Eaton Power Circuit Breaker MDS-408

Warning: Breaker accessory voltages can vary within the same breaker. Be sure to review the accessory voltage rating before energizing as damage may occur.

This test procedure assumes that the breaker is equipped with optional shunt trip (ST), undervoltage release (UVR), and/or spring release (SR) accessories (Figure 94). If one accessory is missing, substitute the manual button or manual charge handle to replace the accessory’s function. If equipped with a motor operator, the voltage is listed on the breaker nameplate.

Enter the voltage of the motor operator

Did the breaker mechanism springs charge using the motor operator?

Did the breaker close by applying rated voltage to the spring release accessory?

Did the breaker mechanism springs charge using the motor operator?

Did the breaker open by applying rated voltage to the shunt trip accessory?

Note: If UVR is not installed, proceed to step 7.

With UVR energized, did the breaker close using the spring release accessory?

Pre-inspection conditions: Device (Fixed): Position of Poles: Open, Mechanism: Discharged, Device Position in Cassette: -. Device (Drawout): Position of Poles: Open, Mechanism: Discharged, Device Position in Cassette: Removed.

Note: Using the mating line of the housing halves as a reference guide will assist in this visual inspection.

Remove the arc chutes, look directly down into the arc chamber (Figure 98), and visually inspect each primary contact structure for signs of wear and/or damage.

Use the contact wear indicator to inspect each contact The contact wear indicator is the relative position of the individual contact fingers to a narrow, side-to-side ledge inside the arc chamber The ledge is actually part of the arc chamber When the circuit breaker is closed and the contacts are in good condition, the narrow ledge is covered by the back end of each of the contact fingers (Figure 99) If the back end of any of the contacts are below the ledge, the contact assembly should be replaced.

Once the inspection is complete, be sure to verify the arc chutes are properly replaced as previously described in the Arc Chute Inspection procedure.

WARNING: ARC CHUTES MUST BE SECURED PROPERLY IN PLACE BEFORE A CIRCUIT BREAKER IS INSTALLED IN A CIRCUIT BREAKER COMPARTMENT. FAILURE TO DO THIS COULD RESULT IN EQUIPMENT DAMAGE, BODILY INJURY, OR EVEN DEATH.

Device (Fixed): Position of Poles: Open, Mechanism: Discharged, Device Position in Cassette: -.

Device (Drawout): Position of Poles: Open, Mechanism: Discharged, Device Position in Cassette: Removed.

2. With breaker removed from cell, verify that the breaker secondary disconnect pins are fully seated and locked into position by lightly pulling on each wire individually.

Note: Do not exceed 1 lb of force or damage to pin or housing may occur.

3. Ensure all pins are straight without bends, corrosion, or show evidence of arcing.

Warning: This procedure requires trained personnel!

Charged the breaker mechanism springs using the charging handle or the motor operator

Closed the breaker by applying rated voltage to the spring release accessory and verified closing by noting the state of the indicating flag

Charged the breaker mechanism springs again using the charging handle or the motor operator

Checked the state of the pop-out trip indicator and reset it if it was 'out'

Pressed the ON pushbutton to manually close the breaker and reset the indicator if it was 'out'

Used the Functional Test Kit to trip the breaker by setting its SELECT TEST switch to INST, then pressing its PUSH TO TEST button

Verified that the trip indicator pop-out button is 'out' and then reset it by pressing the pop-out button

Reset the trip unit by the Reset/Battery Test pushbutton on the front of the trip unit

Device (Fixed): Position of Poles

Device (Fixed): Device Position in Cassette

Device (Drawout): Position of Poles

Device (Drawout): Device Position in Cassette

Inspect the breaker for nicked wires, cracks in plastic parts, and loose screws