Step motor characteristics and how©π to choose?
Date：May 17th,2023
With the increasing importance of↑λ✔ the control motor, the use of the contro× λl motor also increases year∞> by year. Stepper motor is a kin"✔∏d of control motor, withou☆↑↑t using the feedback loop, it can cε ★onduct the speed control and position'∏≥ing control, namely the so-called m≤∞••otor open loop control.
Its application is mainly based on OA machin ✘☆♣es and FA machines with stro>♠∞☆ng office business ability as the core, and i♦¶÷s widely used in medical devices, measuring inst ♦ruments, automobiles, game consol×♥es, etc. In terms of quantity, 0A machine applicaφπ∞tions account for about 75% of thΩ←§e total stepper motor use.
1. Principle of the stepping motor
Stepper motor is a motor that uses theσ'∞Ω principle of electromagnet to convert ¶δthe pulse signal into line displacement or angul←>→ar displacement. With each el☆÷≤εectric pulse, the motor rotates at an Angle, dr×★≈ive the machinery to move a short distan" ce.
2. classify
Motor has various classification, such as A• ¶±C drive and AC drive for voltage clas£σ ∏sification, and synchronous motor a≈αnd assynchronous motor.
The stepper motor is a synchronous motor driven ↔$↓→by DC, but it cannot be driven directly by DCπ↑£ or AC power supply. It needs to be equipped wit©≥÷h a driver to use it. So the operation of the ±♣stepping motor requires the drive circuit. T&ε₩his point is the same as thΩ✔α♦e brushless DC motor, the brushless DC motor to™≥λΩ use the drive circuit, the ¥σ£drive circuit will be the motor stator and thπ±e DC power supply connected to work togethe™¶€₽r.
3. Stepper motor characteristics ↔
The basic characteristics of the stepp∞®ing motor include motor static charact♠₹>>eristics, continuous motion characteristics (dyna↕₽mic characteristics), motor starting charact©§₽↕eristics and motor braking characteristics (tra♥¥>γnsient characteristics). The following are ∑↑→introduced respectively:
1. Static torque characteristics
When the coil of the steppinφλg motor is directly connected, ₽Ωthe relationship between the electromagneti₹ε↕±c torque with the load rotor (the recovery ↔•§electromagnetic torque generated by the loaδ∑d torque balance is called staλ tic torque or static torque) and the ro₩₽♥↓tor power angle is called the Angle-sta♣♣tic torque characteristic, which is the static&φ characteristic of the motor.
Because the rotor is a permanent magnet♣φ, the resulting magnetic air gap is sinusoidal ≠Ωdistribution, so theoretically the∑←•≥ static torque curve is sinuso★£idal wave. This Angle-static torque characteristi<✔↑∏c is an important indicator of the ability $βof the stepping motor to produce electrom£↔→agnetic torque. The greater the maximum toα✘rque, the better, and the closer the torque waveβπ £form is to the sine, the better. In↕π fact, there is a slot torque under thΩ↑e magnetic pole, which distorts the synthetic±$ torque. For example, the groove§• torque of the two-phase motor is 4 tiλ₹mes the harmonic period of the stationary torqu÷>☆←e, and added to the statio<" nary torque of the sine, the torque shown ¥ in the above figure is:
TL=TMsin[(θL/θ§≈>M)π/2]
The TL and TM each represent the lo♠×ad torque and the maximum static torque (oδ →±r hold torque), and the corresponding power angle₩ s are θ L and θ M. The change of th±←γis displacement angle determ>>Ω≥ines the position accuracy of >≤✔the stepper motor. According to the above equa©♦tion:
θL=(2θM/π)arcs↑✔in(TL/TM)
The step Angle of PM permanent γ♣magnet stepping motor and HB hybrid< &' stepping motor θ s was mentioned in the previous course: θ s=180 / PNrφ∏, the Angle is changed to mechanical An☆©↑gle (radian), then the followin★g formula:
θs=π/(2Nr)
The upper formula Nr is the number of rotor t✔≈eeth or the polar logarithm, so the two$✘™₽-phase motor θ M= θ s.
2. Dynamic torque characteristics
Dynamic torque characteristics includ₩>σβe drive pulse frequency-tor≈₹↕que characteristics and dr ®ive pulse frequency-inertia characteristics≠™.
1) Pulse frequency-torque ch™ aracteristics
Pulse frequency-torque characteristic is a©♣n important choice of steppin♥δg motor
Its application is mainly based on OA machin ✘☆♣es and FA machines with stro>♠∞☆ng office business ability as the core, and i♦¶÷s widely used in medical devices, measuring inst ♦ruments, automobiles, game consol×♥es, etc. In terms of quantity, 0A machine applicaφπ∞tions account for about 75% of thΩ←§e total stepper motor use.
1. Principle of the stepping motor
Stepper motor is a motor that uses theσ'∞Ω principle of electromagnet to convert ¶δthe pulse signal into line displacement or angul←>→ar displacement. With each el☆÷≤εectric pulse, the motor rotates at an Angle, dr×★≈ive the machinery to move a short distan" ce.
2. classify
Motor has various classification, such as A• ¶±C drive and AC drive for voltage clas£σ ∏sification, and synchronous motor a≈αnd assynchronous motor.
The stepper motor is a synchronous motor driven ↔$↓→by DC, but it cannot be driven directly by DCπ↑£ or AC power supply. It needs to be equipped wit©≥÷h a driver to use it. So the operation of the ±♣stepping motor requires the drive circuit. T&ε₩his point is the same as thΩ✔α♦e brushless DC motor, the brushless DC motor to™≥λΩ use the drive circuit, the ¥σ£drive circuit will be the motor stator and thπ±e DC power supply connected to work togethe™¶€₽r.
3. Stepper motor characteristics ↔
The basic characteristics of the stepp∞®ing motor include motor static charact♠₹>>eristics, continuous motion characteristics (dyna↕₽mic characteristics), motor starting charact©§₽↕eristics and motor braking characteristics (tra♥¥>γnsient characteristics). The following are ∑↑→introduced respectively:
1. Static torque characteristics
When the coil of the steppinφλg motor is directly connected, ₽Ωthe relationship between the electromagneti₹ε↕±c torque with the load rotor (the recovery ↔•§electromagnetic torque generated by the loaδ∑d torque balance is called staλ tic torque or static torque) and the ro₩₽♥↓tor power angle is called the Angle-sta♣♣tic torque characteristic, which is the static&φ characteristic of the motor.
Because the rotor is a permanent magnet♣φ, the resulting magnetic air gap is sinusoidal ≠Ωdistribution, so theoretically the∑←•≥ static torque curve is sinuso★£idal wave. This Angle-static torque characteristi<✔↑∏c is an important indicator of the ability $βof the stepping motor to produce electrom£↔→agnetic torque. The greater the maximum toα✘rque, the better, and the closer the torque waveβπ £form is to the sine, the better. In↕π fact, there is a slot torque under thΩ↑e magnetic pole, which distorts the synthetic±$ torque. For example, the groove§• torque of the two-phase motor is 4 tiλ₹mes the harmonic period of the stationary torqu÷>☆←e, and added to the statio<" nary torque of the sine, the torque shown ¥ in the above figure is:
TL=TMsin[(θL/θ§≈>M)π/2]
The TL and TM each represent the lo♠×ad torque and the maximum static torque (oδ →±r hold torque), and the corresponding power angle₩ s are θ L and θ M. The change of th±←γis displacement angle determ>>Ω≥ines the position accuracy of >≤✔the stepper motor. According to the above equa©♦tion:
θL=(2θM/π)arcs↑✔in(TL/TM)
The step Angle of PM permanent γ♣magnet stepping motor and HB hybrid< &' stepping motor θ s was mentioned in the previous course: θ s=180 / PNrφ∏, the Angle is changed to mechanical An☆©↑gle (radian), then the followin★g formula:
θs=π/(2Nr)
The upper formula Nr is the number of rotor t✔≈eeth or the polar logarithm, so the two$✘™₽-phase motor θ M= θ s.
2. Dynamic torque characteristics
Dynamic torque characteristics includ₩>σβe drive pulse frequency-tor≈₹↕que characteristics and dr ®ive pulse frequency-inertia characteristics≠™.
1) Pulse frequency-torque ch™ aracteristics
Pulse frequency-torque characteristic is a©♣n important choice of steppin♥δg motor