Installation, Operation and Service Manual LKP Series
© 2020 DynAmp, LLC Page 18
041736 N
A.) The dc voltage range may be as high as 75 Vdc (see “D” below). Make certain the
voltmeter being used is set to measure average dc volts in this range.
B.) The measured bus and all other high current buses in the vicinity (or in the facility,
within 10-20 meters away) should be operating at or near their highest levels.
Note: All magnetic field sources will affect the channel voltage readings.
C.) Make a photocopy of a table “Form for Recording Channel Voltage Measurements”.,
depending on the model. The initial readings are made as instructed on the form, and
are recorded in the individual blocks, which graphically show channel locations on the
Measuring Head.
D.) Excluding the effects of external magnetic sources and assuming a full rated bus
current, each channel is expected (by calculation) to measure approximately 18 V to 30
Vdc. In practice, channel readings should be more on the order of 10 V to 30 Vdc, but
that may not be achievable. A channel failure will usually be indicated by either a full-
off (near zero), half-on (35-38 V) or full-on (70-75 V) condition.
Avoid operating the unit for an extended time with any channel output over 40 V.
This will permanently damage the system. For voltages over 40 V, consult the
E.) If any of the channel readings do indicate trouble, refer to Theory of Operations and
Maintenance & Spare Parts sections and resolve the problem; then proceed with
"Magnetic Centering".
Note 1. Low Readings: A very low amplifier output voltage may be normal for certain
channels; however, ripple can be as high as 3 V on a non-operating (full-off) channel.
Thus, a very low reading (i.e., 2 V to 5 V, should be suspected as a possible problem;
subsequent Measuring Head movement or other magnetic change may show that the
channel is good. A blown channel fuse can cause a low reading.
Note 2. High Readings: The maximum allowable channel output of 40 V relates to the
maximum heat dissipation that the channel can safely handle. A reading of 30 V to 40 V
makes a change in Measuring Head position highly desirable. A reading exceeding 40 V
makes a Measuring Head position change necessary. A reading of 70-75 V indicates a
full-on channel condition or a blown channel fuse, and requires immediate action to resolve
the problem. A reading of 35-38 V when immediately adjacent channels are significantly
different may indicate that one of the two SCRs in the channel has failed.
4.10 MAGNETIC CENTERING
The distribution of load, or heat, among all channels will be optimized by magnetic
centering of the Measuring Head relative to both the bus and the total magnetic
environment of the Measuring Head. In general, this simply means moving the Measuring
Head so that channels with high voltage readings will be farther from the bus, and channels
with low readings will be nearer the bus. Whether or not the Measuring Head should
actually be moved depends on three factors:
A.) The possible impracticality or difficulty of moving the Measuring Head because of
support-system requirements, clearances available, etc.
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