wye-delta and solid state starter application guide
Contents
1. Figure ASSMC FLEX Wiring Diagra Tree Wiro Conta with Optional Isolation Contactor Wye Delta and Solid State Starter Appli Figure SMC FLEX Wiring Diagram Three Wire Control with Shunt Trip Circuit Breaker wrww rockwellautomation com Power Control and Information Selutions Headquarters meas Roel Au 1251 Sah Seid Nie YIII OE LSA AE Fae D ATABAL MMA ste Rd atre tend I Cac pr 3 100 pr Rn eng Keng 28 98 82 58 Ie m2. of the SMC product line are impressive tis equally important to remember that there are stil all the traditional reduced voltage advantages such the mechanical torque and electrical reduction benefits These alone yield additional savings in terms of system maintenance and proactive detection of potins olid State By designing sold tate products uh as the SMC Dea and SMC Flexo be wired inside the Solid Stat delta increased Hp KW capacity can be achieved through the standard product offering It is Starters for important to remember tht the actual curent handling capacity of the device and physical Wiring Inside connecti does not change but s merely due to the physical and electrical relationships of a the Delta E Sizing Figure 7 depicts differences between inside the delta and outside the delta wiring Notice hatin Figure 7 B each SCR and by pass is exposed to a portion of the total current draw of both motor windings attached at each comer of the delta The inside the delta wiring shown as Figure 7A shows how each SCR and bypass contactor is only subjected to the curent of one winding This value as explained earlier is equal to the full load current divided by 1 73 and Solid State Starter Application Guide M PL LN VN VN e SMC wired Det SMC Wired to 3 Lead Delta Motor wit lead motor Figure 7 Inside the Dolta vs Delta Therefore as an example the 480 amp SMC
3. ratio of soft start starting cent level l divided by the full voltage starting curent CR scan Starting Torque Reduction e Wye Delta and Solid State Starter Application Guide Solid State Starting Advantages Table 1 shows the torque output of a motor with a full voltage starter traditional wye deta starter and soft starter at various current imit settings Table 1 Starting Torque and Currents See xen emm x The latest extension to Allen Bradley line of solid state starters is the SMC Delta and SMC These products are specifically designed to offer the basic functions of an electro mechanical wye deta starter the reliability of solid state starting advanced mator protection closed transition starting and significantly smaller mounting panel space then bth electro mechanical and previous solid state starters perceived disadvantage is the fact that the current to torque ratio is less with a solid state starter then with a traditional electro mechanical starter f we look again at Table 1 the Soft Start must be setup for 350 current limit to provide the equivalent starting torque produced in the traditional wye delta arrangement The reason for this is the motor has slightly different torque characteristic while connected in the wye for starting as compared to being connected in the delta The elec
4. 5 KW 20 Hp 1800 RPM motor The full load current is approximately 30 at 400V or 26 A at 480V If we assume that the nominal starting current is 600 of full load current then the resulting inrush current during starting is about 180 A 156 A respectively The resulting starting torque would be 100 of the motors nominal ful load torque Wye Connection With the windings ina wye connection rather than the delta the full voltage applied ine to ine is the same but the voltage across the individual motor windings reduced as shown in Figure 3 The voltage is reduced by the inverse of he square oot of 3 or 57 7 of ful imr Starting Voltage Reductions 077 2 57x480 2 178 For power systems with Line to Line L to L voltage of 400V or 480V the actual voltage across the motor windings is the Line to Neutral L to N voltage of 230V or 277V respectively Wye Delta and Solid State Starter Application Guide Figure3 Voltage Wye Connection The effect of applying reduced voltage across the windings during starting can be best explained by our example Using the wye connection the starting current is proportional to the voltage reduction therefore 4 188 Staring Current Reduction Br 5174 188 sre 51 A Using the information LRA 180 A 156 AJ the wye connection current would be approximately 80 for 400V or 51 A for 480V It is easy to noie the large red
5. CRs to be designed to handle the cunts required for starting and using the by pass contacts to minimize power losses during running This standard feature also contributes to the compact product size while keeping the total required enclosure size to a minimum since heating during running is the same as an mechanical starter Another significant advantage of using a solid state starter is the additional functionality and built in diagnostics available Depending on the product protection features such as overload underload jam stall ground fault detection phase loss open load phase unbalance and shorted SCR are just a few of the available features The device can also protect itself from excessive duty cycles or long starting times with internal ovet temperature protection Lastly some products offer communications capabilities that allow Teal time status and telemetry information to be shared with various SCADA and information systems The most influential driver is the cost associated with applying a starter to a motor While breaking down the costs itis important to remember that the traditional wye delta starter still requires a motor with a silead motor connection While most European style motors have additional costs for this feature NEMA style motors carry a cost adder of about 20 on 1807 frame 5 Hp to 1 a 4497 frame 300 Hp In comparison a soft starter Solution is 5 to 20 more hen a standard full voltage or wye de
6. EM See eee Tow VOLTS ig Mon VOLTS oo ejo e MB inc 9 6 glelloo 8 Figure 4 Sample Motor While investigating existing applications look at the installed starter taking special note of the number of contactors and overloads The majority of traditional wye delta starters will have three contactors two typically the same size and one slighty smaller along with one overload Keep in mind that there are other possible silead motor configurations such as two speed motors which in contrast have two overloads In these cases it is best to compare the system components to the schematics shown in Appendix A and look for ther key indicators such as operating voltage nameplate information and available connection diagrams Though these are the most common configurations there is no limit to the amount of variations or special motors that could exist Therefore in addition to the physical information it is important to realize that 80 of standard IEC style Hz motors have si or twelve leads and are designed for wye delta starting Less then 1 of standard 60 Hz NEMA style motors are wired wye delta and most are special ordered unless larger than the 200 Hp frame size where many manufactures make the connections standard The diagram shown in Figure represents common connection diagram taken from an actual siclead motor In this case all of the wires would be available at the terminal or conduit box The firs
7. Flex is capable of handling a motor connected wyerdelta with a FLA of up to 831 A 480 x 1 73 This increase in current carrying capacity translates directly into an increase in Hp Table 3 shows the maximum Hp and kW supported for several SMC curent ranges based on the connection configuration Wye Delta and Solid State Starter Application Guide Table 3 Horsepower Capacity of Soft Starters arent O 38V AC wx Yo m vv 3 3 T5 1 7 7 LI 2 785 75 75 5 5 T g g E 78 g E E EJ z x 7 E u E 3 J 7 EJ 5 5 7 g 0 7 ER we wr g 3 5 E 7 L3 75 3 39 29 38 39 99 39 39 sop ws 39 9 3 39 x pom Notice that mast increases power capacity occur at the higher current range offering of each product This is primarily due to the integration of the overload into the product The overload current adjustment for a particular product must match the nominal FLA currents of the supported Hp HW range Whether the application is being retrofitted or new it is important to fallow the selection tables for open delta connected controllers Connections and Set up Wiring of the SMC Delta and SMC Flex is made simple due to several product enhancements which aid the connection process Connections are s
8. WHITE PAPER LISTEN THINK SOLVE WYE DELTA AND SOLID a TE STARTER APPLICATION EXPLANATION AND ASSISTANCE FOR APPLYING SOLID STATE SOFT STARTERS IN TRADITIONAL REDUCED VOLTAGE APPLICATIONS Traditional Design Theory Delta Connection Wye Connection Motor Identification Electro Mechanical Wye Delt Solid State Starting Advantage Solid State Starters for Wiring Insi Sing Connections and Setup Application Examples EJ Rockwell Allen Bradley Rockwell software Automation Wye Delta and Solid State Starter Application Guide Introduction The theory of applying reduced voltage to a motor for the purpose of altering the motors torque and power consumption characteristics is an idea that has existed for many years These concepts have flourished mainly due to the need to limit torque and limited generator power distribution capabilities In addition energy conservation initiatives have forced local governments to place mandatory reduced voltage starting requirements on motors rated at 7 5 Hp 5 5 KW and larger Reduced voltage staring can be accomplished through various methods including part winding wound rotor auto transformer wye delta or solid state While many of these techniques require specialty motors or special system components the wye delta and solid state method are the simplest to apply Applications employed throughout the United States differ but over the years the dominant method world wide has
9. been the wye delta or star delta starting technique The latest generation of soft starters and Smart Motor Controllers SMCs offer significant advantages over its predecessors when it comes to applying it in wye delta applications In most cases these solid state products be used to replace or retrofit any of the traditional reduced voltage methods The SMC product line has been specially designed to ake full advantage of solid state technology and advanced features to provide a cost effective modular solution to both new and old reduced voltage applications Power Approximately 75 of the world s power systems are supplied as wye power from the istributi transformer Whether the power is supplied as wye or delta makes litle difference to the system starter components provided there is an appropriate voltage potential and phase Terminology relationship present The diagram shown as Figure 1 illustrates a simple connection scheme of the incoming utility power through the mator Keep in mind that there are many different configurations throughout the world but a wye configured system operating at 380 to 415V is the most common In the United States there is both wye and delta power systems ranging from 240 to 480V AC When this document uses the term wye delta motor configuration it is simply referencing the way in which the motor windings are connected to the power system As we will discuss the physical connection of these win
10. dings has an effect on the actual applied voltage to the windings regardless of the power configuration from the transformer Wye Delta and Solid State Starter Application Guide Figure 1 Simple System raditiona By definition wye delta is a traditional electro mechanical method of reducing the voltage Tradi i applied to the motor during starting While this method has significant advantages over Design Theory ventanal ul tage staring he disadvantage that remus ore enel space ue components and most importantly a motor that has all its winding terminations available to the outside so the wye connection can be created While the term reduced voltage starter is used for the wye delta starting method in actuality the full line voltage is stil being applied to the motor leads The reduced voltage occurs simply because of the electrical characteristic of the Wye vs Delta relationship Wye Delta and Solid State Starter Application Guide Delta Connection The Delta configuration shown in Figure 2 shows the resulting applied voltage on a delta connection This is the most common way a motor is connected for direct on line full voltage starting The motor windings are designed to operate at the nominal full voltage rating which is 400V outside the United States or 480V within the U S 400 V or 400 V Figure2 Voltage on Delta Connection Asan example let s examine the electrical characteristics of a 1
11. h have low initial torque demands are ideal for using these products The time it takes the motor to accelerate the load to full speed is crucial When the transition from start to run takes place before the motor is up to speed there is a surge in current much like an open transition Since the SMCs are closed transition they will not switch to the by pass contactor until the current has fallen below 120 of the motors full load current In the event that the programmed start time has elapsed and the motor has not reached rated speed device will continue to run with the SCR operating at full voltage until the current drops below the 120 threshold During this time the motor and SMC will be subjected to increased thermal energy which could result in an overload trip branch circuit tip or an intemal over temperature fault The easiest way to avoid this problem is to insure that the ramp time is long enough to accelerate the load to full speed before the device transitions I limiting the starting time is the concem then the current limit level should be increased to bring the motor up to speed faster The use of a soft starter wired inside the deta means that a portion of the motor windings are connected to line power at all times This differs from other Soft Starter products where the voltage at the terminals was mainly due to the leakage current of the solid state switching devices CRs As always care should be taken when working in and ar
12. ics to control the voltage and subsequently provide transitionless starting Figure has been employed throughout industry since the 1980s Solid state starters often referred to as Soft Starters have primarily been used on three leaded delta connected motors However the ability to be applied to six leaded motors has always been present The simplest way of explaining this is wye delta starters reduce the voltage to the motor through an electrical relationship and physical connection while solid state starters simply reduce the voltage electrically offering this connection option all six motor leads are brought back to the control just ike an elecro mechanical wye delta starter However the motor is actually always connected in a delta configuration and that means the starting line current to torque ratio is different than a traditional wye dela startet Fora soft starter to replace a wye delta starter it needs to reduce torque limit current during the wye or start mode and then after a fixed time switch to full voltage These requirements can be achieved by using the curent limit ode of soft starting for a specified period of time natin the electo mechanical starter has one fined output 67 7 voltage but the soft starter current iit mode allows several output levels that can be adjusted to match the load requirement The staring torque to curent ratio for a starter wired to a motor varies as the square of he
13. implified because they can be wired Virtually the same as conventional wye delta starter Figure 8 provides simple power wiring diagrams for both sixlead and 12 lead motors Notice that there is a slight difference between the wiring of the two devices with the SMC Fex having an internal connection to the line side located on the load side Additional wiring diagrams with sample control wiring are included in Appendix A Ita and Solid State Starter Application Guide Figure 8 Sample Power Wiring Diagrams Connecting the three incoming power six or twelve motor leads andas few as two contral wires for two wire control or three control wires for three wire contral can complete the wiring Enhancements such as locating the power terminals conveniently on unit and the elimination of costly inter wiring helps to reduce panel space requirements and provides saving significant time in wiring Wye Delta and Solid State Starter Application Guide Application Examples Since these starters are designed to replace standard wye delta starters once the connections have been made simple operation can be accomplished by setting the following starting mode characteristics Start Mode Current Limit For typical wye deta application this may be 350 Start time Desired Start Time Consult the factory for extended start time capabilities Overload Desired Over
14. load class Class 10 common for IEC motors Class 20 for NEMA lt FLA Setting Set the motors full load current Found on mator nameplate With these minimal settings and connections the product can provide all the functions needed To replace a traditional wye delta starter as well as provide all the proper motor protection Additonal functionality and advanced features be configured by referencing the specific product user manual but are not required for the basie setup Since the SMC Delta and SMC Flex were designed to be used in the same type of applications as electro mechanical wye delta starters lets review the ideal reduced voltage starting applications Controlling torque is prime application consideration when applying solid state starters When motor torque exceeds the system requirements extreme wear and reduced of mechanical components can result Failure of components such as couplings gears chains sprockets and belts leads to unscheduled shut downs and lost production The SMC Delta provides four levels of starting current 150 250 300 and 350 while the SMC Flex provides fully adjustable starting current levels from 50 to 600 Common applications which require controlling the starting torque can be found in many industries including material handling HVAC mining and waste water treatment where the main applications are fans pumps conveyors and compressors The HVAC industry is a prime envi
15. lta starter depending on the size The cost differences become les as the motor size increases however the functionality and features increase dramatically A standard full voltage starter offers zero features while a solid state solution provides advanced motor control maximum adjustability diagnostics and built in protective features Though cost savings can be difficult to quantify Table 2 shows how installation alone can produce savings A common thought is that it is more expensive to run six leads to a motor three As you will see the costs associated with the installation are negligible when compared to the savings that can be achieved using the smaller SMC controller in the inside the delta configuration Wye Delta and Solid State Starter Application Guide Table 2 System Installation Breakdown of Costs vs Hp Thre Lead Motor EALLA EA CIT Uist instal Sevings Cat No Pico ceno at No Price X Tapco ss KA EZEL ps er es oos s niv s e wur LE LEI aus pie sus norem zzs mz zu CELI ELS sse women sum su isse zz women ers wei Lat ice Standard sot besed on prs ec Noa 202 aes ct lea sss ptu o THW wes and tal nd irs eed uon th pay etiatn While the highlighted advantages and enhanced features
16. nding on the loading of the motor and the timing of this transition the resulting surge in current and torque could produce electrical and mechanical shocks on the system In some cases the instantaneous curent peaks can exceed even the locked rotor current for short durations Figure shows this effect graphically Electrically the consequence of the instantaneous peaks could be power fluctuations or losses Mechanically the increased torque resulting from the current spike could be enough to damage system components e snap drive shaft Wye Delta and Solid State Starter Application Guide Open Transition Closed Transition Soft Starter nc nc nc Speed speed speed n Figure 6 Current and Speed Relatio Reduced Voltage Methods An alternate method to open transition wye delta starting is called closed transition The theory of operation is identical with the addition of a few components needed to eliminate or reduce the surge associated with the open transition The additional components include a contactor and few power resistors The advantage of this method be seen in Figure as the transition surge is virtually eliminated while the disadvantage is additional components panel space and power consumption A sample diagram of this circuit is provided in Appendix A as Figure 10 The solid state starters offer another technique of reduced voltage starting The use of solid state electron
17. on while stil allowing sufficient torque available at the reduced level to accelerate the load Wye Delta and Solid State Starter Application Guide Important The latest design of SMC products have a built in overload and an integral by pass contactor Application and therefore need to be selected according to he motor they are being applied to Since the bypass is builtin the increased thermal capacity requirement of some applications does not Considerations require the SMC to be oversized One exception is due to the decreased efficiency of fans and heat sinks it may be necessary to derate the SMC products for applications above 6 S00 feet 2000 in most cases simply choosing the next size product wil provide enough thermal capacity to guard against the potential af aver temperature tips However itis important to make sure that the motors full oad curent Asti fals into the devices acceptable FLA adjustment range Soft Starters can be successfully applied on a wide range of applications which require the controlling limiting of torque or the reduction of inrush current A common and more costly altemative to Soft Starters are Variable Frequency Drives which differ in both the theory of operation and functionality Drives have the ability to completely manage the motors torque at any speed Soft starters can only provide control in the form of reduced torque and reduced current during starting As identified earlier applications whic
18. ound the motor connections and leads In some instances where the SCR is shorted or the motor is defective the breaker upstream could be instantaneously tripped off ine when power is applied Two common methods for offering line isolation during this occurrence is the addition of a shunt trip unit on the circuit breaker or an isolation contactor Both methods insure power is disconnected from the SMC and load when the SMC senses a fault condition Wiring diagrams of the two options are shown in Appendix A Ifan isolation method is selected the contactor should be sized for the FLA current of the motor E Wye Delta and Solid State Starter n Guide Appendix A Ed 4 a UCET Figure 1 Traditional Open Transition Wye Delta Starter Wiring Diagram Wye Delta and Solid State Starter Application Guide Figure AZ Traditional Closed Transition Wye Delta Starter Wiring Diagram Wye Delta and Solid State Starter n Guide r 1 Figure A3 SMC Dolta Wiring Diagram Three Wire Control with Optional Isolation Contactor Wye Delta and Solid State Starter Application Guide Figure M SMC Dolta Wiring Diagram Three Wire Control with Shunt Trip Circuit Breaker Wye Delta and Solid State Starter Application Guide A 1 l9
19. ronment for the application of solid state starters due to the history of using the wye delta motor starting method Air handling and centrifugal loads make up the majority of system components and most consist of large Hp motors A solid state starter serves as an ideal replacement for legacy applications while offering contractors and OEM s savings in terms of wiring and installation time and space and Solid State Starter Application Guide Every industry has applications where the advantages of solid state starters can be realized Even simple fan applications have low starting torque requirements Fans can be Either directly connected to the motor or belted The fans that are belted usualy require torque control during starting to eliminate or reduce excessive belt wear as result of slippage during across the ine starting Pumps also have low starting torque profiles The initial torque and acceleration torque be critical in some pumping applications and is usualy determined the design of the pump Some pumps such as those with long shafts connecting the motor to the pump may be damaged if the starting toque is too high The need to control the acceleration torque is evident where shock and vibration is created in the pumping system when the pump is started at fll voltage In some cases the curent limit starting available in the SMC Delta the Pump Control option in the SMC Flx help to significantly reduce the wa
20. t phase leads are numbered T1 and T4 The second phase TZ and TS and the last is numbered T3 and TE Wye Delta and Solid State Starter Application Guide A C MOTOR CONNECTION DIAGRAM STANDARD LEO ETAT CONNECTED Wb Dee COINS SOS Figure 5 Sample Wye Delta Connection Diagram As noted in Figure 4 A for connecting the motor for full voltage leads 1 and connected together forming 1 and connected to L1 Correspondingly leads 3 and 5 as well as 2 and 4 are connected together forming T3 and T2 When connecting the motor for reduced voltage and starting current the leads must be connected in the wye or star configuration By connecting the motor in the star connection leads 4 5 and 6 are tied together and lead T1 T2 and T3 are connected to L1 L2 and L3 While these are common connections always check with the motor manufacture or the user manual to insure the connections are the same before applying power Electro The mst wily ted onfguaton of e electro mecharical wee startar ia ford to yen nsn To pd cic includes thes sopra crc an vod relay Mechanical timer and an interlock A sample wiring diagram is included in Appendix as Figure 9 Wye Delta vs id Tho open tasti t dosti fis method borate tha moto ia menti Solid State disconnected from the line when changing from the wye to the delta configuration This method Starters has one important disadvantage Depe
21. ter hammering effect found in large systems Like fans and pumps some types of compressors need low torque to accelerate to full speed Reciprocation compressors require high starting torque especially when staring under load Other types such as centrifugal and axial vane type require low starting torque because of the design characteristics These are typically started unloaded and are perfect candidates for reduced voltage starting For other types of applications reduced voltage starting may be necessary to limit inrush currents instead of controlling torque The need to limit the inrush current may be due to government mandates power company restrictions distribution system limitations or operation in areas that are adjacent to or within a residential area may need to limit curent during starting to eliminate voltage drops that cause light flicker A good example of this is on pumps for hydraulic elevators in an apartment complex These pumps have low starting torque requirements so limiting curent during starting minimizes any line sags that would have occurred if the pump was started direct on line In instances where limiting the current is more critical than torque the elecro mechanical wye delta starter has only one setting 200 current limit The SMC Deta have has four tument limit settings and the SMC Flex is fully adjustable With this adjustment it is possible to select a level that meets the specific needs of each applicati
22. tro mechanical starter connected in the wye configuration draws 1 3 the line current which results in 33 of the starting torque Referring to the example sed earlier for a 15 KW 20 Hp motor the wye connection current would be 60 51 at 400 480V and 33 of the ful load torque at starting With the SMC 350 curent limitis needed to obtain the same torque output 34 from the motor which results in current of 105 90 A at 400 480V 350962 ise Wye Delta and Solid State Starter Application Guide The electro mechanical wye delta starter actually provides mare torque per line ampere than the solid state starter however the torque is fixed at 33 of the normal starting torque The adjustability of the SMC provides the ability to more closely match the torque requirements of the system to the motor thus providing better control and longer life of the mechanical components The solid state soft starter is inherently a closed transition device and in actuality provides transitionless starting because the motor connection is never removed The advantages of this starting method includes the reduction in components space requirements and the eost needed to minimize torque and current surges when switching from start to run Some solid state starters such as the SMC Delta and 5 come standard witha builtin by poss contactor The built in by pass maximizes power handing capabilities of the product by allowing the S
23. uction in curent however the result of the reduced voltage also means that some starting torque is sacrificed The reduction in torque would be approximately equal to the square of the reduction of voltage across the motor windings of String Torque Reduction t 577 x 100 33 of ful load torque Motor Identification Whether the application is new or exiting identifying wye delta connected motors can be easy The motor nameplate and connection diagram will typically indicate wye delta or star delta but there may also be references to low volts and high volts As discussed previously the voltage plays a big part in the characteristics of wye delta applications This is why the most voltage combinations 220 380V AC and 277 480V AC Physically single voltage wye delta motor will have six leads marked T 1 through 8 In comparison a standard single voltage delta motor has three leads which are marked T 1 through T3 For dual voltage motors the wje deta motor will have 12 leads marked T 1 through 2 whera as the standard delta motor has nine leads through TS Figure 4 shows two common connection diagrams for both a s lead single voltage wye delta motor and a 12 ead dual voltage wye deta motor Wye Delta and Solid State Starter Application Guide v gar A Re Sample AC Motor Connection Diagrams od 6 o 6 ed e 8 6 o e 5 o TET Gm 9 6 VERR
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