417 Available from: http://www.witherbyseamanship.com/ Timer Relays and Multifunctional Timer Relays Available from: http://www.witherbyseamanship.com/ 43Available from: http://www.witherbyseamanship.com/ 7 Timer Relays and Multifunctional Timer Relays 7.1 Introduction Timer relays and solid state timers are used for various automation appliances and have many timer functions or modes of operation. When troubleshooting, it is important to understand what initiates the time delay when the time sequence starts and when the output relay activates. Figure 7.1 – Timer relays Timer relay CO contacts are identified as either normally open or normally closed and adjacent umbrella symbol shows the direction the time delay operates, ie on relay's energizing or on de-energizing. The following is a description of the four basic types of time-dependant operated contacts: •Normally open, timed closed (NOTC) contact Figure 7.2 a •Normally open, timed open (NOTO) contact Figure 7.2 b •Normally closed, timed open (NCTO) contact Figure 7.2 c •Normally closed, timed closed (NCTC) contact Figure 7.2 d. Normally open, timed closed (NOTC) contact Figure 7.2a The NOTC contact, (coded in diagrams as function digits 15-18), is normally open when the relay is de-energised. The contact is closed by applying power to the relay terminals A1-A2, but only after the relay has been continuously powered for the specified amount of time. In other words, the direction of the contact motion is identical to a regular NO contact, but there is a delay in the closing direction when the relay energises. This type of contact is also known as a normally open on-delay. 15 1816 15 1816 a) b) 15 1618 15 1618 c) d) Figure 7.2 – Basic types of time-dependent relay contacts Normally open, timed open (NOTO) contact Figure 7.2b Similar to the NOTC contact, the NOTO contact is coded in diagrams as function digits 15-18 as it is normally open when the relay is de-energised, but closed without a time delay. The timing action occurs on de-energisation of the relay, ie delaying the opening. This type of contact is also known as a normally open off-delay. Normally closed, timed open (NCTO) contact Figure 7.2c Coded in diagrams as function digits 15-16, an NCTO contact is normally closed when de-energised and opened once the relay has been continuously powered for the specified amount of time. The direction of the contact motion is identical to a regular NC contact, but there is a delay when opening. This type of contact is sometimes known as a normally closed on-delay. Normally closed, timed closed (NCTC) contact Figure 7.2d Similar to the NCTO contact, an NCTC contact coded in diagrams as function digits 15-16, is normally closed when the relay is de-energised. However, the time delay occurs when the relay is de-energised, it is sometimes known as a normally closed off-delay. Timer relay manufacturers incorporate resistor- capacitor (RC) networks in circuits to produce time delays. Advanced timer features can include ‘one-shot’ which produces an output pulse for each transition from de-energised to energised, or ‘recycle’ which repeatedly produces an on/off output while energised. Others are managed either by a single function time relay, Delay on Make, Delay on Break, One-shot Timer, Interval Timer, Recycle Timer, shown as a flash timer in Figure 7.3b. Multifunction timers have two independent internal relays, Figure 7.3c, allowing each changeover contact group to operate independently. 44 • Ships’ Automation Available from: http://www.witherbyseamanship.com/ A1 A2 11 1214 A1 A2 15 1618 a) b) A1 A2 1525 28261816 c) Figure 7.3 – a) Relay contacts coding: Miniature relays changeover contacts b) Single function multi-range time relay c) Multifunction timer relay Unlike the changeover contacts of miniature relays marked with reference numbers 11-12-14, as seen in Figure 7.3a, timer relay contacts are marked in diagrams with relative reference numbers 15-16- 18, 25-26-28 for a second CO contact group, as illustrated in Figure 7.3c. The ‘Window’ on the left of the coil’s symbol and the ‘umbrella’ sign adjacent to the contact’s symbol indicate the timer function. 7.2 Timer Relay Functions and Settings 7.2.1 On-Delay Timer An On-delay timer, illustrated in Figure 7.4a, can also be called Delay on Make, Delay on Operate, Operate Delay, Prepurge Delay and Delay on Energisation. Function charts which are provided by all makers are intended to explain the operating principles. A1 A2 15 1618 a) b) Figure 7.4 – Diagram symbol and On-delay function chart In Figure 7.4b: •The upper line (1) represents a power supply across the A1-A2 timer terminals. The lower stage is marked as off. The Step up line (I) means the power supply is applied (marked as on). The Step down line (II) means the power supply is removed •the lower line (2) represents the contact status, this changes in respect of the power-line (1). The contact status always begins with a neutral configuration of contacts, 15-16 are normally closed, 15-18 are normally open •capital letter T illustrates a value of adjusted time delay, while small letter t introduces a time gap that is less than the adjusted time delay T (in other words, t<T). Taking this into account, the On-delay timer function chart in Figure 7.4b can be studied to define the timer operation principle. 7.2.2 Range and Time Settings for Multi-ranged Time Relays Time delay adjustment for multi-ranged time relays, Figure 7.5, depends on the set up of Range and Time rotary scale values. These vary among manufacturers. Range and Time rotary scale values are often colour coded, Figure 7.5c illustrates black and red colour code used for Kl.Moeller timers. a) b) 45Available from: http://www.witherbyseamanship.com/ c) Figure 7.5 – a) Kl.Moeller ETR4-11-A multi-range time relay b) Relay data sticker c) Range- and Time-dial The time delay is set by the timer rotary switch, as seen in Figure 7.6. The Range must be set first. The appropriate range for the desired time delay should be set. The colour of the range scale chosen dictates the colour of the time scale used, ie a red range value refers to the red time rotary scale and a black range value to the black time rotary scale. Figure 7.6 – The ratio between range and time sectors for Kl.Moeller ETR time relays The examples in Figures 7.7 and 7.8 explain the procedure for two time delays to be set up: 6 seconds and 2 hours. Figure 7.7 – Setting the 6 seconds delay The range is set to 10s. The complete time scale sector (red) shown in Figure 7.6 equals 100% of the chosen range value. So, setting the time rotary scale, step-value should be calculated as: ‘Range value’ / ‘max value of red-coded time sector’ = 10s/10 = 1s As the 10s range is used the ‘time’ digits become defined in seconds, from 0.5s to 10s, so a value of 6 equals 6s. Figure 7.8 – Setting 2 hours (120 min) delay The range scale is set to 300 minutes (black range scale). The time scale values are proportional to the 300 m range scale, so setting the time rotary scale, step-value should be calculated as: ‘Range value’ / ‘max value of black-coded time sector’ = 300 min/30 = 10 minutes. As the 300 min range is used, the ‘time’ scale digits become defined values of 10 minutes (from 1.5 to 30), so a value of 12 equals 120 minutes (12 × 10). 7.2.3 Off-Delay Timers Off-Delay Timers, as the name implies, delay the ‘switching off’ of the contact. Variations in the names may include: Release delay timer, Delay on Release, Postpurge delay and Delay on de-energisation. There are three major types of off-delay timer: •True-off timer •off-delay timer operated with an initiate switch •off-delay timer operated with an initiate loop. To understand the difference, all three flow charts should to be studied. True off timer (Figure 7.9) This is the type used when the time gap is achieved by discharging a capacitor through an adjusted load. Load refers to the operating coil of an inbuilt miniature relay. When the supply voltage is applied at terminals A1-A2, the contacts will immediately changeover. However, when the supply voltage is removed the contacts will not change their status until the adjusted time delay elapses. A1 A2 15 1618 Figure 7.9 – True off timer OFF-delay timer operated with initiate switch Before studying the function chart in Figure 7.10, it is important to be aware that another status-line (3) is added between the power-line 1 and the contact-status line 2. This line is called the initiate switch status line and is assigned with reference B1. It defines the status for the additional signal, a potential that is equal to the supply voltage, applied at the A1 terminal. 46 • Ships’ Automation Available from: http://www.witherbyseamanship.com/ A1B1 A2 15 1618 Figure 7.10 – Off timer initiated with B1 signal The timer operates by applying a supply voltage across A1-A2 terminals (I) and the relay contact state remains neutral (15-16 closed). The contact status changes only when additional voltage is applied at the initiate terminal B1, I’: 15-16 opens, 15-18 close. The status remains unchanged until the voltage is removed from B1 and the timer’s preset time delay T elapses (II - III). OFF-delay timer operated with initiate loop The difference between this timer and an off-delay timer operated with an initiate switch is that there is a loop between terminals Y1 and Z2. Closing the loop with an external control circuit initiates the off function in a similar way as the timer with an initiate signal, illustrated in Figure 7.11. A1 A2 Y1 Y2 15 1618 Figure 7.11 – Off timer operated with an initiate loop between Y1, Z2 7.2.4 Interval Timer An interval timer, Figure 7.12, changes the contact status when power is applied at A1-A2 and this position is maintained until the time delay (T ) elapses. The contacts then return to the neutral state, 15-16 closed. If the power is removed the time delay and output is reset. A1 A2 15 1618 Figure 7.12 – Interval timer on-delayed Interval timers may also be called Interval On, On Interval, Pulse Shaping, Bypass Timer Interval Delay and Delay on Energisation with Instantaneous Transfer. 7.2.5 Recycle Timer A1 A2 15 1618 Figure 7.13 – Recycle timer A recycle timer, Figure 7.13, changes the contact status when power is applied at A1-A2 and continues to switch on and off at regular intervals (T ). Removing the power resets the function. A recycle timer is called a Symmetrical Recycler if intervals are equal. They may also be called Duty Cycling, a recycle timer Repeat Cycle, Delay on Operate and on Release, On/Off Dual Delay, Flasher and Dual-Delay. Each of these functions can have an extension name of either –On or –Off as well as be initiated with applying or removing of steering signals. A complete set of the 35 functions created in this way are included in Appendix 5. All off-timers operate with either an initiate switch or an initiate loop. 7.2.6 Star–Delta Timer The star-delta timer, Figure 7.14, is designed as a control measure for starting-up squirrel-cage motors. Star-delta starters are used in three-phase systems (Chapter 9). When starting heavy electric motors, high initial loads are reduced. 47Available from: http://www.witherbyseamanship.com/ a) b) A1 A2 17 1828 c) Figure 7.14 – a) Kl.Moeller ETR4-51-A Star-Delta timer b) Data sticker c) Contact designation and flow chart The timer employs two separate timing circuits: a variable timing circuit for the changeover from star- to delta- mode (T ) and a fixed timing circuit (tu), Figure 7.14a, with 50 ms for the transition time from de-energising the star-contactor to energising the delta-contactor. The Relay symbol and flow charts are shown on a sticker (Figure 7.14b, c). When the supply voltage is applied across the A1-A2 terminals, the first internal output-relay, contacts 17- 18, energise instantly. Once the time delay has elapsed, contact 17-18 opens, de-energising the first relay and commencing the second fixed time gap of 50 ms (tu). Once 50 ms has elapsed the second output relay, contacts 17-28, close until the supply is removed from A1-A2. In the equipment shown, timing is displayed as a flashing green LED and once the timing is complete, the green LED will exhibit a steady light. The Intermediate Star contact status is monitored by the (Y) LED and the Delta contact status monitored by the (') LED. 7.3 Multifunction Timer Multifunction timers (MFT) are the alternative to a number of single function timers. A variety of functions can be selected using a rotary switch, Figure 7.15c, which displays either a function symbol, eg is referred to as on-timer, is off-timer, is interval-timer or a function-setting digit code. The range and time of rotary switch adjustment procedures are similar to that explained in 7.2.2. a) b) c) Figure 7.15 – a) Multifunction timer Kl.Moeller ETR4-69-A b) Side sticker data c) Function dial’s overview Different units use different function identifications. Figures 7.15b and 7.16 illustrate the function charts for the Kl.Moeller ETR timer series, where each function bears a particular code number. This code uses the third rotary switch, located in the front panel’s slot, Figure 7.15c, to set the function. 48 • Ships’ Automation Available from: http://www.witherbyseamanship.com/ A1/A2A1/A2 B1 0,5s 16 82 22 1281 11 21 42tttt t t t function function t t t t Figure 7.16 – MFT combined function charts The function charts are divided into two columns (Figure 7.16). The functions combined in the left column are initiated by applying the power supply across terminals A1-A2. Functions combined in the right group depend on the initiate switch ‘B1’ status and should be referred to in a similar way as Off-timers. Function charts are available from the manufacturer’s data enclosed with the timer. Figure 7.18 shows some examples. 11 On-delayed 16 On- and Off-delayed21 Fleeting contact on energisation 22 Fleeting contact on de-energisation42 Flashing, pulse initiating 82 Pulse shaping81 Pulse generating A1-A2A1-A2 15-18 tt15-18 B1 Power LED Rel LED 0.5s Power LED Rel LED A1-A2 15-18 B1 Power LED Rel LED A1-A2 15-18 B1 Power LED Rel LED A1-A2 15-18 B1 Power LED Rel LED A1-A2 15-18 Power LED Rel LED A1-A2 15-18 A1-A2 15-18 Power LED Rel LED LED 12 Off-delayed t t t t ttt t t t Figure 7.18 – Kl.Moeller Multifunction Timer ETR4-69-A function charts 7.3.1 Advanced Timer Features Several manufacturers provide advanced timer features such as ‘one-shot’ (one measured output pulse for every transition of the input from de- energised to energised) and ‘recycle’ (repeated on/ off output cycles for as long as the input connection is energised). Others are managed either by a single function time relay or multifunction timer, most of which have two independent internal relays that allow independent operation for each changeover contacts’ group. Figure 7.17 – CT MVS 49Available from: http://www.witherbyseamanship.com/ Figure 7.17 shows a CT-MVS timer by ABB which has a second changeover contacts group, marked with double digits 25-26-28. These are represented in large print, while digits alongside (21-22-24) are in small print. The meaning of this code is: 25-26-28 - time delayed contacts operated together with 15-16-18 as on-delayed; 21-22-24 - instantaneous contacts operated independently on group 1. Up to 16 functions can be performed by a single multifunctional timer. a) Multifunction timing with 16 functions: A - On delay; B - Off delay with auxiliary voltage; C - On and Off delay with auxiliary voltage; D - Flashing start with brake; E - Passing make contact function; F - Passing brake contact function with auxiliary voltage; G - Pulse shaping with auxiliary voltage; H*- Additive on delay with auxiliary voltage; A*- On delay and instantaneous switching; B*- Off delay with auxiliary voltage and instantaneous switching; C*- On and Off delay with auxiliary voltage and instantaneous switching; D*- Flashing start with brake and instantaneous switching; E*- Passing make contact function and instantaneous switching; F*- Passing brake contact function with auxiliary voltage and instantaneous switching; G*- Pulse shaping with auxiliary voltage and instantaneous switching; Y' - Star-Delta function. b) Figure 7.19 – a) Illustrates Siemens Simrel 3RP1505 timer, b) A set of 16 functions available 7.3.2 Programmable Multifunction Timers In the late 1990s, electronic appliance manufacturers began to use logic controlled technology for multifunction timers. The Crouzet TOP 948 programmable multifunctional timer, shown in Figure 7.20, provides a choice of eight initial switch dependant functions which can be preset via the touch screen buttons on the operator interface: A – delay on make Ab – delayed single shot B – single shot C – delay on break D – repeat cycle Di – repeat cycle on time first H – interval T – on delay with memory. Figure 7.20 – Crouzet TOP 948 MFT The timer has a plug-in design and uses the 11-pin or 8-pin 35 mm DIN rail base, the connective features are illustrated in Figure 7.21a and b. The LCD and front panel touch screen buttons allow programming and status to be monitored, operational function, time remaining, time preset value, relay contact status, etc. Time and function adjustments are stored in the EPROM (Erasable Programmable Read Only Memory) and supported with an inbuilt Lithium battery. Each function is defined from function charts, as shown in Figure 7.22. IniReset 0 V67 8 9 10 111 2 3 4 5 Power supply a) 50 • Ships’ Automation Available from: http://www.witherbyseamanship.com/ APower Ini Reset Rel t AbPower Ini Reset Rel CPower Ini Reset Rel DiPower Ini Reset Rel TPower Ini Reset Rel t1t2 BPower Ini Reset Rel DPower Ini Reset Rel HPower Ini Reset Rel t t1t1t1t1 t1t1 t1 + t2 = Toff t1t1 t t2t2t2t2 t2 t2 t Figure 7.22 – Crouzet TOP 948 function charts Ini Reset 0 V 45 6 7 1 2 3 8 Power supply b) Figure 7.21 – a) 11-pin DIN rail base and connection features b) 8- pin DIN rail base and connection features 599Three-Phase Induction Motors Available from: http://www.witherbyseamanship.com/ Available from: http://www.witherbyseamanship.com/ 9 Three-Phase Induction Motors 61Available from: http://www.witherbyseamanship.com/ 9.1 Induction Motors An induction motor works by inducing a current in the rotor by a voltage being applied across the stator winding. This induces a current in the rotor by transformer action and exerts a torque on the rotor. 9.2 Induction Motor Terminal Features The induction motor stator winding consists of coils that are wound on all the poles of the machine. These are connected together forming a suitable series or parallel circuit on each phase winding. The terminal block has six main terminals for connecting the incoming power supply cables which are marked in accordance with IEC 60034-8. Stator winding connections are assigned with the notation U1-V1-W1 and U2-V2-W2. An e-motor terminal is shown in Figure 9.1. The leads connecting the windings to the motor terminals often have a colour coding system, each phase winding is represented by a different colour, eg black-red-white, as illustrated in Figure 9.2. Figure 9.1– Motor terminal block Figure 9.2 – Leads’ colour coding system A single speed three-phase induction motor winding can be connected in either star or delta from the side of the terminal. As seen in Figure 9.3, the configuration can be determined by the position of the terminal link: •In a star configured motor, links are fitted as in Figure 9.3a and power cable (L1, L2, L3) is connected to U1, V1 and W1; •in a delta configured motor, links are fitted as in Figure 9.3b and power cable (L1, L2, L3) is connected to U1, V1 and W1 again. To change the direction of a three-phase motor (star or delta), swap any two of the incoming power cables L1-L2-L3, and reconnect. a) b) Figure 9.3 – a) Induction motor star configuration b) Delta configuration In two-speed motors the terminal identification is different. Figure 9.4 illustrates a three-phase, two- speed motor. The terminals 1U, 1V, 1W relate to the slow-speed winding set and terminals 2U, 2V, 2W relate to the higher speed winding set. a) 62 • Ships’ Automation Available from: http://www.witherbyseamanship.com/ b) Figure 9.4 – (a) Delta-double star double pole motor winding (b) Motor terminal’s overview Large electric motors designed for external use may have integrated space heaters and thermistors. The terminals are visible inside the connection box. In the three-phase Delta-double star multi- pole induction motor used for two speed starter applications, Figure 9.4b, small terminals which are seen on top of the main terminals are integrated PTC sensor connections and space heaters. Figure 9.5 – WEG 3 kW motor nameplate In addition to identification, a motor’s nameplate indicates the features of the winding configuration, supplied voltage, power capacity, nominal current, rpm, power factor (cosf) and Indress Protection class (IP), see Figure 9.5. 9.3 Checking Stator Winding Before fault finding, ensure the motor is isolated from the main power supply by shutting off the MSP and control circuit power supply. Prior to making continuity checks to motor stator windings, ensure the terminal links are removed. The windings U1-U2, V1-V2, W1-W2 should be checked for continuity using a multimeter. All three of the measured values should be identical. A significant difference in the measured resistance values through the windings indicate a fault. Insulation checks Insulation checks are a vital part of the fault finding procedure (Figure 9.7). It is a non-destructive method of ensuring the effective insulation between the winding conductors. A suitable test voltage is applied using a 500 V or 1000 V insulation tester. A precondition for megger testing is that the motor is completely isolated from the supply and locking the switching devices off according to standard safety procedures. Figure 9.7 – Megger testing winding set U1-U2 To check the insulation resistance of the stator winding, measure the insulation resistance value Figure 9.6 – Measuring continuity for a winding set 63Available from: http://www.witherbyseamanship.com/ between each winding set (U-V-W) and earth with megohmmeter, as shown in Figure 9.7. A low reading may indicate an insulation failure of a winding ins ide the motor. The resistance value is measured in Mega Ohms (MO). If the insulation is less than or equal to 1 Mega Ohm for any of the winding phase sets, further investigation is required. The Classification Society’s requirements for megger testing must be adhered to in all routine work. For example, Germanischer Lloyd does not accept insulation values of less than 1 MO for voltages below 1000 V. Routine testing of all motors should be carried out and recorded at least quarterly, in accordance with classification requirements. Figure 9.7 illustrates an insulation test for winding set U1-U2. Similar measurements should be carried out for winding sets V1-V2 and W1-W2. Insulation checks should also be carried out between the two windings by checking the megger reading between the two different stator winding sets (U-V, U-W, V-W). Once all the tests have been completed, if there are no burnt or visually damaged parts and no physical obstructions to the motor turning shaft, a three- phase voltage can be applied to the motor starter, and the motor can be tested. A further check can be carried out by starting the motor, then measuring the phase current integrity using a clamp-meter. Clamp-meters, also called clip on meters, are operated by passing a conductor through the probe, as shown in Figure 9.8. It is important that only one conductor is measured. Figure 9.8 – Measuring phase L1 current with a clamp-meter 9.4 Phase Current Tolerance When the motor is running and the highest current reading of the three legs (measured with a clamp- meter) is below the nameplate Full Load Rating, it is safe to operate. If one leg reads in excess of the nameplate rating, but is within the amperage rated value, the motor is safe to operate. While small amounts of imbalanced loads are tolerated, excessively imbalanced currents can shorten a motor’s life and cause a subsequent increase in energy consumption. A current test on phase L1 is shown in Figure 9.8. Example: Motor Nameplate FLA (Full Load Amperage) = 10.0 Amps Measured with Clamp-meter: L1 = 9.8 Amps L2 = 10.6 Amps L3 = 10.2 Amps To determine the average: (9.8 +10.6 + 10.2)/3 = 10.2 Amps Determine the percentage difference as: (Highest Phase – Average)/Average × 100: = (10.6 – 10.2)/10.2 × 100 = (0.4/10.2) × 100 = 0.039 × 100 = 3.9% 9.5 Verifying e-motor windings If markings for the three windings were not identified before work was undertaken on a three- phase induction e-motor, it is essential that they are confirmed before the motor is reconnected. To do this, first verify the integrity of each of the three windings by measuring continuity, as illustrated in Figure 9.9a. Then, any two ends should be connected (Figure 9.9b) and a reduced voltage applied (24-110 V AC) across the other ends. An induced voltage will only be detected in the third winding if they are connected in series either end-to-beginning or beginning-to-end. It does not matter which end of the conductor is considered the beginning or end, only that they are identified in relation to the other windings. Two conductors can be marked as U1, U2, V1 and V2. Then, stop the power supply and connect the third windings to one that has been previously marked. Figure 9.9c shows the third winding connected with the second (marked as V1-V2), but in this example it has been set the wrong way. Therefore, when the power supply is applied across U1-U2, no voltage is induced. As a consequence, the third winding’s conductors should be marked the opposite way round. By following this process, the three beginnings U1, VI, Wl and three ends U2, V2, W2 are identified. Therefore this sequence is to be followed when connecting leads to motor terminal block. 64 • Ships’ Automation Available from: http://www.witherbyseamanship.com/ a) b) c) Figure 9.9 – Verifying e-motor winding, beginnings and ends