: ie: 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. Procedures to
successfully test the wound rotor motor are as follows.
1. Remove the brushes touching the slip rings.
2.
Short together the slip rings with jumpers. The jumpers minimize the
coupling effect between rotor and stator.