ECA-443-1979.pdf
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1、E I A/NAR M STANDARD FOR SOLID STATE RELAYS ANSI/E IA RS443-1979 Approved April 6, 1978 EIA STANDARD RS.443 APRIL 1979 5 h Engineering Department ELECTRONIC INDUSTRIES ASSOCIATION Copyright Electronic Components, Assemblies here the load voltage will not be at zero magnitude when the relay goes out
2、of conduction, At turn-off, a voltage equal in magnitude to the load voltage instantaneously appears across the output terminals of the relay. The conditions for a commutating dV/dt failure now exist: 1 . 2. The thyristor was previously carrying current. At turn-off, a rapid rate of ris6 of voltage
3、appeared across the thyristor. This mode of failure is much more serious than a static dV/dt failure. With the static failure, the false conduction will be for a maximum of one-half line cycle. When the first commutating failure occurs, it is Copyright Electronic Components, Assemblies & Materials A
4、ssociation Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 00:25:56 MDTNo reproduction or networking permitted without license from IHS -,-,- r- EIA 443 79 W 323YbOO 0068912 9 RS-443 Page 63 likely that another &ill occur at the
5、next turn-off. It then- can be seen that once a commutating dV/dt failure occurs, the device may never turn off. The relay will be able to withstand much higher values of dV/dt in the static mode than in the commutating mode of operation. The relay will become more prone to dV/dt failures as the thy
6、ristors jmction temperature increases. Also, the relay becomes more prone to commutating dV/dt failures as the load current is increased. The classic method of protecting a relay against dV/dt failures is to place a snubber filter across the output terminals of the relays. This filter consists of a
7、series combination of a resistor and a capacitor. Typically, the value of the capacitor is .22uF or less, and the resistor i s 100 ohms or less. Some manufacturers place a filter inside of the relay case. Should the potential for 8 problem in this area exist, the manufacturer should be consulted. 14
8、.8.4 Input Characteristics Normally, the input drive is applied as a step function. The input may be ramped, but this could cause some effects in the output switching which are undesirable. Q Primarily, there may not, be full cycle conduction. Instead, the thyristor may fire when the load voltage is
9、 one polarity and may not fire when the load voltage has the opposite polarity. This effect will only be present until the input is sufficient in magnitude to fully turn the output on. This is sometimes referred to as a half-cycle condition. The time required for the relay to turn on or off may also
10、 be a function of the input drive level. Some relays have a filter in the input. The response time of the filter on operate is a function of the input drive level. Also, the response of the filter on turn-off will be a function of the drive level. I Copyright Electronic Components, Assemblies & Mate
11、rials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/29/2007 00:25:56 MDTNo reproduction or networking permitted without license from IHS -,-,- E I A 443 79 m 3234600 00b89l13 O m 3 i RS-463 1 Page64. With hybrid solid state
12、 relays, units where the input is a mechanical relay, the operate time of the relay is a function of its overdrive. Depending on the amount of overdrive, the operate time of the relay will vary over several hundred microseconds. Since most hybrid relays are random turn on devices, this variable oper
13、ate time will be directly reflected to the operate time of he solid state relay. O 14.8.5 Input Transient Effects All thyristors can turn on in a few microseconds after being gated. There is, however, some delay between the time the input is driven and gating occurs. This delay can be anywhere from
14、a few microseconds to several hundred milliseconds. The delay time is a function of the relays internal interface circuitry. It follows that a relay can false-fire on a few microseconds of input if the total response time of the relay is equal to or less than the duration of the noise burst. With Ze
15、ro Voltage Turn On Relays, the noise burst must occur in that brief period when the zero voltage drive network was enabled. It is proper to say that this type of relay is statistically less susceptible to input noise than a random turn-on relay. 6 14.8.6 Input Polarity Many solid state relays have a
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