MIL-STD-704F
4.2.3 Power failure. The loss of power (AC or DC) or the loss of one or more phases of AC power to any utilization equipment terminal shall not result in an unsafe condition or damage to utilization equipment.
4.2.4 AC power utilization. Utilization equipment that requires more than 0.5 kVA of AC power shall be configured to utilize three-phase steady state balanced power. Load unbalance of individual utilization equipment shall be within the limits of figure 1. The load unbalance of utilization equipment whose total load is greater than 30 kVA shall be no greater than 3.33 percent of its total three-phase load. Single-phase AC power shall be used only on a line-to-neutral basis. AC power shall not be half-wave rectified.
4.3 External power source requirement. External electric power sources shall supply power having the characteristics specified in this standard at the power input terminals of the aircraft electric utilization equipment. In order to allow for steady state voltage drop between the aircraft external power receptacle and the aircraft utilization equipment terminals, the voltage at the external power receptacle shall be as follows:
a. AC system 113 to 118 volts (AC voltage drop of 0 to 5 volts) b. 28 VDC system 24 to 29 volts (DC voltage drop of 0 to 2 volts) c. 270 VDC system 260 to 280 volts (DC voltage drop of 0 to 10 volts)
4.4 Test requirements. Equipment testing is required to demonstrate utilization equipment compatibility with the electric power characteristics of this standard. Utilization equipment test requirements shall be in accordance with the equipment detail specification. The applicable test methods of MIL-HDBK-704 shall be used to determine that the utilization equipment complies with this standard. Aircraft shall be tested to demonstrate that the aircraft electric system power characteristics are within the limits of this standard throughout all operating conditions of the aircraft and its utilization equipment. Aircraft test requirements shall be in accordance with the aircraft detail specification.
5. DETAILED REQUIREMENTS
5.1 Transfer operation characteristics. Under conditions of bus or power source transfers, voltage and frequency shall not vary between zero and normal operating limits for longer than 50 milliseconds. A normal transient may occur upon completion of a transfer.
5.2 AC power characteristics.
5.2.1 Type system. AC systems shall provide electrical power using single-phase or three-phase wire-connected grounded neutral systems. The voltage waveform shall be a sine wave with a nominal voltage of 115/200 volts and a nominal frequency of 400 Hz. Variable frequency and double-voltage systems may be used as alternative electrical power systems. Variable frequency systems have frequencies varying from 360 to 800 Hz with a nominal voltage of 115/200 volts. Double-voltage systems have nominal voltages of 230/400 volts and a nominal frequency of 400 Hz. A third alternative for secondary electric power systems is single-phase 60
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