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Note: this updated article for the Induction Motor Speed Controller incorporates all the changes to the original version (including the modified PCB), as described in the December 2012 and August 2013 issues. The software is also revised. 1.5kW Induction Motor Speed Controller, Pt.2 Pt.2: by ANDREW ANDREW LEVIDO Last month, we described the features of the 1.5kW Induction Motor Speed Controller and explained in detail how it works. This month we describe its construction and testing and give some guidelines for use. WARNING: DANGEROUS VOLTAGES This circuit is directly connected to the 230VAC mains. As such, most of the parts and wiring operate at mains potential and there are also sections running at 325-350V DC. Contact with any part of these non-isolated circuit sections could prove FATAL. Note also that the circuit can remain potentially lethal even after the 230VAC mains supply has been disconnected! To ensure safety, this circuit MUST NOT be operated unless it is fully enclosed in a plastic case. Do not connect this device to the mains with the lid of the case removed. DO NOT TOUCH any part of the circuit unless the power cord is unplugged from the mains socket, the on-board neon indicator has extinguished and at least three minutes have elapsed since power was removed (and the voltage across the 470μ 470μF 400V capacitors has been checked with a multimeter – see text in Pt.1). This is not a project for the inexperienced. Do not attempt to build it unless you understand what you are doing and are experienced working with high-voltage circuits. 68  Silicon Chip siliconchip.com.au NYLON CABLE TIES 1 0 nF∗ S UP SLE PRESSIO EVE N CON5 RITE CON4 NYLON CABLE TIES V 220nF X2 NYLON SCREW WITH TWO LOCK NUTS NYLON CABLE TIES BOX FRONT PANEL (INSIDE VIEW) 150k NE-2 NEON WARNING! Neutral Earth Active 4004 4004 4004 4004 EARTH CON3 (COVERED) 150k 47nF X2 BR1 GBJ3508 (UNDER) DANGEROUS VOLTAGES W CON2 47nF X2 FUSE1 10A NYLON CABLE CLAMP 620k 16k IC1 STGIPS20K60 (UNDER) FLT1 YF10T6 CABLE GLAND (REAR VIEW) 620k TH1 SL32 10015 MINI MUFFIN FAN 8.2k 1 ORIENTATE FAN SO THAT IT BLOW S AIR INTO THE C ASE – SEE TEXT 8.2k 8.2k D1 D2 D3 D4 ∗ PART VALUES MARKED IN RED ON PCB HAVE BEEN CHANGED FROM ORIGINAL VALUES – SEE TEXT 8.2k 0.015Ω 2W SECURE FAN USING 4 x 20MM NYLON M3 SCREWS, NUTS & SHAKEPROOF WASHERS CON6 ZD2 RAMP SPEED FER 100nF 100nF VR1 VR2 10k 100nF 10k U 1.5k 100Ω∗ 100nF OPTO2 470 µF (GPO MAINS OUTLET MOUNTED ON OUTER SURFACE) ZD1 HCPL2531 OPTO3 10 µF BC337 Q1 100nF 100nF 100nF 100nF IC3 HCPL2531 10µF 100nF 10µF dsPIC33FJ64MC802 10 µF OPTO1 4N35 + HEATSHRINK SLEEVING A A Rev Run Fault A PP Ext O/S Flt TO TH2 CON7 470 µF LM317T 470 µF 100nF 100nF REG1 D5 D6 D7 D8 ISOLATION BARRIER T2 6V+6V 5VA (UNDER) + 4004 + 10k 1M ∗ 470Ω∗ 0.5W 4004 10µF 5.1V IC2 LM319 10Ω 4004 100nF 100nF 100Ω 4004 470 µF 400V (UNDER) ISOLATION BARRIER 100Ω 470 µF 400V (UNDER) 47k 470Ω 100Ω 470 µF 400V (UNDER) +3.3V 100Ω 100Ω T1 6V+6V 5VA (UNDER) Vin 100Ω 4.7k 5W 4.7k 100Ω 4004 4.7k 5W GND 1.5k 15V 180Ω D9 110Ω S1 – 4 4.7k 5W RUN 680Ω 10105122 100Ω 4.7k REV 100nF 100Ω + EST 5 + GND ICSP 1.5kW Induction Motor Speed Controller 100Ω 1 + + WARNING: ALL PARTS IN YELLOW AREA ON PCB OPERATE AT LETHAL VOLTAGE & LETHAL VOLTAGES REMAIN FOR SOME TIME AFTER POWER IS REMOVED – SEE TEXT Fig.8: follow this diagram to build the unit. Note that transformers T1 & T2, the three 470μF 400V electrolytic capacitors, bridge rectifier BR1 and IC1 (the IGBT module) are mounted on the underside of the board. B EFORE GOING any further, we must again remind readers that this project is intended only for experienced constructors. Most of the circuit operates at 230VAC mains potential and it has portions operating at 325350V DC. Furthermore, the circuit can siliconchip.com.au remain potentially lethal even after the 230VAC mains has been removed. Construction begins with assembly of the PCB. Be sure to use the revised PCB which is coded 10105122. Note that several component values were changed after this board was de- signed, so the screened overlay on early versions of this revised board may show the old values. The parts layout of Fig.8 is correct. Be sure also to use a PIC micro that’s programmed with the latest veresion of the software; ie, 1010512B.hex. May 2012  69 200 25 5 60 85 105 45 170 ALL NINE HOLES ARE TAPPED M3 70  Silicon Chip Fig.9: this full-size diagram shows the drilling details for the heatsink. It should be copied, attached to the heatsink with sticky tape and used as a drilling template. Use a small pilot drill (eg, 1mm) to start the holes, then drill each one to a depth of about 8mm using a 2.5mm drill. The holes are then tapped to 3mm. Use plenty of light machine oil to lubricate both the drills and the tap during this procedure and withdraw these parts frequently from the hole being worked on to clear any metal swarf (if this is not done, the aluminium swarf will bind to the tool and spoil both the tool and the job). Note: the drilling diagram is also available in PDF format from the SILICON CHIP website. 5 5 75 65 ALL DIMENSIONS IN MILLIMETRES TH2 MOUNTING POSITION 5 Note that some components are mounted on the underside of the board and there are five surfacemount components to contend with. These surface-mount components are all passive (four 10μF capacitors in 2012/0805 packages and one 0.015Ω 2W resistor in a 6432/2512 package) and are easy to install using a conven- tional soldering iron with a small tip. Start by loading these SMT components, then move on to the rest of the components in reverse height order. Don’t install any of the parts that mount underneath the board at this stage. Note that the 4N35 opto-coupler is mounted the opposite way to the two HCPL2531s. The 4.7kΩ 5W resistors must be mounted 2-3mm proud of the PCB to ensure free airflow on all sides. The input surge-limiting NTC thermistor TH1 should be mounted such that there is about 15mm of bare lead exposed above the surface of the board. This serves two purposes: first, it prevents the solder joints from overheating, since this component runs quite hot at full load. And second, it allows the thermistor to be bent down parallel with the PCB so that it will fit inside the IP65 case and not foul the lid. This can be seen in the photograph on page 74. However, don’t bend the thermistor down at this stage because you need access to the screw hole for the bridge rectifier, BR1. The bridge rectifier must be secured to the heatsink and soldered to the PCB, before the thermistor is bent over. Next you can begin mounting the parts on the bottom of the board. Leave the IGBT driver and bridge rectifier off for now. The polarity of the large electrolytic capacitors must be correct – a mistake here would be disastrous (not to mention messy and dangerous). Heatsink assembly Drill and tap nine M3 holes in the machined surface of the heatsink as shown in Fig.9. Make sure the holes are carefully de-burred so that the heatsink surface is completely smooth. Next, use the PCB as a template to bend the leads of the bridge rectifier upwards so that the leads fit and the mounting hole is directly under the corresponding hole in the PCB. The next step is to mount thermistor TH2 on the heatsink with its leads twisted and poking upwards so that they can be later soldered directly to CON7’s pads. Before fitting the heatsink thermistor, smear a small amount of heatsink compound on the mounting lug and then attach it to the heatsink with an M3 x 6mm screw and lockwasher. Orientate the lug so that the thermistor wires run to the right – see Fig.10. Now apply a thin smear of heatsink compound on the mounting surfaces of the IGBT driver (IC1) and bridge rectifier (BR1). Insert them in their appropriate places in the circuit board (from the bottom) but don’t solder them yet. You can stop them from falling out when you turn the board upright by making a small bend in a couple of the leads. siliconchip.com.au This view shows the underside of the PCB. Note the aluminium brackets attached to either side of the heatsink. Case and wiring Since much of the printed circuit board is at lethal potential, it is essential that the speed controller be siliconchip.com.au M3 x 10mm SCREW WITH FLAT WASHER IGBT BRIDGE MODULE DIODE BRIDGE M3 x 6mm SCREW WITH STAR LOCKWASHER 2 x M3 x 10mm SCREWS WITH FLAT WASHERS 5 x M3 x 16mm SCREWS WITH STAR LOCKWASHERS & 9 mm METAL SPACERS PCB THERMISTOR TH2 TO CON7 THERMAL GREASE (HEATSINK) THERMAL GREASE NOTE: DIAGRAM NOT TO SCALE Mount the PCB assembly on the heatsink using M3 x 16mm screws, star lockwashers and 9mm spacers, as shown in Fig.10. Once the board is firmly screwed into place you can screw down the IGBT and diode bridges using M3 x 10mm screws. These screws are inserted through the holes in the PCB but the flat washers have to be manipulated into place under the board using tweezers. Alternatively, you could glue them in place on the devices with a drop of superglue before assembly. Tighten the screws carefully, making sure both devices are flat against the heatsink. Once everything is in place, solder the pins from the top, clipping off any excess very carefully. Finally, twist and feed the heatsink thermistor (TH2) wires up through the CON7 pads with a pair of tweezers and solder them on the top of the PCB. It doesn’t matter which lead goes to which pad. Keep these leads short, so that they cannot possibly short against high-voltage circuitry if they come adrift. That completes the assembly of the controller module. Fig.10: diode bridge BR1, the IGBT module (IC1) and the 10kΩ thermistor TH2 are mounted on the heatsink as shown here. The PCB is attached to the heatsink at five points on 9mm untapped spacers while the leads from the heatsink thermistor are fed up through the PCB’s CON7 pads and soldered. mounted in a fully enclosed case. Whatever case you choose, you must take care that the mains wiring is fully compliant with the relevant standards. If the case is metal, it must be securely earthed. Note that the Speed Controller dissipates around 28W at idle and over 50W at full power. So we recommend that you either use a vented case or drill a series of holes on one side and fit a fan on the other side. We’ll show how to do this with the specified case. Obviously, with vents, the IP65 case is not waterproof or dustproof but the unit will run much cooler (and therefore more reliably) with airflow. Note also that if a plastic case is used, May 2012  71 Parts List: Induction Motor Speed Controller 1 double-sided PCB, code 10105122, 200.5 x 125mm 1 front panel label (147 x 102mm) 1 diecast heatsink, 200 x 75 x 48mm (Jaycar HH8546, Altronics H0536) 1 IP65 ABS case, 250 x 200 x 130mm (Altronics H0364A) 1 IP68 cable gland to suit 4-8mm cable (Jaycar HP0724, Altronics H4313) 1 surface-mounting single mains (3pin) socket 1 10A mains lead 1 ferrite suppression bead, 28mm long, 15mm OD, 7mm ID (Jaycar LF1260, Altronics L4802A) 1 60mm 12V DC fan (Jaycar YX2505) 1 60mm fan grille (Jaycar YX2550) 2 6+6V 5VA PCB-mount trans­ formers (Altronics M7052A) 2 10kΩ mini horizontal trimpots (VR1, VR2) 2 PCB-mount 3AG fuse clips (F1) 1 10A 3AG fast-blow fuse (F1) 1 fuse cover for F1 1 SL32 10015 NTC thermistor (TH1) (Element14 1653459) 1 10kΩ NTC thermistor with mounting lug (TH2) (Altronics R4112) 1 YF10T6 mains filter (FLT1) (Jaycar MS4000) 1 NE-2 Neon lamp (Jaycar SL2690, Altronics S4010) 2 3-way PCB-mount terminal barriers, 8.25mm pitch (CON2, CON3) (Altronics P2102) 3 3-way terminal blocks, 5/5.08mm pitch (CON4-CON6) 1 4-way DIP switch (LK1-LK4) 1 5-way pin header, 2.54mm pitch (ICSP) 1 2-way pin header, 2.54mm pitch (CON7) 1 Nylon* P-clamp to suit 5mm cable 12 small cable ties there must be no metal screws protruding through to the outside since that would present a safety hazard. We assembled our controller into a plastic case measuring 200mm x 250mm x 95mm (Altronics H0363). As shown in the photos, the PCB/ heatsink assembly is installed inside the case using a pair of brackets cut from aluminium angle. These brackets are screwed to the heatsink using M3 x 10mm screws, nuts & shakeproof washers and secured to the short pillars in 72  Silicon Chip 1 Nylon* M4 x 15mm machine screw (to secure P-clamp) 3 Nylon* M4 nuts 2 M4 x 20mm machine screws & nuts 4 M4 shakeproof washers 4 M3 x 20mm machine screws 4 Nylon* M3 x 20mm screws (to secure fan) 4 Nylon* M3 nuts 5 M3 x 16mm machine screws 6 M3 x 10mm machine screws 5 M3 x 9mm untapped metal spacers 14 M3 star washers 3 M3 flat washers 8 M3 nuts 4 No.4 x 9mm self-tapping screws 1 250mm length mains-rated heavyduty green/yellow striped wire 1 200mm length mains-rated extraheavy-duty red wire 1 200mm length mains-rated extraheavy-duty dark-blue wire 1 200mm length mains-rated extraheavy-duty white wire 1 300mm length 6-8mm diameter heatshrink tubing 1 300mm length aluminium L-shaped extrusion, 20 x 10mm * Use genuine Nylon (polyamide) parts rather than clear plastic Semiconductors 1 STGIPS20K60 3-phase IGBT bridge (IC1) (Mouser 511-STGIPS20K60, Digi-Key 497-10573-5-ND) 1 LM319 dual high-speed comparator (IC2) 1 dsPIC33FJ64MC802 16-bit microcontroller (Element14 1576842) programmed with 1010512B.HEX (IC3) 1 4N35 optocoupler (OPTO1) (Altronics Z1647) the base of the enclosure using No.4 x 9mm self-tapping screws. Mounting the fan Before installing the PCB, drill four mounting holes in the front side panel of the case for the fan and grille. The fan goes right in the middle of the panel and must be orientated so that it blows air into the case. The airflow direction is indicated with arrows moulded into the plastic housing. When drilling the holes, make sure 2 HCPL2531 high-speed dual optocouplers (OPTO2, OPTO3) (Element14 1021247) 1 LM317T adjustable linear regulator (REG1) 1 3mm green LED (LED1) 1 3mm yellow LED (LED2) 1 3mm red LED (LED3) 1 BC337 NPN transistor (Q1) 1 5.1V 0.4W/1W zener diode (ZD1) 1 15V 1W zener diode (ZD2) 1 GBJ3508 35A SIL bridge rectifier (BR1) (Mouser 833-GBJ3508-BP, Digi-Key GBJ3508-BPMS-ND) 9 1N4004 1A diodes (D1-D9) Capacitors 3 470µF 400V snap-in electrolytic (Altronics R5448) 3 470µF 25V electrolytic 1 10µF 25V electrolytic 4 10µF 25V SMD ceramic [2012/0805] (Element14 1867958) 1 220nF X2 250VAC (22.5mm pitch) (Jaycar RG5238, Altronics R3127) 14 100nF monolithic ceramic 2 47nF X2 250VAC (15mm pitch) (Jaycar RG5234, Altronics R3117) 1 10nF MKT or ceramic Resistors (0.25W, 1%) 1 1MΩ 2 4.7kΩ 2 620kΩ 2 1.5kΩ 2 150kΩ 1 680Ω 1 47kΩ 2 470Ω 0.5W 1 16kΩ 1 180Ω 1 10kΩ 1 110Ω 4 8.2kΩ 11 100Ω 3 4.7kΩ 5W 5% 1 10Ω 1 0.015Ω 2W SMD resistor [6432/2512] (Element14 1100059, Digi-Key MCS3264R015FERCT-ND) Note: additional components are required for external motor run/speed/ direction control – see text and Fig.11. that the fan (when mounted internally) will sit all the way down against the bottom of the case (so that the lid will still fit). You can use the grille as a template to locate the four 3mm holes, one in each corner. You will also have to make a 50mm-diameter cutout in front of the blades, so that the fan can draw air into the case. While you’re making holes in the box, drill a row of 6mm holes along the bottom half of the case side panel opposite the fan (see photo), to allow siliconchip.com.au Note: early prototype PCB shown. This view shows how the PCB assembly is mounted on the heatsink. Be sure to mount the PCB in place and tighten BR1 and the IGBT module (IC1) down on the heatsink before soldering their leads. fresh air to be blown out of the box when the fan is running. The more holes you drill, the better the airflow will be (to a point) but a row of 15 should be adequate. If you are using a larger case than that specified, you may want to consider using a 230VAC 120mm fan instead, which will move substantially more air and thus provide extra cooling. Secure the fan and the matching grille (with filter) in place using four Nylon M3 x 20mm screws, nuts and shakeproof washers. Mains socket If fitting a standard mains socket for a single-phase motor, mark out the three hole positions to the right of the fan. You will need to rotate it about 45°, ie, with screw holes at upper-left and lower right. The screw holes are 4mm while the central hole needs to be large enough to comfortably fit four mains-rated wires through (about 12mm diameter) and should be smooth, ie, no jagged edges. Mount it using M4 x 20mm machine screws with shakeproof washers under each head and nut. The mains input cable enters via a gland to the left of the fan and is secured to the inside of the case with a Nylon P-clamp. Use a Nylon screw and nut to secure it (not metal) and fit a second Nylon nut to lock the first one into place, so that the P-clamp assembly cannot possibly come loose. Complete the mains wiring accord­ ing to Fig.8, taking care that everything is properly secured with cable ties. Note that, for a plastic case, the Earth lead from the mains cable goes direct to the Earth terminal on the mains socket (GPO). A separate earth lead is then run from the GPO to the Earth terminal on the PCB. Use green/yellow mains-rated cable for this connection. The ‘W’ and ‘U’ outputs from CON2 go to the Active and Neutral terminals of the GPO socket. Use red and blue mains-rated cable for these connections. Don’t forget the ferrite RF suppressor on these output leads. This Table 1: Resistor Colour Codes o o o o o o o o o o o o o o siliconchip.com.au o o No.   1   2   2   1   1   1   4   2   2   1   2   1   1 11   1 Value 1MΩ 620kΩ 150kΩ 47kΩ 16kΩ 10kΩ 8.2kΩ 4.7kΩ 1.5kΩ 680Ω 470Ω 180Ω 110Ω 100Ω 10Ω 4-Band Code (1%) brown black green brown blue red yellow brown brown green yellow brown yellow violet orange brown brown blue orange brown brown black orange brown grey red red brown yellow violet red brown brown green red brown blue grey brown brown yellow violet brown brown brown grey brown brown brown brown brown brown brown black brown brown brown black black brown helps reduce the RFI radiated from the motor cable. With the mains wiring in place, you can then wire up the fan. It runs off the unregulated input to REG1 (about 6-7V) and so will run quite slowly (and hence, quietly). DO NOT wire it across the 15V HOT rail as the insulation of the fan may not be adequate. Because they run adjacent to highvoltage circuity, sleeve the fan leads with a continuous length of 5mm dia­meter heat­shrink tubing. Route the fan power cable around the right-hand side of the board and solder the leads to the cathode of D6 (red) and anode of D7 (blue or black) – see Fig.8. Use the hole immediately to the right of CON7 and the lower-right corner mounting post as cable tie Table 2: Capacitor Codes Value 220nF 100nF 47nF 10nF µF Value IEC Code EIA Code 0.22µF 220n 224 0.1µF 100n 104 .047µF   47n 473 .01µF   10n 103 5-Band Code (1%) brown black black yellow brown blue red black orange brown brown green black orange brown yellow violet black red brown brown blue black red brown brown black black red brown grey red black brown brown yellow violet black brown brown brown green black brown brown blue grey black black brown yellow violet black black brown brown grey black black brown brown brown black black brown ay 2012  73 brown black black black M brown brown black black gold brown This is the view inside the prototype. If you are going to use external controls, then these should be mounted on the righthand side of the case well away from the mains outlet socket the high-voltage circuitry on the PCB – see panel overleaf. Note the row of ventilation holes towards the bottom of the rear panel. Use cable ties to secure the high-voltage leads, the fan wiring and the ferrite cylinder as shown. points to clamp the fan cable (enlarge the hole next to CON7 if necessary). This is most important as otherwise, the solder joints could break and the wire could easily float around inside the case and cause havoc. That done, attach additional cable ties to ensure that all the wiring is properly tied down so that even if one of the wires breaks or becomes disconnected from the PCB, it can’t make contact with something that it shouldn’t – see Fig.8 and the photos. In particular, note how the sleeved fan leads and the mains Earth wire to the GPO are tied to the mounting holes at the top rear of the fan. Finally, double check your work, especially the mains wiring. Testing To test the control electronics, take 74  Silicon Chip a short piece of hook-up wire and connect it between the RUN terminal and one of the GND terminals. Ensure that all the DIP switches are off (sliders to the left), and set both trimpots to about 50%. Do not connect a load at this stage. With the unit on the bench, apply power and observe the neon and LEDs (it’s a good idea to wear goggles in case there are any nasty surprises when power is first applied). The neon should come on almost immediately and the green LED should begin flashing, as the microcontroller ramps up the output frequency. After about 15 seconds, the flashing should stop and the green LED should remain lit. If this is the case, the micro is working fine. If there is a problem, switch off, unplug the unit from the mains socket and wait until the neon has fully extinguished. You should then wait a further three minutes and check the voltage across the 470μF 400V electrolytics to make sure the circuit is safe. You can then carefully inspect your work for errors. Avoid making any measurements or troubleshooting this circuit while it is live. Only the portion of the circuit in the bottom right hand corner of the board inside the marked isolation barrier is isolated. The rest is at 230VAC mains potential and is lethal. If you want to check the control circuitry more thoroughly, first check that the unit is disconnected from the mains and that the 400μF 400V electrolytics have discharged, then feed 3.3V from an external regulated power supply into terminals 1 and 3 of the control terminal block (ie, at CON4). You could also simultaneously feed siliconchip.com.au 15V from a second supply into the +15VHOT line (cathodes of D2 & D3) to check the control circuitry on the high-voltage side (the negative side of this supply can be connected to the anodes of D1 & D4). In fact we debugged this circuit in this manner, even adding a third supply at 60V DC feeding the DC bus and some 10W load resistors. This way you can check pretty much all of the circuitry in a safe manner. Using it Once you’ve made some basic checks, you are ready to put the controller to use. We will examine three likely use scenarios: pool pump power saving, driving a single-phase motor with external controls and driving a 3-phase motor. The first step is to ensure that your motor is suitable for use with a speed controller of this type – see last month’s article for full details. In summary, any induction motor with a centrifugal switch is NOT suitable. Check the name-plate to ensure the motor is rated for 230V or 240V and 1.5kW (2HP) or less. 3-phase motors should be rated for 230/400V or 240/415V operation and 1.5kW or less. Pool pump operation In this mode, the controller operates in stand-alone mode (ie, without exterFig.11 (right): this front panel label should be placed behind a Perspex window which is then affixed to the case lid using silicone adhesive. It can be downloaded in PDF format from the SILICON CHIP website. Check List Before switching on: (1) Check that the electrolytic capacitors are all correctly orientated. (2) Check that the mains wiring and the output wiring from CON2 to the GPO are correct and securely laced. (3) Check that the heatsink is correctly earthed (ie, use a multimeter to check for continuity between the heatsink surface and the Earth pin of the mains plug). Make sure that the Earth screw to the left of CON3 is tight and siliconchip.com.au has a shakeproof washer fitted under its head. A row of ventilation holes must be drilled across the lower section of the rear panel (22-23mm up from the bottom) to allow the air sucked in by the fan to be blown out of the case. These holes should be about 6mm diameter. nal controls) and is connected to the output of the pool pump timer switch. When the pump is switched on, it ramps up to full speed, then runs the pump at full speed for 30 seconds, before ramping the pump down to a lower speed for the rest of the filtration period. When the timer switch disconnects the mains, the pump coasts to a stop, ready for the next cycle. This was explained in more detail in the previous article. To achieve this, the controller is configured as shown in Fig.11(A). The RUN terminal is hardwired to GND, so that the motor will automatically start, and the DIP switch for pool pump (PP) mode is set to ON. The speed pot should be set for about 70% of full speed, which gives a good compromise between efficient filtration and power saving. You may need to experiment with this setting. The ramp speed is not critical – about 25% of rotation seems to work quite well. Tool spin-up mode This is a variation on pool pump mode, where the motor spends less SILICON CHIP 1.5kW Induction Motor Speed Controller (1) Suitable for use with delta-connected 3-phase induction motors and single-phase induction motors without a centrifugal switch (2) Maximum Motor Rating: 1.5kW (3) Maximum Mains Current: 8.7A RMS (230V) (4) Prolonged low speed operation reduces fan cooling and may overheat the motor WARNING DANGEROUS VOLTAGES INSIDE DURING OPERATION & FOR SOME TIME AFTER POWER IS REMOVED May 2012  75 PP DIP SWITCH SETTINGS A W V (A) POOL PUMP 'STAND ALONE' MODE A W V FLT RUN R* EARTH O/S SPEED RAMP U NEUTRAL MOTOR ACTIVE EXT GND E RUN N PP DIP SWITCH SETTINGS * SELECT VALUE OF RESISTOR (R) IN SERIES WITH SPEED POT TO SET THE MINIMUM SPEED time at full power before dropping to the set speed (half a second rather than 30s). This feature can be useful for lathes or other equipment which start off-load and is activated with Pool Pump enabled and a shorting block across pins 3 & 4 of the ICSP header. Single-phase motor with external control LINK MOTOR ACTIVE FLT SPEED RAMP U NEUTRAL EARTH O/S GND E RUN N EXT SPEED (10kΩ) (B) SINGLE-PHASE EXTERNAL MODE In this example, we want to run a single-phase motor with external controls. Fig.11(B) shows how it’s wired. The speed is controlled using an external 10kΩ pot. The EXT DIP switch must be set to ON, to tell the micro to read the external pot instead of the onboard trimpot. In this case, we want to be able to run the motor at higher than rated speed, so the O/S (overspeed) DIP switch is also set to ON. Resistor R sets the minimum speed. Now when the RUN switch is clos­ ed, the motor will ramp up to the speed setting of the external pot. When the RUN switch is opened, the motor will ramp down to zero. The speed control pot and the RUN switch must be mounted on the side of the case near the isolated area. 3-phase motor operation * SELECT VALUE OF RESISTOR (R) IN SERIES WITH SPEED POT TO SET THE MINIMUM SPEED W V U R* EARTH FLT SPEED RAMP NEUTRAL MOTOR ACTIVE EXT O/S GND A REV E RUN N PP DIP SWITCH SETTINGS SPEED (10kΩ) RUN REV (C) 3-PHASE EXTERNAL MODE Fig.11: these diagrams show how to use the controller in pool pump mode (A), in single-phase mode with external controls (B) and in 3-phase mode with external controls (C). Safely Installing External Control Wiring The wiring to any external front-panel controls (ie, speed pot & switches) must be run using 230VAC-rated cable. This wiring must not be longer than necessary to reach the controls and must be securely terminated at both ends and laced together and to fixed tie points using cable ties. This will ensure that the leads cannot possibly come adrift and contact the motor output terminals or any other high-voltage circuitry outside the isolation barrier. Provided you do this, the external controls are electrically isolated from the high-voltage components and are safe. The controls themselves must be mounted on the righthand side of the case near the isolated area, well away from any high-voltage components. The controls should all be sleeved with heatshrink insulation and properly secured in place. 76  Silicon Chip The final example (Fig.11(C)) is for a 3-phase motor with external controls. This is similar to the previous example. The motor must be wired for 230V operation in delta configuration. Any 3-phase wiring should be run by a licensed electrician. One of the big advantages of 3-phase motors is that they can be reversed electrically. In this example, a reverse switch is connected between the REV terminal and ground. If the reverse switch is opened or closed while the motor is running, it will ramp down to zero speed, pause for a short time and then ramp back up in the opposite direction. Extended low-speed caution Finally, we should warn against running any induction motor, singlephase or 3-phase, at low speeds for extended periods. Where fitted, the internal fan will be ineffective at low speed and so there is no cooling. In fact, larger motors designed for speed control often have separately powered cooling fans for this reason. However, these tend to be rated over 1.5kW and thus are not suitable for use SC with this speed controller. siliconchip.com.au