LSC2 Data Sheet / Manual
Contents
1. 20 to compensate If the input signal now starts to fall the modulating stage has to fall back by 20 before the second stage is switched back off and when this happens the modulating output is stepped up to 80 It must then be required to increase by 20 before the second stage is switched back on It will be seen that the oversizing creates a switching hysteresis which reduces the number of times stages switch on and off in response to the input control signal If the stages are of equal size there is strictly speaking no hysteresis In practice in this controller a small hysteresis of 1 is introduced In conjunction with the timed switching delay function this results in acceptable switching frequency but at the expense of a potential loss of control accuracy Seiting the Oversize The controller must be set up to match the oversize of the modulating stage of the heater battery if applicable The default setting is no oversize To set up the oversize switch on DIP switch 1 8 Setup The 0 5V analogue output terminals 7 and 8 now represents modulating stage oversize 0 100 eg 5V represents a modulating stage of twice the power rating of the other stages which may be monitored on a digital volt meter For 10 seconds after switching on the switch the value transmitted is the previously saved setting and if the switch is switched off again within the 10 seconds this value will be retained After 10 seconds the value transmitted is read from2. 28 to 30 29 No connection Do not make any connection to this terminal 30 Supply Neutral Page 4 Safety and Regulatory Considerations The controller must be wired in accordance with electrical standards applicable in the country of installation When controlling heating loads it is important to consider the effects of loss of control due to a fault eg the heating power being turned fully on If this could result in a dangerous situation then independent means of monitoring the load and removing power should be fitted This is a requirement of international standards Control of thyristors in single cycle mode gives rise to harmonic currents and electrical noise and it should be ascertained that these fall within acceptable limits for the application System Configuration Options and Requirements Two versions of the controller hardware are available for use with thyristor only systems or contactor thyristor systems Typical wiring schematics for a 3 stage system of each type are given Contactor Thyristor Control This is the lowest cost option and is most suited to loads which do not vary rapidly or tend to stabilise ata more or less constant value for long periods The controller is fitted with relays to operate the contactors A single modulating thyristor stage is used stage 1 and output 1 to exactly balance the load demand Note also this corresponds with mode 1 operation in the all thyristor systems as below The opera
3. 3 line control the ones in the typical schematics have only 2 line control the controller power supply may be derived across two of the lines via a step down transformer as shown in the schematics or connected line to neutral DIP switch 1 2 must be set to match as there is a phase shift of 30 degrees between line line and line neutral If the thyristors have only 2 line control the power supply must be derived across the two lines which are controlled by the thyristor as shown in the schematics This is to avoid the need to know the supply rotation Line neutral operation is not available With this proviso the supply rotation is immaterial in all cases DIP switches 1 3 and 1 4 must be set to match the load configuration When operating with burst fire control DIP switch 1 6 may be switched on which unsynchronises the logic output from the mains cycles The phase relationship of the controller power supply to the load power supply is then immaterial and the setting of DIP switches 1 2 to 1 4 will have little effect It may be beneficial to use synchronous operation particularly with fast Page 6 cycle rates as the synchronous algorithm used is designed to maintain load balance and eliminate small DC components from the load current If the supply to the controller is phased correctly it allows the flexibility to change to single cycle operation if found desirable If synchronous operation is chosen then the power supply connection and DIP swi
4. by ramping its output at the rate set on potentiometer P2 As it is the modulating stage reaching either zero or full output which triggers stage switching this function may be used in addition to or instead of the stage switching delay to control the rate at which load power can be increased or decreased With DIP switch 2 8 on The ramp function only operates for 30 seconds from power up of the controller 1 minute for software version CU23E5R5 and later The modulating stage responds to a step change in input demand upwards by ramping its output but responds immediately to a step change downwards This function can be used to limit the rate at which power is applied to the heaters on initial power up Particularly in all thyristor systems with progressing modulating stage it can be used to avoid shock heating any of the heater banks In either case P2 adjusts the time taken for the controller given a step change from 0 100 in input signal to switch on all stages independent of the number of stages ramping the modulating stage after each time another stage switches in The time is adjustable from Os to 50s In master slave applications the potentiometer P2 is only set on the master unit Auto Manual Function This function enables an optional manual potentiometer to be connected as shown in the typical schematics Control by the potentiometer is selected by activating digital input 1 A 0 5V signal may alternatively be fed into
5. degree 2 withstand voltage 3 750V RMS 50Hz Between analogue inputs no isolation Between any 2 digital inputs no isolation Between any 2 logic outputs no isolation Between analogue inputs and logic outputs withstand voltage 1500V RMS 50Hz Between analogue inputs and digital inputs withstand voltage 1500V RMS 50Hz Between digital inputs and logic outputs when digital inputs are fed from a separate supply eg a plc system withstand voltage 1500V RMS 50Hz Ordering Codes There are four options for standard units Stand alone or master controller for use with thyristor contactor systems 1 logic and 5 relay outputs Stand alone or master controller for use with all thyristor systems 6 logic outputs LSC2 Relay LSC2 Logic LSC2 Relay Slave Slave controller with relay outputs for use with contactors 5 relay outputs LSC2 Logic Slave Slave controller with logic outputs for use with thyristors 5 logic outputs Special versions of software and minor hardware variations can be made available to enable special sequences or combinations of load types and size These will have additional references added to the order codes User Configuration Before putting the controller into service it is important that all the information on preset potentiometers jumper and DIP switch settings has been read and appropriate settings chosen Failure to do so may result in unpredictable operation Furth
6. potentiometer P2 and may be adjusted to the value required The previous stored value is now lost When it is set correctly switch DIP switch 1 8 back off The value is then stored in EEPROM and the analogue output reverts to its normal function Modulating Stage Thyristor Firing Modes The logic output offers two firing modes burst fire and single cycle burst fire Burst fire control is a method of controlling the load power by switching the current on and off The current is on for a number of supply cycles and off for a number of cycles The load power is varied by varying the ratio of on time to off time In burst fire mode the fastest cycle time offered by this controller is 0 3s at 50 duty cycle corresponding to approximately 8 cycles on and 8 cycles off at 50Hz Potentiometer P3 may be used to adjust the cycle time between 0 3s and 20s Single cycle burst fire control is the fastest type of burst fire control possible At 50 duty cycle power one mains cycle on is followed by one off Above 50 power only one mains cycle is allowed to be off before another on cycle Any number of on cycles may follow each other consecutively Below 50 power only one mains cycle is allowed to be on before another off cycle Any number of off cycles may follow each other consecutively The average ratio of on to off cycles is controlled to obtain the required average load power Single cycle control can be used for fast response loads or to minimise the effec
7. Caledon Controls Ltd Pee sae reese Unit 2 Block 4 Castlehill Ind Est Carluke Lanarkshire Scotland ML8 5UF Website www caledoncontrols co uk Email info caledoncontrols co uk Data Sheet and User Manual LSC2 Multi stage Load Sequencing Controller Revision 4 Up to 6 Stages in one unit Upto 11 stages with slave unit Directly interfaces to low cost logic input thyristor stacks or to contactors Built in Burst fire and Single Cycle Control Algorithms Allows modulating stage oversizing for stable control Stage rotation facility to balance heater usage Galvanically isolated digital inputs and outputs Application The load sequencing controller is designed for use with a large process heating system which is split into several banks of heaters all of which apply heat input to the same heating load The controller balances the required heating demand by switching on the number of stages heater banks which most nearly match the demand and modulating one additional stage to make up the difference Versions are available with combined relay logic outputs and all logic outputs A single analogue output is also provided Relay logic types are used with contactor stages 1 modulating thyristor stage all logic outputs are used when all the stages are controlled by thyristors The analogue output may be used to drive one modulating thyristor which accepts a standard analogue input signal if preferred The
8. NPN 9 Stage 1 Logie Ouipurs pull down transistors These outputs are therefore connected to the negative side of the logic 9 9 p input on the thyristor trigger The common positive for these signals is on terminals 21 and 22 The emitters of transistor logic outputs are commoned in the controller and connected to terminals 18 and 19 4 Unused terminal to maintain creepage and clearance distance between electrically 1e Nolconnection separated circuits Stage 2 Logic Rela 11 aren J y The type of output must be chosen at the time of ordering 12 Stage 3 Logic Relay Relay outputs are normally open contacts One side of all the relay contacts is commoned output and brought out to terminal 16 Contactors or slave relays operated by these relay outputs Stage 4 Logic Relay must have suppressors fitted me output Stage 5 Logic Relay Logic outputs are the collectors of NPN pull down transistors These outputs are therefore 14 output connected to the negative side of the logic input on the thyristor trigger The common positive for these signals is on terminals 21 and 22 The emitters of these transistor outputs 15 Bee Logic Relay are commoned in the controller and connected to terminals 18 and 19 outpu 16 Relay Common Common for outputs 2 6 when these are specified as relay outputs 17 No connection Unused terminal to maintain creepage and clearance distance between electrically separated circuits 18 Aux power supply OV 19 The auxiliary
9. ONTACTOR CONTACTOR Contactor coils oa must have suppressors fitted Typical wiring schematic 3 stage contactor system with modulating thyristor stage STAGE 1 MODULATING STAGE 3 Line3 gt Line2 gt Line1 gt Control Transformer N AUTO MANUAL gt OP6 24V SIGNAL gt OP5 FROM PLC OP4 OP3 OP2 12V OP1 12V MANUAL POT Staging Controller THYRISTOR THYRISTOR THYRISTOR iS le be Typical wiring schematic 3 stage all thyristor system STAGE 1 STAGE 3 Page 9 The following diagrams show representations of current waveforms for burst fire and single cycle burst fire operation The heavily outlined portion of the sinusoidal train indicates when the thyristors are switched on and the lig
10. ation not standard burst fire 7 If switch 5 Off All stages rotate Use only with all thyristor systems ea U hen st 1 is a fixed thyrist dulating st d st 2to6 switch 6 is se when stage 1 is a fixed thyristor modulating stage and stages 2 to off on Snipstages Ao ororatg are relay stages for use with contactors i Off No function When on the modulating stage progresses from one output to the next as If switch 5 5 each new stage is switched on with increasing input signal Only applicable is off On Progressing modulating stage for systems in which all stages are thyristor controlled Off R mei When off the ramp function operates all the time for both increasing and Bee NOTA waySion decreasing input signal and serves to slow the operation of the control 8 3 When on the ramp function only operates for 30 seconds after first power On Ramp function only operates at up and only for increasing input signal It serves to limit the rate of power up application of power on first switch on See section on ramp function Page 3 Terminal Function List Terminals marked have no function on slave units The 5 outputs available on slave units are on terminals 11 to 15 VE TUTE Function Notes Number 1 Saroia Accepts the setpoint signal power demand from a temperature controller Signal type p i determined by JMP1 and DIP switch 1 7 sett
11. ctor stages stages 2 to 6 will rotate every 5 hours This will even out the usage of the heaters over a period of time For example in normal use without rotation it might be that stage 2 is on all the time but the other stages are hardly ever used By rotating the stages they each get used in turn This corresponds with mode 2 below All Thyristor Control This is a more versatile form of control Only one of the stages is modulating at any one time but the non modulating stages are also switched by thyristors This is more satisfactory for loads which vary frequently as there is not the switching life problem associated with contactors The controller offers 4 modes of operation with all thyristor control using the logic outputs although mode 1 may use the analogue output to drive output 1 The modes are set using DIP switch 2 5 2 6 and 2 7 Although mode 2 with slow stage rotation is available in master slave configuration it is of restricted use as the stages on the master will rotate as a group and the stages on the slave will rotate as a completely independent group Mode 3 is not available in master slave configuration Mode 1 Fixed modulating stage DIP switch 2 5 2 6 2 7 off The modulating stage is always stage 1 output 1 The other stages are switched on in order as the power demand analogue input signal to the controller increases The thyristors may all be logic input types or alternatively the modulating stag
12. d from the unit Output signal Non modulating stages Relay or logic signal specified at time of ordering Relays rated 250V AC 2A Contactors or slave relays connected to relay outputs must have suppressors fitted around their coils Logic signal for use with zero voltage switch on thyristors Galvanically isolated from inputs Nominally 12V fed via 470 ohm Modulating stages Logic signal for use with zero voltage switch on thyristors Galvanically isolated from inputs Nominally 12V fed via 470 ohm Analogue signal 0 5V Digital input signal 1 Contact closure or transistor pull up down 24V logic switches unit to manual operation Digital input signals 2 4 Contact closure or transistor pull up down 24V logic Unallocated for use with special software versions Indicators LED indicators for power manual operation selected manual inputs active outputs on Safety Standards Complies with European Low Voltage Directive and major international standards Pollution degree 2 Overvoltage category 2 to IEC 664 EMC Standards Complies with European EMC Directive for operation in an industrial environment Isolation between electrically separated circuits 115 230V power input to other ports double insulated 300V overvoltage category 3 pollution degree 2 withstand voltage 3 750V RMS 50Hz Relay outputs to other ports double insulated 300V overvoltage category 3 pollution
13. e may be an analogue input type It is less important than when using contactors that the modulating stage be oversized as other stages can be switched frequently However better control may be obtained if the modulating stage is oversized as there will always be time delays associated with the heating and cooling of heater elements etc as stages are switched in and out Mode 2 Slow stage rotation DIP switch 2 5 on 2 6 2 7 off As mode 1 except that every 5 hours the role of the stages rotates 1 stage ie on first rotation stage 2 becomes the modulating stage stage 3 takes on the role of stage 2 and stage 1 becomes the last switched stage This helps to even out the use of the heater banks over a period of time At the time of rotation the new outputs take up the values of the ones prior to rotation All stages must be the same size Mode 3 Fast stage rotation DIP switch 2 5 2 6 on 2 7 off The function of the outputs is rotated every 2 seconds For example consider a 6 stage system The signal level might be set so that 2 stages are required to be on and the modulating stage is required to be at 50 power In the standard mode Output 1 would be modulating outputs 2 and 3 would be on and outputs 4 5 and 6 would be off In mode 3 after 2 seconds output 1 would be off output 2 would be modulating outputs 3 and 4 would be on and outputs 5 and 6 would be off After a further 2 seconds Outputs 1 and 2 would be off output 3 would be modulat
14. er information on the settings is given in later sections of this manual Preset Potentiometers P1 Stage switching time delay P2 Ramp time 0 25s to 1 minute prevents rapid cycling of stages 0 50s see section on Ramp Function In setup mode sets modulating stage oversize 0 100 P3 Burst fire cycle time 0 3s to 20s at 50 duty cycle Jumper and DIP Switch Options Settings Jumpers Analogue Input Selection Off On JMP1 A 0 5V 0 10V JMP1 B Voltage Input Current Input connects a 250 resistor across the input Set mp 1A off for 20mA span For signals with 20 zero offset 1 5V 2 10V 4 20mA set DIPswitch 1 7 on Page 2 DIP Switch 1 Function Notes Switches 1 2 to 1 4 must be set correctly for the modulating logic output s to operate correctly in single cycle mode The controller power supply must also be wired correctly to match the setting on switch 1 2 The switches must also be set correctly for the logic output to operate correctly in burst fire mode unless switch 1 6 is on in which case the setting of these switches and the power supply connection is immaterial If the analogue output is used for the modulating stage the setting of these switches and the power supply connection is immaterial Off Controller power
15. hter portion indicates when they are off The waveforms show zero voltage and thus current switch on and zero current switch off and are the waveforms obtained in single phase operation which are sinusoidal NAAN AAAAAA A NAAA ANANA AA NAAA ANAA AAA AAN NA A ff ums J VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV Standard burst fire 25 power n AAAA AAAA Standard burst fire 50 power 5 AUAU A AAAA AAA AAAA A A A A NAA AAAA AN A VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV Standard burst fire 75 power BAD A AAA AA ALS Single cycle burst fire 25 power IN AS AN NNN Single cycle burst fire 50 power PAPPLDPAPP APPA S Single cycle burst fire 75 power Page 10 The following diagrams show current waveforms for single cycle control in 3 phase systems at approximately 50 power 1 cycle on followed by 1 cycle off In 3 wire systems the waveforms are no longer true sine waves The controller ensures that the average current on all 3 lines is the same and that there are no DC components In a 4 wire system the line waveforms are sinusoidal but this apparent advantage neglects the fact that the neutral current is far from sinusoidal The rather oddly shaped waveshapes are also obtained in standard burst fire mode at the beginning and end of the burst Line 2 on Lines AA Uncontrolled Ny Line 1 3 wire system 2 line control Line 3 frente Line 1 3 wire s
16. ing 2 OV OV common for analogue input signals manual potentiometer and analogue output 3 5V Output May be used to energise a 10K potentiometer connected to the manual input Accepts a 0 5V signal when the controller is in manual mode It is advisable to use a screened cable for the leads to the manual potentiometer particularly if they are longer than 4 Manual Input 1 metre to avoid interference pick up which could cause jitter when switching between stages The screen should be grounded adjacent to the controller or to terminal 6 if this is grounded 5 OV OV common for analogue input signals manual potentiometer and analogue output Not a safety earth May be connected to chassis to improve EMC noise immunity For good performance should be connected to the metal chassis adjacent to the controller using a 6 Functional Earth cable not greater than 250mm 10 long and of at least 1mm cross section This may be done easily by fitting a DIN rail mounted earth terminal adjacent to the controller assuming the chassis is unpainted 7 Analogue cutout 0 5V signal which represents the output value of the modulating stage or is used to drive the g P slave controller in master slave operation 8 OV OV common for analogue input signals manual potentiometer and analogue output Stage 1 output is always a logic output for driving a thyristor stack and in thyristor contactor systems is always the modulating stage Logic outputs are the collectors of
17. ing outputs 4 and 5 would be on and output 6 would be off Page 5 etc This operation is only suitable for use with single cycle control and if heaters are distributed around a vessel ensures that the heat input is evenly distributed All stages must be the same size Mode 4 Progressing Modulating Stage DIP switch 2 5 2 6 off 2 7 on The modulating output progresses as the demand increases For example consider a system with 4 equal stages Up to 25 power demand only output 1 is on and modulating Between 25 and 50 power output 1 is full on and output 2 is modulating Between 50 and 75 power outputs 1 and 2 are full on and output 3 is modulating Between 75 and 100 power outputs 1 3 are full on and output 4 is modulating This mode only operates with equal stages and there is no hysteresis between stages The switching delay time and ramp function operate as standard Oversizing the Modulating Stage Most heater batteries are designed with all stages having the same power rating From a control point of view there is an advantage particularly in thyristor contactor systems to having the modulating stage oversized relative to the other stages Consider the case where the relative sizes of the modulating stage and the other stages are 100 80 As the input signal rises from zero the modulating stage output will increase until it is fully on At this point the second stage is switched in and the modulating output is cut back to
18. iven off the relays in the controller Terminal 6 functional earth should be earthed to the metal chassis of the control panel adjacent to the controller using a short length of 1mm cross section cable This may be achieved by using a clamp on DIN rail earth terminal mounted adjacent to the controller This will provide a good RFI earth if the chassis plate is unpainted Alternatively a screw stud may be used z 8 N Ajddnsg 9 g uonoauuoy ON 3 g q iddng 0 s gt 5 E N v dil Bid 5 s d l la a Z d l id N d l Uen ony I g UOWWOD d l c S AZL gt 5 a 3 5 a N 3 a 5 uo oauuop ON E Es e x AO lt S X 2 AO amp uoljaauUOD ON UOWWOD g indino G indjno Checked By A M y yndino indjno Z yndjno UO OSUUOD ON L ndjno 2 5 E E a 3 8 lt T k N cc a gt S AO d o anBbojeuy 5 E S C D 3 2 S S 3 N v S 8 a 3 n yey AO Title d enuen d O AG lt AO m VAN d l u10d aS Caledon Controls Ltd Page 8 Line3 gt Line2 gt Line1 gt Control Transformer m OP1 IS A LOGIC TYPE Lo OTHERS ARE RELAY TYPE AUTO MANUAL Controller THYRISTOR C
19. odulating stage DIP Switch 2 Switches 1 to 4 set the number of stages in addition to the modulating stage For the standard unit not used as a master 5 is the maximum valid number For a master unit 10 is the maximum valid number 5 stages on the master and 5 on the slave In master slave systems the slave switches should be set the same as the master Switch Setting 1 LSB 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 2 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 3 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 4 MSB 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 Number of 1 2 3 4 5 6 7 8 9 10 10 10 10 10 10 non modulating stages When switches are set to 0000 the modulating stage output is fed to all stages master stand alone controller only allowing simultaneous modulating of all stages without rewiring Not suitable for use with relay outputs contactors Off Rontnetion When on the outputs are rotated round the stages For all thyristor 5 systems switch 6 may be set either off or on as required and switch 7 should be off For thyristor contactor systems switch 6 must be off and On Stages rotate switch 7 must be on Switch 6 is only applicable when switch 5 is on The 5 hour rotation may be Off Stages rotate every 5 hours used to balance out the usage of the heater banks over the long term The 6 2 second rotation is used to balance out the heat input when heaters are On Stages rotate every 2 seconds distributed around a large vessel It is only suitable for use with single cycle oper
20. power supply is an unregulated 12V power supply which is galvanically isolated 20 ib econmeaitan from the analogue inputs and the main controller power supply It is used to power the logic outputs and may optionally be used to power the digital inputs in which case they will not be 21 isolated from the logic outputs Aux power supply 12V 22 23 Common for digital inputs The digital inputs are opto coupled and galvanically isolated from the analogue inputs and Digital input 1 Auto logic outputs They may be driven by any signal between 5V and 24V DC typically the 24V 24 TETUR Aea Manual transistor outputs from a plc applied between terminal 23 and the relevant input The when activated LED on common terminal 23 may be either positive or negative with respect to the input so either pull up or pull down plc outputs can be used 25 Digital input 2 To activate by volt free contacts the auxiliary power supply may be used to power the inputs 26 Digital input 3 Link terminal 23 to terminal 22 or 21 and connect the contact between terminal 18 or 19 which becomes the common for all inputs and the relevant input terminal The input is 27 Digital input 4 active when the contact is closed Using the same power supply as the logic outputs loses the galvanic isolation between digital inputs and logic outputs 28 Sipoly Live Either 115V 10 15 or 230V 10 15 50 or 60 Hz Voltage is selected by jumper ppYy assembly immediately above terminals
21. r is connected to terminal 1 on the slave and terminal 8 on the master is connected to terminal 2 on the slave Master slave systems may not be used with fast rotating stage outputs All other modes are possible If slow stage rotation is chosen the stages on the master rotate as a group and the stages on the slave operate as a separate group DIP switches on the slave unit should be set the same as on the master Jumpers 1A and 1B on the slave should both be off Potentiometer P3 should be set as closely as possible to the same value as on the master if burst fire operation is chosen P1 and P2 settings are immaterial potentiometers P1 and P2 have no function on the slave Wiring Practice To ensure good EMC compatibility the following recommendations should be followed 1 Signal wiring should be kept as short as possible and away from power cables In particular long runs of signal cables adjacent and parallel to power cables should be avoided Page 7 Long cables connected to the setpoint input or manual input should preferably be screened with the screen connected to chassis adjacent to the controller In particular it is bad practice to run signal and return wires via separate paths for example routing a common OV cable around several points in a panel separate from the signal wires thus creating a loop aerial for electromagnetic pickup Contactor and relay coils should have suppressors fitted Particularly large contactors dr
22. se with thyristors Modulating logic outputs operate in either burst fire mode or single cycle burst fire mode Both are intended for use with thyristor controllers which accept a logic input signal and have zero voltage switch on The stages may either be of the same power rating or the modulating stage may be oversized which potentially reduces the amount of stage switching required to maintain temperature control A single 0 5V analogue output is provided which in thyristor contactor systems may be used with an analogue input thyristor stack for the modulating stage if preferred this allows a phase angle stack to be used for example In master slave applications the analogue output is only available on the master and is used to drive the input of the slave and therefore is not available for driving a thyristor stack In the case of logic input thyristor only systems in which all the stages have the same power rating the stages may optionally be rotated around the heater banks which helps to balance the total usage of each heater bank Specifications Supply voltage 115V or 230V AC 50 60 Hz 10 15 Power consumption 7VA Ambient temperature 0 50 C Approximate Dimensions 120mm high x 200mm wide x 80mm deep Symmetrical DIN rail mounted Input signal 0 5V 0 10V 1 5V 2 10V 0 20mA 4 20mA link selectable Auxiliary input signal 0 5V manual input may be fed by a 4k7 to 10kQ potentiometer powere
23. staging technique provides the following advantages 1 On large electric heating systems the load is broken into banks of a smaller kilowatt rating and the maximum size of load being switched on or off at any one time is reduced This reduces the magnitude of switching disturbances on supply lines and is particularly useful where the total load represents a significant proportion of the supply capacity 2 On systems where the load demand does not frequently vary over a wide range the non modulating stages may be contactor controlled and the modulating stage controlled by a relatively small thyristor stack Brief Description The new LSC2 controller is based on our successful CU02 controller and includes additional features which had been incorporated over time in various versions of the CU02 controller It also offers isolated digital inputs and outputs and additional digital inputs to simplify the provision of special versions if required The LSC2 load sequencing controller accepts an analogue input signal from a temperature controller which represents heating demand A second input is provided for use with a manual potentiometer The controller provides outputs for up to 6 stages of heating and there is provision for slaving an additional unit to increase the number of stages to a maximum of 11 The stages may be either 5 relay outputs for use with contactors and 1 logic analogue output for a modulating thyristor or 6 logic outputs for u
24. supply in phase with line to line Normal operation 1 2 supply On Controller power supply in phase with line to neutral Cannot be used with 2 line thyristor control off Load connection for 2 line thyristor control Load star Only 2 of the 3 phase lines are controlled by 1 3 or delta connected thyristors The third is directly connected to the load On Load connection for 3 line thyristor control All 3 lines are controlled by thyristors E Off 3 line control 3 wire load connection star or delta Only operative if 1 3 is on Must then match the load On 3 line control 4 wire star load connection connection Off In auto mode the manual input signal has no function In manual mode the manual input signal controls the In auto mode the manual input signal sets an upper output power independent of the auto input control 1 5 n limit on the input control signal This enables this signal input or a potentiometer connected to this input to act as a power limit control Off No function Normally should be off See switch 1 2 above and 1 6 On Modulating logic output signal not synchronised to section on Controller supply connection and mains the mains frequency synchronisation E Off Analogue inputs without offset 0 5V 0 20mA etc On Analogue inputs with offset 1 5V 4 20mA etc Off Normal operating mode In set up mode potentiometer P2 may be used to set 1 8 the oversize of the modulating stage On Setup mode See section on Oversizing the m
25. t of burst fire operation on supply generator speed control If phase angle control is preferred for the modulating stage the analogue output 0 5V may be used to drive a suitable thyristor stack which accepts an analogue input but only in systems operating in Operating mode 1 with fixed modulating stage on output 1 Controller Supply Connection Mains Synchronisation and Typical Wiring Schemes The controller must be adjusted for the correct supply voltage either 115V or 230V 10 15 The setting is adjusted by moving the jumper plug which is on the right hand side of the unit immediately above terminals 28 to 30 to the correct position To gain access undo the 2 screws at the right hand end of the unit remove the cheek and unclip the clear cover 115V is set with the plug moved toward the right of the unit and 230V with the plug moved toward the left of the unit as indicated by the small lines on the PCB which should be alongside the wire links in the plug Typical wiring schematics are given at the end of the manual for 3 stage 3 phase systems The controller logic output for the modulating stage is synchronised to the mains frequency This synchronisation is derived via the controller power supply When operating with single cycle control it is essential that the power supply be correctly phase related to the supply which feeds power to the heaters The thyristors must have zero voltage switch on trigger circuits If the thyristors have
26. tch settings must be adhered to as for single cycle operation Delay between Stage Switching Each time a stage switches either on or off a timer is set which prevents further stage switching until it times out The timer is adjustable by potentiometer P1 between 0 25s and 1 minute The timer prevents rapid cycling of the stages particularly applicable in thyristor contactor systems and ensures that on initial switch on when the input control signal to the controller may be at maximum the load is switched on in stages in a controlled manner It also inevitably means that the load cannot be switched off suddenly by reducing the control signal to zero and if this is a requirement eg in emergency some other means must be provided for cutting the load power The timer should not be set longer than necessary as this may have an adverse effect on control stability The longer the time set the longer the integral time constant in a PID temperature controller will have to be In master slave applications the potentiometer P1 is only set on the master unit Ramp Function This function is controlled by P2 and when it is enabled by setting a time other than zero on P2 the modulating stage is restrained from making step changes in its output The ramp function behaves in two different ways depending on the setting of DIP switch 2 8 With DIP switch 2 8 off The modulating stage responds to a step change in input demand in either direction
27. this input across terminal 4 and 5 Note that there is no isolation between this input and the main control input which shares a common OV rail If DIP switch 1 5 is on then this input sets a limit between 0 and 100 on the controller output when the controller is operating in auto in addition to operating to set the manual power when the controller is in manual Master Slave Operation The standard controller will operate as a master controller if the number of stages additional to the modulating stage set on DIP switches 2 1 to 2 4 is set to greater than 5 The value set here should equal the total number of stages in addition to the modulating stage used by master and slave up to a maximum of 10 Two models of slave controller are available providing either 5 logic output stages or 5 relay output stages A logic output slave should be chosen if the master has all logic outputs and a relay output slave if the master is a relay output unit Slave controllers use similar hardware to the standard controller but have different software When the standard unit is used as a master its analogue output ceases to represent the modulating stage value and instead becomes a retransmission signal to tell the slave unit how many stages to turn on The signal from a temperature controller is fed to the master setpoint input and the analogue output from the master controller is fed to the setpoint input on the slave controller ie terminal 7 on the maste
28. tion of a 4 stage system with equal stage size in response to an increasing control signal input is shown for example in the table below operation is reversed for a decreasing control signal input Input Signal Level Coniroller Action Increasing from 0 to 25 The modulating stage output increases from zero to full on 6 Output 2 switches on and the modulating stage is set back At 25 to zero to compensate Output 2 remains on and the modulating stage increases Beer es pele 30 from zero to full on Output 3 switches on and the modulating stage is set back O At 50 to zero to compensate Output 3 remains on and the modulating stage increases Between 50 and 75 from zero to full on Output 4 switches on and the modulating stage is set back O At 75 to zero to compensate Output 4 remains on and the modulating stage increases Between 75 and 100 from zero to fullior The thyristor may be either a logic input type driven by the stage 1 logic output on the staging controller or an analogue input type driven by the analogue output on the controller It is advantageous if the modulating stage is oversized relative to the contactor stages as this will help reduce the frequency of contactor switching and avoid the situation where the required power demand is met just at the point where one stage is switching on off With DIP switch 2 5 and 2 7 on and DIP switch 2 6 off the conta
29. ystem 3 line control Line 2 re ee a a se Ta F f FA A Fa Line 3f iv op coat N NIG Line 1 a T ET T E NN 4 wire system 3 line control cu27L1R4 Page 11
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