Three Phase Motors Topic 3 Connecting and Starting

Three Phase Motors Topic 3: Connecting and Starting Three Phase Induction Motors All copyright and intellectual property rights in respect of materials developed by the service provider during this project will vest in the Department of Higher Education and Training, which will have the right to allow any individual, company, agency or organisation to use or modify the materials for any purpose approved by this Department, including selling the materials or releasing them as Open Educational Resources (OER) under an appropriate copyright license.

Assumed prior learning 05_01_00 05_01_02 05_02_01

Outcomes By the end of this unit the learner will:

Unit 3. 5: Automatic Three Phase Sequence Starter

Introduction In the previous unit, we found a way to make sure that motors start and stop only in a defined sequence. But starting and stopping the motors was still a manual process. In this unit we are going to learn how to use timers to start and stop motors automatically after predefined amounts of time.

Safety first When you work with motors you must put your safety and the safety of others first. You must complete the necessary Hazard Identification and Control (HIAC) Form. Need help with HIACs? Click the button to go to Topic X in The World of an Electrician Get help with HIAC Forms

Before We Begin Before you do any work on a motor, you must make sure that you have isolated and locked out the supply to the motor. Make sure you know how to do this by referring to Topic X in The World of An Electrician. Learn about Isolating and Lock-Out Procedures

When time is important Think about this. A large industrial fan is spinning in one direction. What would happen if we reversed the motor’s direction without letting the fan slow down first? a) Nothing b) We would put the motor under strain c) The motor might burn out d) The fan would spin in the opposite direction straight away.

Is there a solution? In this scenario, we cannot just reverse the motor. We need a way to make sure that the blades have slowed down enough before the motor can be started in the reverse direction. We can use a timer for this.

What is a timer? Timers or time-delay relays are special components that allow us to control when specific events happen in our motor circuits. Like contactors, they have a coil and NO and NC contacts. There are 2 main types. Click each box to find out more. 1 ON Delay The contacts change state a set time after the coil is energised. 2 OFF Delay The contacts change state a set time after the coil is de-energised.

ON delay timers Here is an ON Delay timer with a NO and a NC contact. Let’s see how it works. Set the timer and then energise and de-energise the coil to see what happens to the contacts. Set Time 3 s Energise coil 3 s NC ON Delay contact NO ON Delay contact

OFF delay timers Here is an OFF Delay timer with a NO and a NC contact. Let’s see how it works. Set the timer and energise and then de-energise the coil to see what happens to the contacts. Set Time 3 s Energise coil 3 s NC OFF Delay contact NO OFF Delay contact

How do you wire timers into circuits? We wire timers into control circuits just like contactors and relays. Watch the video to see how to wire ON and OFF Delays into control circuits and how to represent them in your diagrams. Img 05

A summary Here is a summary of 4 different types of timer contacts. Click on each box for more information. ON Delay OFF Delay NO Normally Open, NOTC Timed Close Normally Open, NOTO Timed Open NC Normally Closed, NCTO Timed Open Normally Closed, NCTC Timed Close

Normally Open, Timed Close (NOTC) This is an ON Delay contact. In this example… • the contact closes 5 seconds after the coil is energised • the contact opens immediately when the coil is de-energised

Normally Closed, Timed Open (NCTO) This is an ON Delay contact. In this example… • the contact opens 5 seconds after the coil is energised • the contact closes immediately when the coil is de-energised

Normally Open, Timed Open (NOTO) This is an OFF Delay contact. In this example… • The contact closes immediately when the coil is energised • The contact opens 5 seconds after the coil is de-energised

Normally Closed, Timed Close (NCTC) This is an OFF Delay contact. In this example… • The contact opens immediately when the coil is energised • The contact closes 5 seconds after the coil is de-energised

Review the basic reversing starter Back to our industrial fan. Let’s design a control circuit that will prevent the fan being reversed within 60 s of it being stopped. This should be enough time to allow the blades to stop spinning. Click on the image to remind yourself what the basic reversing starter control circuit looks like. Img 06

What sort of timer do we need? We want to make sure that the R circuit cannot be activated within 60 s of the F circuit being stopped. We also want to make sure that the F circuit cannot be activated within 60 s of the R circuit being stopped. Therefore, we need interlocks with NC contacts that will revert to being closed 60 s after their coils are de-energised i. e. a NCTC set to 60 s. Work out and draw the control circuit for this timed reversing starter.

How does our circuit compare? Were you able to design the control circuit for our situation? Have a look to see how your circuit compares with this one. Click on the image to see a full screen version of the control circuit. Img 06 a

How did you do? Did you manage to design the control circuit for this timed reversing starter. Compare your design with this one. Watch the video to see how to design the control circuit for scenario 3. Img 09

Wire it up Now, practice wiring this control circuit using the motor wiring simulator. Click on the image to access the motor wiring simulator. Img 07

Upload your control circuit diagram Draw your own copy of the timed reversing starter control circuit. Take a photo of your completed control circuit for the and upload it to your online portfolio. Choose image Upload

Ready to try design your own circuits? Put what you have learnt so far into practice by designing your own control circuits to meet the requirements of the following scenarios? Click on each box to open the scenario. 1 Scenario 1 2 Scenario 2

Sc en The conditions Work out and draw the control circuit for 2 motors for these conditions. Look at the hint if you need to. 1. Motor M 2 can only be started 10 seconds after motor M 1 is started. 2. The emergency stop button must stop both motors at all times. 3. When motor M 1 is stopped, motor M 2 must also stop. Hint ari o 1

Sc en Wire it up Now, test your scenario 1 control circuit by wiring it up using the motor wiring simulator. Click on the image to access the motor wiring simulator. Img 10 ari o 1

Sc en Upload your circuit diagram Take a photo of your completed control circuit for scenario 1 and upload it to your online portfolio. Choose image Upload ari o 1

Sc en How did you do? Did you manage to design the control circuit for scenario 1? Compare your design with this one. Watch the video to see how to design the control circuit for scenario 1. Img 12 ari o 1

The conditions Sc Work out and draw the control circuit for 3 motors for these conditions: 1. Motor M 2 starts automatically 10 s after motor M 1. 2. Motor M 3 starts automatically 10 s after motor M 2. 3. The emergency stop button must stop both motors at all times. 4. Motor M 1 cannot be restarted unless motors M 2 and M 3 are first stopped (with the emergency stop button). 5. An overload on any one motor must stop all the motors. en ari o 2

Sc en Wire it up Now, test your scenario 2 control circuit by wiring it up using the motor wiring simulator. Click on the image to access the motor wiring simulator. Img 13 ari o 2

Sc en Upload your control circuit diagram Take a photo of your completed control circuit for scenario 2 and upload it to your online portfolio. Choose image Upload ari o 2

Sc en How did you do? Did you manage to design the control circuit for scenario 2? Compare your design with this one. Watch the video to see how to design the control circuit for scenario 2. Img 14 ari o 2

Video Briefing – Vid 01 Video of an expert electrician showing how to wire ON and OFF delay timers into control circuits and how to represent them in diagrams (symbols, coils, contacts and time settings) 1. ON Delay 1. Show NCTO operation with light bulb – draw the circuit diagram 2. Show NOTC operation with light bulb – draw the circuit diagram 2. OFF Delay 1. Show NCTC operation with light bulb – draw the circuit diagram 2. Show NOTO operation with light bulb – draw the circuit diagram 3. Explain the working of each contact with the aid of diagrams like this…

OL E/S Image Briefing – Img 06 a -Stop(R) -K(F) -Start(F) -K(R) -K(F) -K(R) -T(F) -T(R) -K(R) -T(R) -K(F) -T(F)

Instructions 1. To add a wire between 2 points, click the starting connection and then click the ending connection. 2. To delete a wire, click on it and then click the Delete icon in the top right corner. 3. To change the colour of a wire, click on it and then click on the colour. 4. To move a component, click and drag it to a new position. Practice Connect the motor protection breaker circuit breaker up to the contactor L 1 T 1 L 2 L 3 T 2 T 3 MPCB L 1 T 1 L 2 Test L 3 A 1 Forward T 2 T 3 A 2 N O N C

Wire the 3 P timed sequence starter according to your control circuit diagram. L 1 Brea ker 1 T L 1 Brea ker 2 T L 2 L 3 Overload Relay T T T 1 2 3 L 1 L 2 L 3 A 1 Contactor. F T 1 T 2 Test F R ES Instructions 1 1 L 1 R W B T 3 A 2 N O N C A 1 N O N C A 1 OFF Delay. F A 2 N O OFF Delay. R N C A 2 L 1 L 2 L 3 A 1 T 2 T 3 A 2 Contactor. R N C N O N C Print

Wire the 3 P timed sequence starter according to your control circuit diagram. L 1 L 2 L 3 N O Overload Relay T T T 1 2 N O 3 F N C L 1 Brea ker 2 T 1 L 1 Brea ker T ES R 1 N C R Test L 1 L 2 L 3 A 1 T 2 T 3 A 2 Contactor. F F R W B A 1 N O N C L 1 OFF Delay. F A 1 L 3 Contactor. R T 1 N C L 2 A 1 T 2 N O T 3 A 2 N C OFF Delay. R N O N C Instructions Print

Video Briefing – Vid 02 Video of an expert electrician wiring up the timed reversing circuit 1. Start with the basic reversing control circuit and diagram and review what the interlocks are doing. 2. Wire in the 2 OFF delay timers. Explain why we need to use OFF delay timers and interlocks. 3. Connect the interlocking timer NCTC contacts 4. Test the circuit and notice that the NCTC contacts now also do the job of the main contactor NC contacts – we don’t need these. 5. Remove these from the circuit and test again 6. Draw the final control diagram (without interlocking main contactor NC contacts)

Instructions 1. To add a wire between 2 points, click the starting connection and then click the ending connection. 2. To delete a wire, click on it and then click the Delete icon in the top right corner. 3. To change the colour of a wire, click on it and then click on the colour. 4. To move a component, click and drag it to a new position. Practice Connect the motor protection breaker circuit breaker up to the contactor L 1 T 1 L 2 L 3 T 2 T 3 MPCB L 1 T 1 L 2 Test L 3 A 1 Forward T 2 T 3 A 2 N O N C

Wire the 3 P timed reversing starter according to your control circuit diagram. L 1 Brea ker 1 T Brea ker 2 T 1 L 1 Test 1 2 ES Instructions 1 L 2 L 3 Overload Relay 1 T T T 1 2 3 L 1 L 2 L 3 A 1 Contactor 1 T 1 R W B T 2 T 3 A 2 N O N C N O N O L 1 L 2 L 3 Overload Relay 2 T T T 1 2 3 L 1 L 2 L 3 A 1 Contactor 2 T 1 T 2 T 3 A 2 N O N C Print A 1 N O N C ON Delay A 2 N O N C

Wire the 3 P timed reversing starter according to your L control circuit diagram. 1 R W B Brea ker 1 T L 1 Brea ker 2 T ES 1 1 L 2 L 3 1 A 1 Contactor 1 T 1 L 1 T 2 L 2 T 3 L 3 Overload Relay 1 T T T 1 2 3 1 A 2 N O N O N O N C Test 2 2 L 1 L 2 Instructions A 1 L 3 Contactor 2 A 1 N O N C ON Delay A 2 N O N C T 1 T 2 T 3 A 2 L 1 L 2 N O N C L 3 Overload Print N O N C

Video Briefing – Vid 03 Video of an expert electrician wiring up the timed sequence circuit for scenario 1. 1. Start with the basic sequence circuit. 2. Wire in the timer and the interlocking NOTC contact to M 2 3. Wire in the NO interlocked contact to M 2 and explain how this will make sure that M 2 shots off when M 1 is stopped but that M 2 can be stopped independently.

Instructions 1. To add a wire between 2 points, click the starting connection and then click the ending connection. 2. To delete a wire, click on it and then click the Delete icon in the top right corner. 3. To change the colour of a wire, click on it and then click on the colour. 4. To move a component, click and drag it to a new position. Practice Connect the motor protection breaker circuit breaker up to the contactor L 1 T 1 L 2 L 3 T 2 T 3 MPCB L 1 T 1 L 2 Test L 3 A 1 Forward T 2 T 3 A 2 N O N C

Wire the 3 P timed reversing starter according to your control circuit diagram. L 1 Brea ker 1 T Brea ker 2 T 1 L 1 Test 1 1 ES Instructions 1 L 2 L 3 Overload Relay 1 T T T 1 2 3 L 1 L 2 L 3 A 1 Contactor 1 T 1 R W B T 2 T 3 A 2 N O N C N O N O L 1 L 2 L 3 Overload Relay 2 T T T 1 2 3 L 1 L 2 L 3 A 1 Contactor 2 T 1 T 2 T 3 A 2 N O N C L 1 L 2 L 3 Overload Relay 3 T T T 1 2 3 L 1 L 2 L 3 A 1 Contactor 3 T 1 T 2 T 3 A 2 N O N C Print A 1 N O N C ON Delay. A A 2 N O N C A 1 N O N C ON Delay. B A 2 N O N C

Wire the 3 P timed reversing starter according to your control circuit diagram. L R W B L 1 1 Brea ker 1 T 1 1 1 L 2 L 3 A 1 T 2 T 3 A 2 Contactor 1 A 1 N O N O N O N C L 1 L 2 L 3 Overload Relay 1 T T T L 1 L 2 L 3 A 1 Contactor 2 N C ON Delay. A A 2 N O T 1 A 1 N O T 2 N C ON Delay. B A 2 N O Brea ker 2 T ES N C T 3 A 2 N O N C 1 2 3 L 1 L 2 L 3 Overload Relay 2 T T T 1 L 1 2 L 2 3 L 3 Overload Relay 3 T T T 1 2 3 1 N O N C N O N C Test Instructions Print L 1 L 2 L 3 A 1 T 2 T 3 A 2 Contactor 3 N O N C

Video Briefing – Vid 04 Video of an expert electrician wiring up the timed sequence circuit or scenario 2. 1. Explain that we will need 2 NOTC contacts – one set for 10 s the other for 20 s 2. Start with the control circuit for M 1 and wire in the ON delay relays. 3. Then do M 2 and M 3 with their contactors and their interlocked NOTC contacts. 4. Then do the 3 OLs in series with the ES before any motor splits in the circuit 5. Then do the M 2 and M 3 interlocked NC contacts into M 1 circuit with –K(1) NO contact in parallel as a retaining contact for when M 2 and M 3 are running. 6. Make sure that the circuits is built, drawn and tested at each step.