3-22. FIELD SHUNT CONTACTOR (cont)
Measure final pressure as follows:
(1) Block the armature in the
(2) Measure the pull required to
just separate the contact tips.
(3) Check for a pull of 5 to 8 lb
(2.267 to 3.628 kg).
c. If the pressure measurements are not correct, check for the following conditions:
Low initial pressure - defective contact pressure spring, worn spring seat or washers, or worn stop.
Low final pressure - defective pressure spring, low wear allowance, or badly worn tips.
32. Measure and adjust coil operating current as follows:
Use multimeter and measure resistance of coil. The indicator shall be between 34.65 and 42.35 ohms.
Replace defective coil.
b. Connect power supply and a
mmeter to coil.
Apply current and increase slowly until contactor picks up. Check that the contactor picks up without
hesitation, that is, in one quick motion including the contact wipe. The current measured shall be 0.436 to
d. Adjust calibrating screw until proper value of current is indicated.
33. Manually operate interlock contacts. Use a multimeter and check resistance of contacts for infinity while open and
continuity while closed.