S7-300的模塊機架（起物理支撐作用，無背板總線），西門子提供五種規格的導軌。
電源模塊（PS）
將市電電壓（AC120/230V）轉換為DC24V，為CPU和24V直流負載電路（信號模塊、傳感器、執行器等）提供直流電源。輸出電流有2A、5A、10A三種
正常：綠色LED燈亮
過載：綠色LED燈閃
短路：綠色LED燈暗（電壓跌落，短路消失后自動恢復）

339021AA
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339306CA7
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339420AX
3SE21000E
3SE21001B
3SE21001C
3SE21001D
3SE21001DV000AH3

671532BA020XB4
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671532BA810XB0
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671560AA010XA0
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671570AF810XA0
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671580AA010XA0
671580AD000XA0
671580AD010XA0
671583AD000XA0
671583AD010XA0
671740AA100AA0
67178H000AE0

3RV10111GA20
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3RV10111HA15
3RV10111HA20
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3RV10111KA10
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3RV10111KA20
3RV10210AA10
3RV10210AA15
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3RV10210CA10
3RV10210CA15
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3RV10210DA15
3RV10210EA10
3RV10210EA15
3RV10210FA10
3RV10210FA15
3RV10210GA10
3RV10210GA15
3RV10210HA10
3RV10210HA15
3RV10210JA10
3RV10210JA15
3RV10210KA10
3RV10210KA15
3RV10211AA10
3RV10211AA15
3RV10211BA10
3RV10211BA15
3RV10211CA10