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Elmo Compliance with MIL-STD-1275B
February 2007- Ver. 1.0
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Elmo Compliance with MIL-STD-1275B
CHARACTERISTICS OF 28 VOLT DC ELECTRICAL SYSTEMS IN MILITARY VEHICLES
Operating in "battery-powered" applications (with or without an alternator or generator) exposes the electrical equipment to severe electrical interferences such as: * surges * spikes * transients * EMI * over voltage * under voltage * voltage ripple * reverse polarity Harsh "battery-powered" environment interferences are unique in nature and have very high energy and long durations. As a result, the "battery-powered" interferences are unable to be managed, resolved or prevented by conventional remedies such as MOVs (metal oxide varistors), tranzorbers, zener and avalanche diodes, passive filters, capacitors, fuses, circuit breakers, etc. which are used to protect electronic equipment. The MIL-STD-1275B sets the requirements that all 24VDC "battery-powered" equipment must be compliant in order to ensure reliable and fault free operation. Although complying with the MIL-STD-1275B is mandatory in military applications, it is highly recommended to be adopted in any type of "battery-powered" equipment. The MIL-STD-1275B addresses 3 major interferences: 1. Surge-40V 2. Surge-100V 3. Spike-250V
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Elmo Compliance with MIL-STD-1275B
Surge-40V Electrical System Requirement Equipment shall continue to operate normally throughout these tests without damage to any components
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Surge 40V
LOCI of SURGES in a FAULT-FREE ELECTRICAL SYSTEM MIL-STD-1275B
40 35
Source Impedance approx. 20 milliohms
P EA K V OL T A GE
30 25 20 18 15 10
1ms
10ms
50ms
100 ms
500ms
1.0 s
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Elmo Compliance with MIL-STD-1275B
Surge-100V Electrical System Requirement Equipment shall function as specified
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Surge 100V
LOCI of SURGES in a TYPICAL DC ELECTRICAL SYSTEM
100 90 80 70
MIL-STD-1275B
Source Impedance approx. 500 milliohms
V OLTAGE
Total Surge Energy in a DC Electrical System approx. 1000 Joules for a Single Surge Event!
60 50 40 30 20 10
1ms
10ms
50ms
100ms
1000ms
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Elmo Compliance with MIL-STD-1275B
Spike-250V 3 Spike 250V Electrical System Requirement The voltage spikes so imposed shall not cause any damage nor effect the normal operation of the equipment
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Elmo Compliance with MIL-STD-1275B
Elmo ExtrIQ products are designated by: * XXX-YY/48 * XXX-YY/60 * XXX-YY/100 * XXX-YY/200 They comply with the requirements to withstand the 3 types of interferences as defined by the MIL-STD-1275B described above.
Surge-100V
Special attention must be paid to the Surge 100V interference. The MIL-STD-1275B requires that the electrical equipment "...shall function as specified" by suppliers. Under the conditions of Surge 100V, Elmo's products will be disabled by over voltage protection (except for the XXX-YY/200 models which will operate normally at 100VDC). This condition suits most (if not all) applications. There is no point in trying to keep the servo driver enabled when a 500 milliohm resistor (interference condition) "exists" in series to the 24V battery power supply (for example: the drop on this resistance when peaking 100A is 50V). The servo system will hardly operate as the voltage drop on the 0.5 ohm resistor will be too high. It is a rare condition when "the equipment shall continue to operate normally throughout..." the "Surge 100V" is required. Elmo proposes some "remedies" which are listed below for such cases: * The simplest way is to use a drive that can operate "normally" at 100V. Usually those drives are designated as XXX-YY/200. In many cases it will be impractical because higher voltage rating servo drives are usually rated for lower currents and are significantly less efficient than the lower voltages drives. o In extreme cases, Elmo will be able to modify the XXX-YY/100 to operate "normally" at Surge-100V. * The only way to keep the servo system enabled and "operating normally" during the Surge 100V with high current low voltage drives is by adding an enormous stack of capacitors to serve as the energy/voltage reservoir during the interference. In most cases, it is impractical and not required by the application. * In low current applications (<20A), it could be practical to add a simple electrical circuit that will limit the maximum voltage applied to the servo drive during the Surge 100V to the "normal operating conditions".
Surge 100V Summary
Elmo was and is involved in many projects that meet the MIL-STD-1275 (A or B). In only one case, there was a request to "continue normal operation" during Surge 100V.
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