Siemens SAMMS-MV Ultimate Trip Level and Service Factor, Phase Unbalance, Stator Protection

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3 Operating the SAMMS-MV Device

3.13 Ultimate Trip Level and Service Factor

The ultimate trip level is the maximum continuous current that does not cause an overload trip. Any higher current applied indefinitely to an unprotected motor will ultimately damage it. The ultimate trip level for motors with a unity service factor is 110% of the full-load current setting. For motors with a service factor of 1.15, the ultimate trip level is 120%. You can select a service factor of 1.00 or 1.15 with HHC function F6.

3.14 Phase Unbalance

Unbalanced three-phase voltages or loss of one phase can result in unbalanced currents being supplied to the motor. Unbalanced currents include negative-sequence components that produce heat in the motor winding, decreasing the effi- ciency of the motor for a given load. The SAMMS-MV device measures the magnitude of the current unbalance as the maximum deviation from the average of the three-phase cur- rents, divided by the average of the three-phase currents. In case of loss of a phase, the unbalance is 100% in a three-wire, ungrounded system.

With phase unbalance protection enabled, current unbalances of between 20% and 40% cause the Phase Unbalance LED to flash as a warning. If the unbalance increases to above 40%, the Phase Unbalance LED illuminates solidly and overload tripping accelerates. The effect of an unbalance of greater than 40% is to shift the motor protection curve in the direction of faster tripping.

You enable the phase unbalance protection using HHC function F9.

∙Enabled = ON

∙Disabled = OFF

With phase unbalance protection enabled, HHC function F17 displays the percentage of current unbalance. Both functions display OFF if phase unbalance protection is disabled.

3.15Dual Overload Protection (SAMMS-MVX Only)

Because the high-speed and low-speed currents differ in two- speed motors, different full-load current settings are often required. In such applications, use function F5 to select the full- load current for low-speed operation.

3.16 Jam Protection (SAMMS-MVX Only)

Certain mechanical loads, especially those containing gears, are susceptible to jamming. Jam protection can prevent dam- age to the motor and the driven equipment by quickly tripping the motor off-line in the event of a jam. If you have enabled jam protection, you may adjust the jam trip level from 120-400% of IFLC. The jam trip time is 360 msec. SAMMS-MVX is normally shipped with jam protection enabled, with a trip level of 200% IFLC (See Figure 3.11). Jam protection is locked out for 5 times the overload class after a start, speed, or direction change. If the jam limits are exceeded, the motor is tripped off-line and the External Trip LED on the front panel solidly illuminates. You can

enable jam protection using HHC function F23.

∙enabled = ON

∙disabled = OFF

3.17Loss of Load Protection/Warning (SAMMS-MVX Only)

If the running current of the motor suddenly drops below 20 to 95% (adjustable) of its previous reading in 360 msec, a loss of load has occurred. Such a loss of load could be due to a broken belt or loss of back pressure in a pump. Loss of load detection is locked out for five times the overload class time after a start, direction, or speed change (See Figure 3.11). You can select loss of load protection or warning using HHC function F24.

∙protection = ON

∙warning = OFF

With protection selected, detection of a loss of load trips the motor off-line and illuminates the External Trip LED. With warning selected, the motor does not trip off-line and the External Trip LED flashes until the current returns to its former steady-state level or higher. SAMMS-MVX is normally shipped with loss of load protection OFF (WARNING), and with default setting of 50% IFLC.

3.18Process Current Warning (SAMMS-MVX Only)

It is often convenient to have an indication that the load current is above its normal operating level so that the process can be checked and, if necessary, adjusted. You can set the process current warning from 0% (displayed as “OFF”) to 100% of the full-load current with HHC function F22. As long as the motor running current exceeds the process current warning level, the External Trip LED flashes. Process current warning is locked out for five times the class time after a start or a direction or speed change.

3.19 Stator Protection

By selecting the overload class slightly greater than or equal to the motor’s starting time, the motor model defines an energy I2t value. In this value, I equals 600% of the motor’s full load current and t equals the overload class selected.

If the amount of energy exerted by the motor during start, stall or under locked rotor condition exceeds the amount of energy defined by the overload class selected, the SAMMS-MV device will trip. This protects the motor’s winding against excessive heat build up. For example, a typical motor starts within 3 to 4 seconds. By selecting an overload class 4 or 5, you can safely start the motor hot or cold and without nuisance tripping. This also provides protection against stall time exceeding 4 or 5 seconds; assuming the locked rotor current equals 600% of the motor’s full-load current (See Figure 3.11).

3.20 Rotor Protection

Since medium-voltage motors are rotor limited under locked rotor conditions, and stator limited under running conditions, the SAMMS-MV device computes an accurate thermal signa-

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Contents SAMMS-MV Qualified Person Contents Field Service Operation Signal WordsQualified Person About this Manual Advanced Protection for Medium-Voltage Motors SAMMS-MV Device ModelsOverload Protection Using the Standardized Control PanelProgramming Control Circuits SAMMS-MV Model Change settings requires password Yes Remote inputs OneOutputs One Light barsInstalling the SAMMS-MV Device Full voltage non-reversing connection diagram Grounding the Device SAMMS-MV device communications connections Using the Reset/Test Push Button Password ProtectionPerforming a Lamp Test Performing an Overload Relay TestInput Devices Output DevicesCustom Ladder Diagrams Ladder Diagrams Library of Standard Ladder DiagramsSAMMS-MVX Standard control circuits PB1 PB2 PB3 PB4 PB5 PB6 Motor Ambient Temperature Ridethrough Upon Loss of Power SAMMS-MVX OnlyIncomplete Sequence Intelligent Reduced-Voltage Starting SAMMS-MVX OnlyODP motor thermal signature Protection Curves and Overload Classes Seconds Operating the SAMMS-MV 11 Motor protection graph Phase Unbalance Ultimate Trip Level and Service FactorDual Overload Protection SAMMS-MVX Only Jam Protection SAMMS-MVX OnlyRepetitive Starts Ground Fault DetectionStart Inhibit Cooling Time Constants12 Multi-start scenario for an ODP motor Using the Hand Held Communicator HHC Autoreset After a Trip SAMMS-MVX OnlyEmergency Restarting Function KeyFunction Number 5A CT primary current low speed if used Service factor5A CT primary current if used Full load current for OLR No Motor type Overload trip class class 2 throughUsing the SAMMS-MV Device Func- tions Using the Enter KeyUP and Down Keys ON/OFF Default Value Select ground fault pick-up currentMeans warning Select jam pickup current 120-400% Iflc F24 Loss of Load13 Entering and changing passwords F0 Ambient Temperature Program Mode/PasswordsSAMMS-MV Functions F1 Control Circuit Number and Incomplete Se- quence StatusF3 Size for Overload Relay #2 SAMMS-MVX Only Overload Setting Step Default Relay Size RangeF4 Full-Load Current for Overload Relay #1 18 to 72AF6A Motor Type F6 Service FactorF7 Overload Trip Class F7A Cold Stall TimeF9 Phase Unbalance Protection F8 Autoreset SAMMS-MVX OnlyF10 Display Time to Restart F11 Emergency RestartingF12A Ground Fault Pickup Current F12 Ground Fault Protection or WarningSize Pickup Current Default H3A-H3C 7A-I FLC 10A 20A F13 Set Programmable Timer #1F16 Trip Current F21 Reset Motor DataF17 Current Unbalance F18 Display Total Elapsed Run Time of the MotorF22 Process Current Warning Level SAMMS-MVX Only F25 Percentage of Motor Winding TemperatureF23 Jam Protection SAMMS-MVX Only F23A Jam Pickup Current SAMMS-MVX OnlyF27 Address F26 Baud RateTroubleshooting Error Condition Troubleshooting Guide Error Condition Appendix a Technical Specifications Over load Spec ificat ions Stat ist ica l Data Dimensions Catalog Number SAM6 Switch # Function Position 375 Siemens Energy Automation, Inc
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