Guided By :- Kachhadiya Niranj B. Parthiv R. Bhatt S S.T.B.S. COLLEGE OF DIPLOMA ENGINEERING, SURAT.

Stepper Motors

3 What is a Stepper Motor? The stepper motor is a motor which takes input pulses and then takes proportional steps to input these signals. You can use for positioning and/or speed control for most any applications. The stepper motor needs a power circuit and a sequence circuit for changing phase.

4 Sequencer Power Tr. CPU or Motion- Control-Chip Vm (Motor Power) Vcc (Logic power)

5 What is a Stepper Motor? Medical: Infusion Pump, Brad Test, X-ray, Dialysis, DNA Extraction, Pump Semiconductor: Masking, Etching, Wafer Handling, Test-equipment, Die-Bonder FA: Pick & Place, NC Machine, X-Y-Z stage OA: Printer, Fax, Scanner HA: HVAC, Cleaner Robot Other: Vending machine

6 Stepper and Synchronous Motors Movement Generation Movement Generation Step Mode Reduced Duty Cycle Synchronous Motor

7 NS N S S N NS S N S N SN S N S N SN N S S N NS N S S N NS S N S N SN S N S N  for the next step invert magnetic field in the other coil  one step  invert magnetic field in 1 coil  rotor follows the stator field Movement Generation SN N S S N  A stepper motor always needs electronic control.  step angle depends on number of poles -> fixed by construction  rotor follows the stator field

8 Movement Generation Tin Can Motor

9 N S N S N S N S N S N S N S N S N S N S N S N S N S N S N S N S Movement Generation Tin Can Motor - Step Generation N N NN S S S S S S SS N N N N front side teeth back side teeth if there is only 1 magnetic system... N S N S N S N S N S N S N S N S N S N S N S N S N N NN S S S S S S SS N N N N N N NN S S S S S S SS N N N N N S N S N S N S N S N S N S N S N S N S N S N S N S N S N S N S motor is able to start in both directions  direction is undefined 

10 N N NN S S S S Movement Generation Tin Can Motor - Step Generation 2 magnetic systems = 2 stators... electrical phase shift 90 °  direction is defined by coil control sequencing  coil 1 coil 2 coil 1 coil 2 direction CW direction CCW control pattern (bipolar motor): N S N S N S N S N N N N S S S S S S SS N N N N N S N S N S N S S S S S N N N N N S N S N S N S N N NN S S S S N S N S N S N S S S SS N N N N N S N S N S N S N N N N S S S S N S N S N S N S N N NN S S S S N S N S N S N S S S S S N N N N N S N S N S N S front side teeth back side teeth stator 1 stator 2

11 Old Technology, No Longer Used Movement Generation VR - Step Generation

12 SN S N S N  Rotor follows the stator field  Rotor reaches the end stop  noise  Rotor is not able to follow the stator field  Rotor swings back Movement Generation Step Loss SN N S S N NS N S S N NS S N S N SN S N S N SN N S S N NS N S S N NS S N S N SN S N S N SN N S S N  Motor will always loose n·4 steps

13 Stepper and Synchronous Motors Movement Generation Step Mode Reduced Duty Cycle Synchronous Motor

14 Step Mode Full Step Mode Step angle = catalogue value NS N S S N NS S N S N SN S N S N SN N S S N NS N S S N NS S N S N SN S N S N SN N S S N 0 1 I 1 / I 1max I 2 / I 2max 1 0 coil current in a bipolar motor

15 Step Mode Half Step Mode Step angle = half catalogue value NS N S S N NS S N NS S N S N S N S N SN S N S N SN S N SN N S S N N S S N 0 1 I 1 / I 1max I 2 / I 2max 1 0 coil current in a bipolar motor

16 Step Mode Half Step vs. Compensated Half Step 0 1 I 1 / I 1max I 2 / I 2max I 1 / I 1max I 2 / I 2max 1 0 1/  2 -1/  2

17 Stepper and Synchronous Motors Movement Generation Step Mode Reduced Duty Cycle Synchronous Motor

18 higher output power requires higher input power -> power losses increase -> duty cycle needs to be reduced, otherwise motor becomes too hot Reduced Duty Cycle Order a Motor with reduced duty cycle, specify cycle time, do not only request reduced coil resistance.  Otherwise you get a motor with reduced coil resistance. But the winding is changed so that it will have the same maximum power dissipation, same duty cycle and therefore the same output torque.Otherwise you get a motor with reduced coil resistance. But the winding is changed so that it will have the same maximum power dissipation, same duty cycle and therefore the same output torque. “We need more torque!“ M...torque ...angular velocity = M...torque P = M ·  · [Nm · rad/s]  You need more output power. higher output power requires higher input power -> power losses increase -> duty cycle needs to be reduced, otherwise motor becomes too hot “We need more torque!“

19 Stepper and Synchronous Motors Movement Generation Step Mode Reduced Duty Cycle Synchronous Motor

20 Synchronous Motor Schematic U~ Parallel Connection Common, full voltage over both coils Serial Connection otherwise too many windings with too thin wire -> not possible electrical phase shift is done by capacitor instead construction is similar to bipolar stepper motor construction is similar to bipolar stepper motor stepper motorsDC stepper motors are used with DC synchronous motorsAC synchronous motors are used with AC

21 Synchronous Motor Frequencies clock i1i1 i2i2 i1i1 i2i2 t t t t t bipolar stepper motor f = 200Hz synchronous motor f = 50Hz Speed is equal ! f = step frequency = f s f = frequency of coil current = f i f s = 4·f i (for motors with identical construction) f s = 4·f i (for motors with identical construction)

COCLUSION :- By this Presentation we can study about Stepper Motor & observe its working, Advantages and Applications. 22

23 THANK YOU