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U.P.S. System Key Interlock

Printable Technical Information System No. 1
Printable Technical Information System No. 2

Uninterrupted power source scheme 1: To insure the proper sequential operation of UPS related equipment.

Initial Condition: The critical load is fed through the UPS through the UPS output breaker. The Solenoid Key Release Unit (SKRU) has its respective interlock key "A" captive with its internal form C contacts in position A. The maintenance bypass breaker is locked open with no "A" key present while the "B" key is captive. The UPS output breaker is closed with no "B" key present while the "A" key is captive.

Switching Scenario: Supply of the critical load through the UPS maintenance bypass breaker: The UPS is placed in the bypass mode. Upon completion a signal is sent to the SKRU enabling release of the "A" key while placing the internal form C contacts into position B. Use the "A" key to unlock and close the maintenance bypass breaker thereby trapping the "A" key and releasing the "B" key. Open and lock the UPS output breaker using the "B" key which will trap the "B" key and release the "A" key. Re-insert and "A" key in the SKRU and turn, thereby trapping key A and returning the form C contacts to position A. Reverse to restore the initial condition.

Uninterrupted power source scheme 2: To insure the proper sequential operation of UPS related equipment.

Initial Condition: The critical load is fed through the UPS through the UPS output breaker. The Solenoid Key Release Unit (SKRU) has its respective interlock key "A" captive with its internal form C contacts in position A. The maintenance bypass breaker is locked open with no key present. The UPS output breaker is closed with the "B"key captive.

Switching Scenario: Supply of the critical load through the UPS maintenance bypass breaker: The UPS is placed in the bypass mode. Upon completion a signal is sent to the SKRU enabling release of the "A" key while placing the internal form C contacts into position B. Use the "A" key to unlock and close the maintenance bypass breaker. Open and lock the UPS output breaker thereby releasing the "B" key. Insert the "B" key in the SKRU and turn, thereby trapping key "B" and returning the form C contacts to position A. Reverse to restore the initial condition.

Note: The SKRU is a dual combinated interlock and can accept either an "A" or a "B" key.

Additional Schemes:
A / A1 / B / B1 / C / D / E / F / G / H / H1 / H2 / K / L / M / N / O / P / R / U.P.S. System / Capacitor Bank Access Scheme