Testing Procedures for Power Engineering - Revision history

Doduco Admin: /* Testing According to UL and CSA */

2023-01-09T11:56:25Z

‎Testing According to UL and CSA

Doduco Admin: /* Switching Capacity */

2023-01-09T11:54:33Z

‎Switching Capacity

Doduco Admin: /* Analysis of the Switching Sequence */

2023-01-09T11:52:05Z

‎Analysis of the Switching Sequence

Doduco Admin: /* Analysis of the Switching Sequence */

2023-01-09T11:51:18Z

‎Analysis of the Switching Sequence

Doduco Admin: /* Temperature Rise */

2023-01-09T11:46:40Z

‎Temperature Rise

Doduco Admin: /* Switching Capacity */

2023-01-09T11:45:40Z

‎Switching Capacity

Doduco Admin: /* Testing According to IEC/EN */

2023-01-09T11:44:45Z

‎Testing According to IEC/EN

Doduco Admin: /* Testing According to IEC/EN */

2023-01-09T11:42:55Z

‎Testing According to IEC/EN

Doduco Admin: /* Testing According to IEC/EN */

2023-01-09T11:41:03Z

‎Testing According to IEC/EN

Doduco Admin: /* Temperature Rise */

2023-01-09T11:40:07Z

‎Temperature Rise

@@ Line 316: / Line 316: @@
 ===<!--13.4.3-->Testing According to UL and CSA===
-The test standards for North America according to UL (USA) and CSA (Canada) differ in part substantially from those of the IEC and harmonized European EN standards. In the US and Canada the standards differentiate between switchgear for power distribution, for example low voltage circuit breakers and power switches covered by UL 489 (UL = Underwriters Laboratories) and CSAC22.2 No. 5-02 (CSA = Canadian Standard Association) and those for industrial switching devices, for example contactors covered by UL 508 and CSA-C22.2 No. 14 respectively. For industrial controls contactors and other switching devices are often classified in the USA according to NEMA (National Electrical Manufacturers Association) current rating. North American standards emphasize the prevention of fires and therefore have high limit requirements on temperature rise. They also require larger air and creep gaps than those of IEC, which leads to significant differences in the design of the switches and their contact systems.
+The test standards for North America according to UL (USA) and CSA (Canada) differ in part substantially from those of the IEC and harmonized European EN standards. In the US and Canada the standards differentiate between switchgear for power distribution, for example low voltage circuit breakers and power switches covered by UL 489 (UL = Underwriters Laboratories) and CSAC22.2 No. 5-02 (CSA = Canadian Standard Association) and those for industrial switching devices, for example contactors covered by UL 508 and CSA-C22.2 No. 14 respectively. For industrial controls, contactors and other switching devices are often classified in the USA according to NEMA (National Electrical Manufacturers Association) current rating. North American standards emphasize the prevention of fires and therefore has high limit requirements on temperature rise. They also require larger air and creep gaps than those of IEC, which leads to significant differences in the design of the switches and their contact systems.
 ==References==

@@ Line 243: / Line 243: @@
 ====<!--13.4.2.4-->Switching Capacity====
-The main requirement for low voltage power switches is the withstanding of high short circuit currents. The short circuit switching capacity of power switches is determined in tests according to IEC/EN 60947-2 <xr id="tab:Testing for the Short Circuit Breaking Capacity of Low Voltage Power Switches According to IECEN 60947-2 (Shortened Summary)"/><!--(Tab. 13.3)-->. These test differentiate between the maximum short circuit current switching capacity (ultimate current limit) I<sub>CU</sub> and the operational (or service) short circuit current capacity I<sub>CS</sub> .
+The main requirement for low voltage power switches is the withstanding of high short circuit currents. The short circuit switching capacity of power switches is determined in tests according to IEC/EN 60947-2 (<xr id="tab:Testing for the Short Circuit Breaking Capacity of Low Voltage Power Switches According to IECEN 60947-2 (Shortened Summary)"/><!--(Tab. 13.3)-->). These tests differentiate between the maximum short circuit current switching capacity (ultimate current limit) I<sub>CU</sub> and the operational (or service) short circuit current capacity I<sub>CS</sub> .
 When specifying I<sub>CU</sub> it must be guaranteed that short circuit current up to the maximum limit value can be interrupted safely. After its occurrence it must be possible to switch on one additional time onto the not yet eliminated short circuit and again interrupt this short circuit current again safely. The switch does not have to be functional any more after this second interruption. A switch specified for I<sub>CS</sub> must still be capable to protect the circuit and be further usable within certain limitations.

@@ Line 239: / Line 239: @@
 Relevant experiments have shown that combined effects of synchronism, phase sequence and switching delay can, under severe adverse conditions,
-lead to extreme damage, especially on at least one of the phases or poles. They are the cause of early failure of this phase and therefore the complete switching device and can happen as early as after only 30% of the normally expected lifetime. Because of variations in the mechanical characteristics of switching devices from manufacturing processes life testing cannot be performed on one device alone. Only statistical analysis of tests from multiple device samples can be used as reliable results. Such a procedure is however time consuming and costly. If however every single switching operation during a test is monitored for bounce behavior, on- and off-switching synchronization and related phase sequencing and phase delays, the arc moving behavior, and especially arc energy which is transferred during make and break arcing to the contact pieces, and then these data are properly analyzed, it is possible to assess a specific contact material from a test in only one device alone. Only statistical analysis of tests from multiple device samples can be used as reliable results.
+lead to extreme damage, especially on at least one of the phases or poles. They are the cause of early failure of this phase and therefore the complete switching device and can happen as early as after only 30% of the normally expected lifetime. Because of variations in the mechanical characteristics of switching devices from manufacturing processes life testing cannot be performed on one device alone. Only statistical analysis of tests from multiple device samples can be used as reliable results. Such a procedure is however time consuming and costly. If however every single switching operation during a test is monitored for bounce behavior, on- and off-switching synchronization and related phase sequencing and phase delays, the arc moving behavior, and especially arc energy which is transferred during make and break arcing to the contact pieces, and then these data are properly analyzed, it is possible to assess a specific contact material from a test in only one device alone.
 ====<!--13.4.2.4-->Switching Capacity====

@@ Line 239: / Line 239: @@
 Relevant experiments have shown that combined effects of synchronism, phase sequence and switching delay can, under severe adverse conditions,
-lead to extreme damage, especially on at least one of the phases or poles. They are the cause of early failure of this phase and therefore the complete switching device and can happen as early as after only 30% of the normally expected lifetime. Because of variations in the mechanical characteristics of switching devices from manufacturing processes life testing cannot be performed on one device alone. Only statistical analysis of tests from multiple device samples can be used as reliable results. Such a procedure is however time consuming and costly. If however every single switching operation during a test is monitored for bounce behavior, on- and off-switching synchronization and related phase sequencing and phase delays, the arc moving behavior, and especially arc energy which is transferred during make and break arcing to the contact pieces, and then these data are properly analyzed, is it possible to assess a specific contact material from a test in only one device alone. Only statistical analysis of tests from multiple device samples can be used as reliable results. Such a procedure is however time consuming and costly. If however every single switching operation during a test is monitored for bounce behavior, on- and offswitching synchronization and related phase sequencing and phase delays, the arc moving behavior, and especially arc energy which is transferred during make and break arcing to the contact pieces, and then these data are properly analyzed, is it possible to assess a specific contact material from a test in only one device.
+lead to extreme damage, especially on at least one of the phases or poles. They are the cause of early failure of this phase and therefore the complete switching device and can happen as early as after only 30% of the normally expected lifetime. Because of variations in the mechanical characteristics of switching devices from manufacturing processes life testing cannot be performed on one device alone. Only statistical analysis of tests from multiple device samples can be used as reliable results. Such a procedure is however time consuming and costly. If however every single switching operation during a test is monitored for bounce behavior, on- and off-switching synchronization and related phase sequencing and phase delays, the arc moving behavior, and especially arc energy which is transferred during make and break arcing to the contact pieces, and then these data are properly analyzed, it is possible to assess a specific contact material from a test in only one device alone. Only statistical analysis of tests from multiple device samples can be used as reliable results.
 ====<!--13.4.2.4-->Switching Capacity====

@@ Line 219: / Line 219: @@
 ====<!--13.4.2.2-->Temperature Rise====
-Testing for temperature rise is required only for switching devices in the new stage. During use however over the entire life of the device no damages due to temperature rise are allowed in the device or at ist terminal points.
+Testing for temperature rise is required only for switching devices in the new stage. During use however over the entire life of the device no damages due to temperature rise are allowed in the device or at its terminal points.
 <figure id="fig:Maximum movable bridge temperature rise for different contact materials">
 [[File:Maximum movable bridge temperature rise for different contact materials.jpg|right|thumb|<caption>Maximum movable bridge temperature rise for different contact materials in a 132 kW contactor after high load (AC-4) switching

← Older revision		Revision as of 11:45, 9 January 2023
Line 248:		Line 248:

	To safely withstand short circuit currents high requirements are imposed on the weld resistance of the materials used for the mating contacts. During short circuit switching the contact force between the contacts pairing is reduced by electromagnetic forces. Above a certain device specific current value the contacts will separate. This generates an electrical arc with contact material melting at its root points. During the next closing of the contacts this can cause contact welding, prohibiting the opening of the contacts during a subsequent short circuit and therefore eliminating the safety function of the switching device.		To safely withstand short circuit currents high requirements are imposed on the weld resistance of the materials used for the mating contacts. During short circuit switching the contact force between the contacts pairing is reduced by electromagnetic forces. Above a certain device specific current value the contacts will separate. This generates an electrical arc with contact material melting at its root points. During the next closing of the contacts this can cause contact welding, prohibiting the opening of the contacts during a subsequent short circuit and therefore eliminating the safety function of the switching device.
		+	<br style="clear:both;"/>

← Older revision		Revision as of 11:44, 9 January 2023
Line 34:		Line 34:

	The electrical life of a motor switch is influenced primarily by arc erosion which is generated during make and break arcs on the contact surface. During AC-3 testing, for which the make current is six time the nominal rated current, the arc erosion is mainly caused by the make arcs, especially if frequent contact bounces > 2 ms occur. Therefore the bounce characteristic of switching devices primarily used for “normal” use in switching on and off electrical motors is of critical importance. If make and break currents are the same, as in the ultilisation categories AC-1 and AC-4, the break erosion dominates the arc erosion so much that make erosion can be neglected.		The electrical life of a motor switch is influenced primarily by arc erosion which is generated during make and break arcs on the contact surface. During AC-3 testing, for which the make current is six time the nominal rated current, the arc erosion is mainly caused by the make arcs, especially if frequent contact bounces > 2 ms occur. Therefore the bounce characteristic of switching devices primarily used for “normal” use in switching on and off electrical motors is of critical importance. If make and break currents are the same, as in the ultilisation categories AC-1 and AC-4, the break erosion dominates the arc erosion so much that make erosion can be neglected.
		+	<br style="clear:both;"/>

@@ Line 213: / Line 213: @@
 U = Voltage<br />
 U<sub>r</sub> = Recovery voltage
+<figure id="fig:AC3 contact arc erosion of two differently produced Ag SnO2 contact materials">
 [[File:AC3 contact arc erosion of two differently produced Ag SnO2 contact materials.jpg|right|thumb|<caption>AC-3 contact arc erosion of two differently produced Ag/SnO<sub>2</sub>  contact materials in a 37 kW contactor <b>1</b> Ag/SnO<sub>2</sub>  88/12, produced by conventional powder metallurgy with MoO<sub>3</sub>  additive, extruded <b>2</b> Ag/SnO<sub>2</sub>  88/12, powder manufacturing by the reaction-spray process with CuO and Bi<sub>2</sub> O<sub>3</sub>  additives, extruded</caption>]]
+</figure>
 ====<!--13.4.2.2-->Temperature Rise====

@@ Line 220: / Line 220: @@
 Testing for temperature rise is required only for switching devices in the new stage. During use however over the entire life of the device no damages due to temperature rise are allowed in the device or at ist terminal points.
 <figure id="fig:Maximum movable bridge temperature rise for different contact materials">
-[[File:Maximum movable bridge temperature rise for different contact materials.jpg|right|thumb|Maximum movable bridge temperature rise for different contact materials in a 132 kW contactor after high load (AC-4) switching
+[[File:Maximum movable bridge temperature rise for different contact materials.jpg|right|thumb|<caption>Maximum movable bridge temperature rise for different contact materials in a 132 kW contactor after high load (AC-4) switching
 <b>1</b> Ag/CdO 88/12 sintered
 and extruded
@@ Line 229: / Line 229: @@
 <b>4</b> Ag/SnO2 11.5 WO3 0.5 sintered and extruded
 <b>5</b> Ag/SnO2 11.6 MO4 0.4
-sintered and extruded]]
+sintered and extruded</caption>]]
 </figure>
-For the assessment of contact materials a temperature rise test is frequently performed after a specified number of switching operations accompanied by arcing <xr id="fig:Maximum movable bridge temperature rise for different contact materials"/><!--(Fig. 13.13)-->. The most important characteristic is the measured temeperature rise of the movable bridge contacts. If a certain upper limit of temperature is reached, adjacent plastic components may be irreversibly damaged.
+For the assessment of contact materials a temperature rise test is frequently performed after a specified number of switching operations accompanied by arcing (<xr id="fig:Maximum movable bridge temperature rise for different contact materials"/><!--(Fig. 13.13)-->). The most important characteristic is the measured temeperature rise of the movable bridge contacts. If a certain upper limit of temperature is reached, adjacent plastic components may be irreversibly damaged.
 ====<!--13.4.2.3-->Analysis of the Switching Sequence====