Question 1

What are the differences between APC branded and Dell branded Smart-UPS products?

Accepted Answer

Issue: What are the differences between APC branded and Dell branded Smart-UPS?Product Line:Smart-UPSEnvironment: "DL" models, All Serial NumbersCause:APC has entered into an agreement with Dell to produce new Dell branded Smart-UPS. All support is to be provided by APC.Resolution:There are 5 differences between new Dell branded units and APC standard models:1. Dell logo badge on the front panel.2. Dell logo on the box.3. Online Smart-UPS models (DLRTs) ship as towers, with feet and top cover attached, but include the rail kit in the box for versatility. APC standard Smart-UPS Online products come either as a tower (no rail kit) or as a rackmount (no feet). DLRTs are true convertibles.4. Dell SKUs have a blue sticker on their rear panels: 5. All Dell branded units feature a 3-year Hardware and 3-year Battery warrantyAPC provides all post-sales support for these products. Customers should call APC directly rather than contacting Dell tech support.Technical specs are the same between the APC and Dell branded units, with the exception of the DLRT8KRMXLT which features a 6 x L30-30 PDU instead of the 4 x L6-20 and 2 x L6-30 on the standard APC branded unit. Dell-branded SKUDescription / Model NameAPC-branded SKUDLRT192RMBPDell Smart-UPS SRT 192V 5kVA Tower/RM Battery PackSRT192RMBPDLRT192RMBP2Dell Smart-UPS SRT 192V 8kVA Tower/RM Battery PackSRT192RMBP2DLRT192RMBPJDell Smart-UPS SRT 192V Extended Battery Module for 5kVA UPS JapanSRT192RMBPJDLRT192RMXLBP3UDell Smart-UPS RT 192V RM Extended Battery ModuleSURT192RMXLBP3UDLRT192RMXLBPJ3UDell Smart-UPS RT 192V RM Extended Battery Module for JapanSURT192RMXLBPJ3UDLRT3000RMXLADell Smart-UPS SRT 3000VA RM 120V SRT3000RMXLADLRT3000RMXLIDell Smart-UPS SRT 3000VA RM 230V SRT3000RMXLIDLRT5000RMXLJ3UDell Smart-UPS RT 5000VA RM 200VSURT5000RMXLJ3UDLRT5KRMXLIDell Smart-UPS SRT 5000VA Tower/RM 230VSRT5KRMXLIDLRT5KRMXLJDell Smart-UPS SRT 5kVA 200V JapanSRT5KRMXLJDLRT5KRMXLTDell Smart-UPS SRT 5000VA Tower/RM 208VSRT5KRMXLTDLRT8000RMXLI6UDell Smart-UPS RT 8000VA RM 230VSURT8000RMXLI6UDLRT8000RMXLT6UDell Smart-UPS RT 8000VA RM 208VSURT8000RMXLT6UDLRT8KRMXLIDell Smart-UPS SRT 8000VA Tower/RM 230VSRT8KRMXLIDLRT8KRMXLTDell Smart-UPS SRT 8000VA Tower/RM 208VSRT8KRMXLTDLRT96RMBPDell Smart-UPS SRT 96V 3kVA Battery PackSRT96RMBPDLRTA3000RMXL3UDell Smart-UPS RT 3000VA RM 120VSURTA3000RMXL3UDLRTD3000RMXLI3UDell Smart-UPS RT 3000VA RM 230VSURTD3000RMXLI3UDLRTD5000RMXLI3UDell Smart-UPS RT 5000VA RM 230VSURTD5000RMXLI3UDLRTD5000RMXLT3UDell Smart-UPS RT 5000VA RM 208VSURTD5000RMXLT3UDLT1200RMJ1UDell Smart-UPS 1200VA LCD RM 1U 100VSMT1200RMJ1UDLT1500, DLT1500CDell Smart-UPS 1500VA LCD 120VSMT1500, SMT1500CDLT1500IDell Smart-UPS 1500VA LCD 230VSMT1500IDLT1500JDell Smart-UPS 1500VA LCD 100VSMT1500JDLT1500RM2UDell Smart-UPS 1500VA LCD RM 2U 120VSMT1500RM2UDLT1500RMI2UDell Smart-UPS 1500VA LCD RM 2U 230VSMT1500RMI2UDLT1500RMJ2UDell Smart-UPS 1500VA LCD RM 2U 100VSMT1500RMJ2UDLT2200Dell Smart-UPS 2200VA LCD 120VSMT2200DLT2200IDell Smart-UPS 2200VA LCD 230VSMT2200IDLT3000RM2UDell Smart-UPS 3000VA LCD RM 2U 120VSMT3000RM2UDLT3000RMI2UDell Smart-UPS 3000VA LCD RM 2U 230VSMT3000RMI2UDLT3000RMJ2UDell Smart-UPS 3000VA LCD RM 2U 100VSMT3000RMJ2UDLT750JDell Smart-UPS 750VA LCD 100VSMT750JDLX120RMBPJ2UDell Smart-UPS X 120V External Battery Pack Rack/Tower for JapanSMX120RMBPJ2UDLX3000RMLVJ2UDell Smart-UPS X 3000 Rack/Tower 100VSMX3000RMLVJ2U Please see attached sales brochures for images and additional information.

Question 2

What is LSC (loss of service continuity category)

Accepted Answer

LSC stands for: Loss of Service Continuity category The IEC 62271-200 proposes user-oriented definitions and classifications intended to describe how a given switchgear can be accessed, and what will be the consequences on the installation.When the accessibility of the various compartments are known, then the consequences of opening a compartment on the operation of the installation can be assessed; it is the idea of Loss of Service Continuity which leads to the LSC classification proposed by the IEC: “category defining the possibility to keep other high-voltage compartments and/or functional units energised when opening a accessible high-voltage compartment”.Several categories are defined, according to “the extent to which the switchgear and control gear are intended to remain operational in case access to a high-voltage compartment is provided”: LSC1: If any other functional unit than the one under intervention has to be switched off, then service is partial only:LSC2 If at least one set of busbars can remain live, and all other functional units can stay in service, then service is optimal:LSC2A or LSC2B: If within a single functional unit, other(s) compartment(s) than the connection compartment is accessible, then suffix A or B can be used with classification LSC2 to distinguish whether the cables shall be dead or not when accessing this other compartment. If no accessible compartment is provided, then the LSC classification does not applyFor a more complete description please download the Medium Voltage technical guide.

Question 3

My Drive is showing nSt when I power up and we can not get beyond this.

Accepted Answer

nSt is a drive Status. It's not an error or fault, it's just showing the state that the drive is currently in. It represents a freewheel stop. The drives will default to a freewheel stop state if there is something about your application that prevents the drive becoming ready (Rdy).nSt can be caused by a number of different things for different drives and is dependent on the way they have been set up to operate, There are some example situations given below. Look for the explanation that best suits the situation that you have with your set up.In some applications the drive is required to start as soon as the Mains supply is applied, this has a safety implication which must be addressed first by the user, and if it is deemed safe to do so the following set up must be followed correctly or nSt will appear.On ATV12, ATV312, ATV31C and the ATV320 the first thing you will have to do is to remove any run signal that is currently applied. The display will change from nSt to now show Rdy because the run signal has been removed. Then go to the I_O- menu and then into the tCt parameter, here you will have to change the setting from TRN to LEL and press enter to lock this setting in.Now you can link between the terminals +24 and LI1 in this case as soon as the power is applied the drive will start off in the forward direction. If you require it run in the reverse direction the link should be between +24 and LI2.For the ATV61 and ATV71 Go to the menu 1.5 Inputs / Outputs CFG and for the ATV32 it is the FULL > I_O- menu. Then in all three cases you go to 2 Wire Type (tCt) and change to setting from Transition (TRN) to Level (LEL) and then follow the procedure above.In the ATV600 and 900 series you need to go to the menu complete settings, command and reference and set the two wire type to LEL.In the ATV320, It's RDY > CONF > FULL > I_O- > TCT --- Change this from TRN to LEL.A second application is for the drive to be in three wire control, this is where start and stop buttons are used to control the drive. This is achieved by setting tCC parameter in the I - O - menu to 3 wire type, which automatically sets LI1 to stop LI2 to run forward and LI3 to run reverse. This means that LI1 should have a normally closed contact across it, so if for some reason this contact is open the drive will not start and displays nSt. this will disappear when the contact is closed, the drive will then show rdy. Once again, nSt is not a fault, it's just there to let us know that the drive is not ready to run because the stop button is not in the correct state to allow the drive to run.Another application is that an input is set up as a free wheel stop type. When configured this way, this input must be held at 24v to allow the drive to run. If this signal is not at 24v the Stop will be applied and nSt displayed on the front of the drive and will remain on the display until the 24v is restored to the logic input.On the ATV31, ATV312, ATV32, ATV320, ATV61, ATV71, ATV600 and ATV900 series drives the code nSt can also appear when these drives are controlled by a communications system. If the drive is not being told to operate, it will stay at nSt until the controller tells it to run, Depending on the type of network method used.

Question 4

Which is the default user and password for the Modicon M172?

Accepted Answer

If it is the first time you connect to the Modicon M172 via USB cable and the EcoStruxure Machine Expert HVAC asks you for credentials you will need to use this: User: administrator Password: password If you want to connect to the WebServer of the M172 and it asks you for credentials the default is: User: administrator Password: password

Question 5

What are the tripping curves for the NSX breakers?

Accepted Answer

These are available in the full catalogue "Compact NSX" See link below:ComPacT NSX & NSXm Circuit Breakers and Switch Disconnectors from 16 to 630A up to 690V - 2024 Catalogue | Schneider Electric (se.com)More information regarding the graphs and how to read them are on the pages below: NSX 100/160/250 breakers:The TMD trip units are on pages 349-351.The Micrologic 2.2 and 4.2 trip units are on page 355.The Micrologic 5.2, 6.2 and 7.2 units are on page 356.NSX400 and 630 breakersThe Micrologic 2.3, 4.3, 5.3, 6.3 and 7.3 units are on pages 359-360.An example of the format is shown below

Question 6

Which is the software used to program the Harmony ST6 and Harmony STM6 range?

Accepted Answer

The software to program the Harmony ST6 range is EcoStruxure Operator Terminal Expert (former Vijeo XD ). The software can be download from the next link:EcoStruxure™ Operator Terminal Expert | Schneider Electric UK The Harmony ST6 include the next references:•HMIST6200 ( 4.3" W)•HMIST6400 ( 7" W)•HMIST6500 ( 10.1" W)•HMIST6600 ( 12.1" W)•HMIST6700 ( 15.6" W)The Harmony STM6 (modular HMI) include the next references:•HMISTM6200 ( 4.3" W) + HMISTM6BOX•HMISTM6400 ( 7" W) + HMISTM6BOXAfter the installation of EcoStruxure Operator Terminal Expert, the trial version of the software is available for 21 days and will have to beactivated with the commercial license. Once you have the software in order to download the application to the Harmony HMI we can use a microUSB cable like the HMIZG936:HMIZG936 - Harmony ST6, USB transfer cable | Schneider Electric UK For more information please access to https://digicat.se.com/ or direct to the catalog:https://download.schneider-electric.com/files?p_Doc_Ref=DIA5ED2181202EN

Question 7

How to Upgrade Firmware on Smart-UPS Models Using the Firmware Upgrade Wizard

Accepted Answer

Introduction: Most Smart-UPS models support user-upgradeable firmware. Firmware upgrades can provide product improvements, feature enhancements, and cybersecurity remediations throughout the product lifecycle. Important: During a firmware upgrade, battery backup is unavailable. Equipment powered by the UPS will not be protected from power failures. Depending on the UPS model, UPS output power may need to be turned off before the firmware can be upgraded. The Firmware Upgrade Wizard will advise you on how to proceed.Certain UPS models do not support firmware upgrade using a USB connection. To upgrade the firmware of these UPS units using the Firmware Upgrade Wizard, a local connection via serial cable must be used. The serial cable supplied with the UPS must be used.Ensure the computer remains powered on and the communication connection between the UPS and the computer is maintained throughout the firmware upgrade process.Schneider Electric recommends upgrading Smart-UPS On-Line SRT, XP, and XU firmware only when instructed by Schneider Electric Technical Support or when advised through an official Schneider Electric communication. To view different UPS firmware upgrade methods, refer to FA164737. Applicable models: Click to expand and view details The following UPS model families support user-upgradeable firmware using the Firmware Upgrade Wizard. Supported UPS model families CSHSCLSMCSMTSMTLSMXSRTSRTLXPXU As support for additional UPS models is added over time, the list below identifies UPS models that are not currently supported by the Firmware Upgrade Wizard. UPS models that do not support user-upgradeable firmware using the Firmware Upgrade Wizard Smart-UPS Ultra 5, 8, and 10kVA modelsSmart-UPS Ultra Modular models with the prefix SRYLUPS models with the prefixes SU, SUA, SUM, SURT, SURTA, and SURTDSMX750, SMX1000, and SMX1500 UPS models with ID 11 running UPS firmware version 02.x or earlierDevices not supported in the current release: SMT750RMJ1U, SMT2200, SMC2200XLI-BR Firmware Upgrade: The Firmware Upgrade Wizard automatically identifies the connected UPS and selects the appropriate firmware file. Note: Downgrading firmware to an earlier version is not recommended. Important: Do not disconnect the UPS communication cable, reboot the computer, or attempt to turn off the UPS during the firmware upgrade.If a previous version of the Firmware Upgrade Wizard is installed, uninstall it before downloading the latest version. Step 1 Download the latest version of the Firmware Upgrade Wizard ZIP file, and the Firmware Upgrade Wizard User Guide. Step 2 Important: Verify the MD5 checksum of the downloaded Firmware Upgrade Wizard ZIP file. The current MD5 checksum is 47c9f0ebc3482359d16c0ebc1798eae9. Open Command Prompt.Change the directory to the folder where the downloaded Smart-UPS_Firmware_Upgrade_Wizard_v4.3.8v12a.zip was saved: This is typically done using the "cd" command.For example, if the Smart-UPS_Firmware_Upgrade_Wizard_v4.3.8v12a.zip file was saved to the Downloads folder, the command may be: "cd C:\Users\Username\Downloads", or "cd Downloads" Run the command "certutil -hashfile Smart-UPS_Firmware_Upgrade_Wizard_v4.3.8v12a.zip MD5"Verify that the displayed MD5 checksum exactly matches the value shown above.For example: Step 3 The Firmware Upgrade Wizard ZIP file contains the application and all required UPS firmware files. The accompanying User Guide provides detailed prerequisites, instructions, and screenshots. Follow the Firmware Upgrade User Guide to update the firmware of your UPS. Depending on the UPS model and upgrade path, the firmware upgrade process may take approximately 25 to 30 minutes. If the firmware upgrade does not complete, contact Schneider Electric Technical Support. Provide the UPS model, serial number, UPS ID, and current firmware revision.

Question 8

What is the wiring scheme for a Direct on line (DOL) starter when connected to a single phase motor?

Accepted Answer

There are a number of issues:We do not manufacture a complete starter specifically for single phase motors but our 3 phase starters can be wired for single phase applications.Relative to their power output, single phase motors draw much greater current than 3 phase for 2 reasons:1. The supply voltage will normally be 240 or 220VAC instead of 415 or 380VAC as is the norm with 3 phase supplies. As power is the product of voltage x current then the current will have to be 415/240 = 1.73 times as great to achieve the same theoretical power.2. Single phase motors are considerably less efficient than 3 phase so losses are greater and current consumption greater still.This means that typically, single phase motor current will be at least double that of 3 phase motors of similar power output. As the power ratings of our starters are based on 415VAC 3 phase it becomes necessary to base starter selection on the full load current of the motor and NOT the power rating.ReversingIt is possible to use one of our reversing starters with single phase motors but it does require extensive rewiring to do so. This issue is complicated by the fact that there are a number of designs of single phase motors and the method of reversing varies between them. Therefore wiring a reversing starter for single phase operation is possible but can only be advised for those who fully understand the wiring techniques of their specific single phase motors and have the knowledge and experience to work out how to apply that to the reversing starter. Therefore reversing of single phase motors is not covered here.WiringSingle phase motors may have a number of connections in their terminal boxes, for main windings, start windings, capacitors, klixons or PTC devices etc. Regardless of the number of terminals present, they will all feed back to a simple live and neutral feed at some point, and it is in this feed that the starter will be connected so it will not be necessary to interfere with any of these internal connections (as would be necessary if dealing with a reversing starter). An example of the terminal arrangement for a single phase motor is shown below:The method of connection is similar to that of a 3 phase, except that for the motor overload to function properly all three poles must be populated. This is because the overloads have phase loss protection, so expect to see similar current flowing in all three poles. If only 2 poles are populated (live and neutral), the overload will sense no current in the third pole and trip accordingly (this can occur in anything between a few minutes, even seconds, up to 2 hours, according to conditions and circumstances).To prevent this the procedure is to run either the live or neutral (it does not matter which) through one pole of the contactor and overload, loop back up to go through a second pole in the contactor and overload and then to the motor. The remaining power feed wire will go straight through the third pole of the contactor/overload and then to the motor. The control wiring will be as that for the 240VAC coil version of the 3 phase system. The diagram below shows the wiring for a single phase motor and the path through the contactor and overload:Please see the attached diagram for guidance. This diagram illustrates possible wiring using a Tesys D (LC1D****) contactor and Tesys LRD overload (LRD**) and stop control is assumed to be by operation of the stop button on the overload. If a starter incorporating a Tesys K series contactor (LC1K****) is used then the connections between 95/14 and 96/A2 are made internally. In this case the start button connection will be to terminal 95 instead of 14 NOTE : These notes and diagrams provide a schematic method of achieving the control but it remains the responsibility of the installer to ensure that any safety requirements, local legislation and directives, circuit and personnel protection are met and/or provided. Installation of any moving or motorised industrial equipment should only be carried out by qualified persons familiar with electrical and machine safety requirements. Do you want to know more about this topic? Connect with our Experts through our online Community:

Question 9

What does light or dark switching mean when referring to photo electric sensors?

Accepted Answer

Please note - As of 01/09/23 the Telemecanique Sensors range is no longer part of Schneider Electric. This FAQ is now for reference only. For further information and contact details for Telemecanique Sensors, please visit their website; https://www.telemecaniquesensors.com/uk/en There are 3 main types of photo electric sensor used for detecting an object; Diffuse (sometimes also called proximity mode or direct detection). There is also a variation of diffuse called diffuse with background suppression (diffuse with BGS).Retro reflective (sometimes also called reflex). There is also a variation of reflex called polarised reflex (or polarised retro reflective). Through beam (sometimes also called thru' beam). Determining normally open (N/O) or normally closed (N/C) operation? Both the retro reflective and through beam sensors rely on the object 'breaking' the beam in order for it to be detected. Whereas the diffuse system requires the object itself to reflect the light beam.Because of this fundamental difference in the way the sensors detect an object, retro reflective and through beam sensor outputs are the inverse of diffuse sensors. This leads to a lot of confusion. Historically Within the photo electric industry, to overcome the confusion of referring to N/O or N/C outputs, the term 'light switching' and 'dark switching' was introduced; Light switching; A sensor that is light switching switches it's output 'on' when the light beam is returned to the receiver. i.e. If N/O operation is required, a light switching diffuse sensor could be used. Dark switching; A sensor that is dark switching switches it's output 'on' when the light beam blocked from returning the beam to the receiver. i.e. If N/O operation is required, a dark switching retro reflective or through beam sensor could be used. Recent developments To simplify product selection, Schneider Electric (under the Telemecanique brand) pioneered the concept (launched as Osiconcept) of 'object detection' with it's Osiris multimode range of sensors. With these products, irrespective of whether the sensor is configured for retro reflective, through beam or diffuse the output will default to N/O. Another feature of these multimode sensors is the ability to invert the output to achieve a N/C mode of operation.

Question 10

How can I cable to the PNP and NPN type outputs for sensors / detectors, using the wiring diagram?

Accepted Answer

PNP and NPN type outputs are available as 3-wire sensors with a DC voltage power supply (the voltage limits are dependent on the specific sensor): PNP type: switching on the positive voltage load NPN type: switching on the negative voltage load These outputs are typical of photoelectric detectors, inductive proximity and other types of sensors.For a detailed explanation of PNP vs NPN, see the following FAQ: FA142566 PNP output The load (relay coil, contactor relay input, PLC input) must be connected between the "-" negative terminal and the midpoint. The corresponding PLC input is Sink. NPN output The load must be connected between the "+" positive terminal and the midpoint. The corresponding PLC input is Source. Some sensors have two PNP and NPN outputs (4-wire sensors) which are wired according to the diagram below.Note that we no longer sell sensors. Telemecanique Sensors, who were previously part of the Schneider Electric brand, were sold in 2023. You can go to their website - www.telemecaniquesensors.com - for more information, including contact details.

Question 11

Why is Neutral and Earth (Ground) Connection forbidden Downstream from Main Panel?

Accepted Answer

The question is often asked what is the maximum voltage permitted between the Neutral and Earth (Ground) conductor and if the Neutral and Earth can be bridged to achieve a zero value.This can be a difficult topic, in fact in many cases it can be dangerous. As you will see from the attached document, there are many reasons why it is not allowed.

Question 12

What are the differences between snap-action and slow-break contacts in limit switches?

Accepted Answer

Note we no longer sell limit switches so the information given below is for information purposes only. You may still be able to buy Telemecanique limit switches (and some 9007 etc. ex-Schneider Electric ranges) but you'd need to go to them directly. This is their website for contact details and product information: www.telemecaniquesensors.com Snap actionThe speed of travel of snap-action contacts is not related to the speed of operation of the actuator. The actuator pretensions an "overcentre spring" mechanism and it is the spring tension which operates the contact once a certain tension has been achieved. This results in a very fast and assured operation of the contacts as the spring mechanisms "flicks" (or "snaps") over the trigger point and latches the contacts on. A similar action takes place on the release, i.e. as the actuator is released the spring tension reduces but the contacts do not move until the tension has dropped below a certain level, when the spring mechanism will snap the contacts open again.Slow BreakA "slow break contact" is one where the physical movement of the actuator is directly linked to the physical movement of the contact. This can give very precise positioning and synchronization of both make and break points but is susceptible to arcing and intermittent signalling at the crucial make/break position, where actuator movement is slow and/or erratic.Main differences between Snap Action and Slow BreakThe snap action contact mechanism inevitably creates a hysteresis effect, where the closing and opening of the switch have considerable overlap. Please see attached timing diagram example. This does not occur with slow break, as the movement of the contacts is directly linked to the movement of the switch / object.Slow break have a higher minimum actuation speed, to overcome the effect of sustain arcing on the contacts. Note that for applications that cause the switch to open a little and then re-close repeatedly / rapidly, this can reduce electrical durability over time.Both types commonly have positive opening N/C contacts (always check your switch to confirm), but snap action provide an assured signal at slower speeds, whereas slow break rely on the minimum actuation speed. This is why there is potential for intermittent signalling on slow break, if that minimum speed is not adhered to.Slow break can often switch bigger loads and offer higher electrical reliability values compared to snap action but please check product tables / data to confirm this on a case-by-case basis.Sequence of moving contactsTiming Sequence for "Snap Action". Note overlap of switching positions for different directions of travel.Timing sequence for "Slow Break". Note same position for make and break.

Question 13

How does the "Dead man's switch" or "Dead man's handle" position work on a controller handle?

Accepted Answer

Please note that we no longer sell joysticks, so this FAQ is for information only. Technological description The handle grip comprises a fixed part (lower section) and a moving part (upper section).Action on the upper part of the handle grip (pressing down) drives a sliding rod inside the control lever.This rod actuates a moving retainer which causes a change in electrical state of the contact element on the lower part of the mechanism, regardless of the position of the control lever. Operation In normal operation, the operator must maintain pressure on the handle grip to operate the machine.If the operator releases pressure (e.g. feels ill and passes out), even if they are still holding on to it, the electrical contact at the base will change state.

Question 14

What is the difference between the REFLEX mode and the POLARISED REFLEX mode on photo-electric sensors?

Accepted Answer

Note that we no longer sell these devices, this FAQ is for information only. Both systems comprise a transmitter and receiver (usually within a single-body sensor), and a reflector. The transmitter sends a beam which is bounced back by the reflector and detected by the receiver. An object passing through the beam blocks the reflection and triggers the sensing signal.REFLEX mode sensors may not be suitable for detecting reflective objects, as a shiny target may bounce the beam back to the sensor in the same way as the reflector. The sensor may not be able to tell the difference between the target and reflector and will therefore fail to detect the object. For maximum effectiveness the targets should be opaque or near opaque and should not be highly reflective in nature. However, the advantage of reflex mode sensors is that they give relatively long sensing distances.POLARISED REFLEX mode sensors have polarising filters over both the transmitter and receiving sensor. The filters are at 90 deg to each other which means that the receiver cannot see the transmitted beam as it will be blocked by the receiver filter. The reflector turns the polarised light waves through 90 deg so that the receiver can see them. Light bouncing off other objects is not rotated so it will not trigger the sensor. This means that the polarised reflex can be used to detect very reflective surfaces, even mirrors, polished metal and semi transparent materials. However, the sensing distance is shorter than REFLEX.

Question 15

How do I operate a star delta starter with 2 wire control?

Accepted Answer

First it is necessary to understand the difference between 2 and 3 wire control. Most motor systems that require operator action to start a motor use 3 wire control. This is a method by which a pulse of control voltage is applied, usually through a momentary pushbutton or spring return selector etc, to the control circuit. The pulse will bring in a contactor or relay which will electrically latch through one of it's own normally open contacts to hold itself in once the start button is released and the pulse removed. The stop button is usually a normally closed contact in series with the supply to the start button and coil of the latching relay, so that when pressed the contact will open, break the supply to the coil and the relay/contactor will drop out, and remain out, until the start device is again operated. Below is a simple diagram illustrating the principle of three wire control. Two wire control is much simpler, a straightforward on/off switch will do the job. Applying power to the control circuit starts the motor, removing the control voltage stops it. Below is a schematic of how a star delta starter can be operated in two wire control. 96 is the terminal for the NC contact on the overload relay, the run signal will be applied to terminal 95 to enable the overload to switch off the motor in the event of a motor fault. KM1 is the Star contactor, KM2 is the Line contactor and KM3 is the Delta. The timer is most commonly a pneumatic timer fitted to KM2 and will normally operate a few seconds (typically 5-30 seconds) after KM2 has energised. This type of operation will usually be found where a star delta is to be operated by a PLC, a pressure or temperature switch or some other device which is going to provide a simple on/off signal. Although 2 wire operation is theoretically simple, it does introduce some problems. Where the possibility of physical interaction between people and a piece of driven machinery exists it is necessary to prevent unexpected re-starts after an overload reset, power resumption after a power cut, emergency stop reset etc. 3 Wire control achieves this automatically as the latching contactor will drop out after a supply or control interruption and will not restart until another start signal is given. With two wire control the machine will restart immediately when power is restored unless the control signal has first been removed. This may not be an issue on an enclosed system, perhaps a ventilation system with enclosed fans etc but on something like a machine tool, saw, conveyor etc, it is essential that an opportunity is given for an operator to ensure everything is clear before initiating a restart. If control is by PLC or similar it may be possible to build into the software to detect an unintended stop and then require a reset input to the PLC before the PLC can restart the motor. Alternatively, an electromechanical system of de-energise and reset of control voltages could be applied. This may be a suitable solution where motors are controlled by a pressure or temperature switch etc. Attached is an example diagram of how such a circuit might be applied to a pressure switch. In this case, once a start signal has been applied the motor will be under the control of the pressure switch, but after a supply or control circuit interruption it will be necessary to press the start button again to reset the control circuit. Any emergency stop application must be upstream of the overload to ensure that in the event of an emergency stop the control circuit will be de-energised requiring a “Start” signal to reset the control supply.

Question 16

What is the difference between PNP and NPN when describing 3 wire connection of a sensor?

Accepted Answer

Most industrial proximity sensors (inductive, capacitive, ultrasonic and photo electric) are solid state.The term solid state refers to the type of components used within the sensor. Solid state electronic components such as transistors are used to switch the output of the sensor upon detection of an object.Two specific types of 3 wire sensors are available; PNP and NPN. The difference is a result of the internal circuit design and type of transistors used. Refer to attached document for simple explanation of the two.A key point to observe is that PNP and NPN has nothing to do with whether the sensor is normally open (N/O) or normally closed (N/C), i.e. a PNP sensor may be either N/O or N/C as can an NPN be either N/O or N/C.Please note that the subject of this FAQ is specifically related to wiring PNP/NPN outputs for sensors, not to give a detailed understanding of transistor technology. However, for ease of understanding please see attached a page extracted from our Practical Aspects book, showing (in brief) transistor terminology and circuit diagrams. Further learning material regarding PNP and NPN transistors can be found online from several sources. Why two types?The selection of a PNP sensor verses an NPN sensor is determined by the nature of the circuit the device is to be used in. When used in a traditional relay type control circuit, it is normally possible to use either the PNP or the NPN type of sensor as shown below. PNP sensors tend to be more commonly used. WiringTraditional relay type control circuit; Use with a programmable logic controller (PLC).When selecting a sensor to be used with a PLC, it is very important that the sensor matches the type of PLC input card to be used.Two types of input cards exist, those that 'sink' current (also known as positive logic) and those that 'source' current (also known as negative logic). It is worth mentioning, that whilst the terms sinking / sourcing and positive / negative logic are well known in some industries, they are not always commonly used terms. It is therefore important to identify the type of sensor to be used with the PLC card based on the PLC manufacturer's documentation and / or wiring diagrams.Most common in Europe is the 'sinking' type of input, these will be used with the PNP sensor as shown below. Less common nowadays are input cards that 'source', these were popular in Asia and require the NPN type of sensor in order to operate correctly. Many modern PLC input cards can be configured and wired to be either 'sinking' or 'sourcing' although it will usually necessitate all inputs on a particular input card being configured the same. NOTE the dotted line in the following diagram is optional and may or may not be required, depending on your hardware/setup. The key wires to take note of are solid red, black and blue wires.

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