Eaton Power Circuit Breaker MDN-512

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.

When a circuit breaker experiences a high-level fault or during regularly scheduled maintenance periods, the circuit breaker’s arc chutes and arc chambers should be inspected for any kind of damage or dirt. Be especially alert for signs of significant erosion of the V-shaped plated inside the arc chute.

Arc chutes fit inside the arc chambers and down over the primary contacts. Each arc chute is held in place by either 1 (SB) or 4 (SBSE) top inserted screws.

Remove arc chute screws and all arc chutes from the arc chamber.

Turn each arc chute upside down and visually inspect the inside.

Look for erosion and sooty discoloration on the splitter plates and insulating jacket If arc chutes show severe signs of erosion or discoloration, replace with a new arc chute.

Note: Because the arc chutes are removed, this is an ideal time to inspect the primary contacts for wear (See Primary Contact Inspection procedure on page 59).

When the inspections are complete, position each arc chute over its respective set of primary contacts, and secure in place with the screw(s) removed earlier Be sure to torque arc chute screws to 35 to 45 in-lb.

Sign off on the arc chute inspection

Charge the breaker mechanism springs either using the charging handle or the motor operator.

Press the ON pushbutton to close the breaker manually and verify closing by noting the state of the indicating flag.

Charge the breaker mechanism springs either using the charging handle or the motor operator. If using the motor operator, disconnect power to it to prevent automatic recharging.

Press the OFF pushbutton to manually open the breaker.

Press the ON pushbutton to manually close the breaker. Is the breaker closed?

Press the OFF pushbutton to manually open the breaker. Is the breaker open?

Note: Repeat this entire described test procedure three times.

Sign off on the manual operation functional testing

Note: 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.

1. Charge the breaker mechanism springs using the motor operator, then if equipped with a UVR, energize the UVR with the rated voltage.

2. Close the breaker by applying rated voltage to the spring release accessory and verify closing by noting the state of the indicating flag.

3. Charge the breaker mechanism springs using the motor operator If using the motor operator, after charging, remove power to the motor operator to prevent automatic recharging.

4. Open the breaker by applying rated voltage to the shunt trip accessory.

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

5. With UVR energized, close the breaker using the spring release accessory The breaker should now be closed.

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 with PPE!

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