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1/31/2017 Starting Review Starting Review Starting at Full Power is called what: Wait for it…. Starting at Full Power is called what: “Across The Line” Starting This can cause inrush currents of how much? This can cause inrush currents of how much? 5-8 times the FLC (Full-Load Rated Current) Simple Reduced Current Simple Reduced Current • Starting at reduced power is called: • Starting at reduced power is called: “Soft Start: • Simplest methods using other Electrical components: • Simplest methods using other Electrical components: Resistive or Inductive Reduced Voltage Reduced Voltage • Reduced Voltage accomplished through: • Reduced Voltage accomplished through: Autotransformer • This is usually connected in what configuration? • This is usually connected in what configuration? Open Delta 1 1/31/2017 3-Phase starting method 3-Phase starting method • What method reduces starting power by 3 times through how the motor coils are connected? • What method reduces starting power by 3 times through how the motor coils are connected? Wye-Delta Starting • 2 Conditions necessary: 1) Must have access to all of the motor Leads 2) Motor must be designed to allow it • 2 Conditions necessary: Transitions Transitions • What can happen if the motor runs free for even a short time while starting? • What can happen if the motor runs free for even a short time while starting? The Rotor can induce high voltages in the Stator windings that will clash with the system voltage when it is switched back in. • How is this problem eliminated? “Closed Transitioning” in whcich the motor is never disconnecting the power during starting • How is this problem eliminated? Objectives CHAPTER 27 Part Winding Starters • Describe the construction of a motor designed to be used for a part winding starter. • Discuss three step starting for part winding motors. • Draw a control circuit for a part winding starter. • Connect a motor for a part winding starter. 2 1/31/2017 Part Winding Starters The Motor (Contains 2 windings) • The motor – Motors designed for part winding starting contain two sets of stator windings. – The stator windings and can be either wye or delta depending on the manufacturer of the motor. – The windings are designed to be connected in parallel with each other. – When the motor is started, only one winding is connected to the source. After a preset time, both windings are connected to the source at full voltage. Overload Protection Part Winding Starter Control Circuit With Overload Protection • Each winding is protected individually by means of overload heaters. • Each set of heaters (three per set) must be sized at one half the motor nameplate current. • The overload contacts from each relay are connected in series. Dual Voltage Motors used as PW • Some, but not all, dual voltage motors may be used for part winding starting. Contact motor manufacturer before an attempt is made. • If this is possible the motor must be operated on the low voltage connection. • Delta connected dual-voltage motors cannot be used for part winding starting. Each set of windings has OL Heaters set for ½ rated Current Both OL NC Contacts in series Dual Voltage Motors • Dual voltage connection used for part winding starting – This will only work for WyeConnected Motors 3 1/31/2017 Using a Dual V Motor for Part Winding Start 1) Contact Manufacturer 2) Must be connected for Low Voltage 3) Must be in Y Configuration Three-step Starting 1) Resistive, Part Winding start 2) Full Voltage on Part Winding 3) Full Voltage to Both Windings • A Watchdog Timer (TR2) disconnects the motor if the second winding does not energize. Motor Application • Part winding starting typically used for motors that supply centrifugal pumps, fans, and blowers • Often used in commercial air conditioning and refrigeration applications • Not for starting heavy inertia loads that require excessive starting time Automatic Shutdown • The part winding motor is very sensitive to the amount of time the start winding can be energized without the run winding becoming energized. • If the start winding is energized too long without the run winding, it can become severely damaged. • #5, Start pressed, nothing happens, no clicks, no motor bumps… Where would you first look for the problem? • Note, this is a “NOT” problem where three of the 4 options COULD be the problem. 4 1/31/2017 • #6 Start Pressed, CR energizes and opens after 4 seconds. Motor never moves. A failure in what rungs would cause this? • … • #5, Start pressed, nothing happens, no clicks, no motor bumps… Where would you first look for the problem? • If Nothing happens look to the beginning: Transformer, Fuse, First rung… • #6 Start Pressed, CR Summary energizes and opens after 4 seconds. Motor never moves. A failure in what rungs would cause this? • In this chapter, we discussed: • CR Energizes so Rung 1 is good. • Motor does not start, and M1 causes the rest of the sequence so… – The construction of a motor designed to be used for a part winding starter – Three-step starting for part winding motors – The control circuit for a part winding starter – How to connect a motor for a part winding starter ROLL CALL 5