Dings Magnetic Group Stationary Electro Overhead Magnets - Manual (Page 13)

Revised January 19, 2011
STEP 5
Turn off and lock-out the power to the rectifier. Disconnect the two leads from the rectifier to
the magnet at the magnet box terminals, using caution not to rotate the studs in the feed
through terminals as the internal connections may be damaged. The magnet must be cold for
the following tests. Using the watts and the volts from the nameplate on the magnet, square
the nameplate DC volts (115 VDC or 230 VDC) and divide by the nameplate watts to get the
target ohm reading. Measure the ohms between the two magnet box terminals.
VOLTS:
NOTE: There is no polarity for the magnet terminal posts. Either lead can be connected to
either terminal.
If the ohm reading is within + 10% of the target ohm reading, go to Step 6. If the ohm reading
is out of tolerance or infinity, consult the factory, supplying all of the above readings that were
taken.
STEP 6
Measure the ohm reading between one of the magnet box terminals and the magnet housing,
(The preferred measuring instrument is a megger.)
OHMS:
If the reading is one megohm (1,000,000 ohms) or larger, the magnet is OK. If the megger
ohm reading is out of tolerance, consult the factory, supplying all of the above readings that
were taken.
If it has been determined that the rectifier and the magnetic separator are electrically sound
and the performance of the separator is still in doubt, contact the factory for further assistance.
There are many factors which can affect the ability of a separator to attract metal.
SIGNIFICANCE OF ELECTRICAL READINGS:
Low DC Volts Magnet will be weak
Low Ohms (resistance) Possible shorted turns in coils
High Ohms Possible poor connection or open coil circuit
Low DC Amps Possible poor connection or open coil circuit
High DC Amps Possible shorted turns in coils
Megger Reading Less One or more coils are grounded, poor insulation or
Than 1 Megohm transformer oil is contaminated with water
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