TM 5-688
CHAPTER 1
INTRODUCTION
1-2. Scope.
1-1. Purpose.
This manual identifies the classes of electrical equip-
This manual provides guidance required to identify
ment that are sensitive to frequency and voltage varia-
the voltage and frequency standards of various for-
tions. Appendix B covers identification of various low
eign countries for both medium and low voltage sys-
and medium voltage levels, along with the system fre-
tems. It also identifies the classes of equipment that
quencies, used by countries around the world. Derating
are sensitive to voltage and frequency differences.
factors are discussed and developed for the six gener-
Foreign countries around the world use different
ic types of equipment in chapter 3. Appendix C sum-
electrical standards for voltage and frequency than
marizes the derating factors presented in chapter 3 for
those of the United States. Some electrical equip-
different voltage and frequency environments.
ment will operate properly at an electrical frequency
of either 50 or 60 Hz. Equipment designed for 60
Hz that will not operate properly at 50 Hz is termed
1-3. References.
"50 Hz sensitive," and equipment designed for 50
Appendix A contains a list of publications referenced in
Hz that will not operate properly at 60 Hz is termed
this manual.
"60 Hz sensitive."
1-1
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