6-electric motor new(电机)

13 Is the speed of the rotor the same as the speed of RMF?
n ＜ n0
Passage 6
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14 what is slip? This speed difference is called the slip.
Passage 6
Electric motor 单击此处编辑母版标题样式
11 working Principle ? ★ Find the direction
N
of induced current in rotor winding by righthand rule. ★ Find the direction of electromagnetism force by left-hand rule. EM→EM torque T
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Electric motor 单击此处编辑母版标题样式
Passage 6
Electric motor 单击此处编辑母版标题样式
4 What is a stator?
Stator is composed of stator core and winding
Passage 6
Electric motor 单击此处编辑母版标题样式
U2
Each phase is composed of two series coils
U3
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10 What is pairs of poles?
p 1 2 n0/(r/min) 3000 1500 3 1000 4 750 5 600 6 500
Passage 6
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17 Three phase asynchronous motor. If the rotor circuit is open, will it be possible to generate the EM torque?
Passage 6
6 ways of connection?
U1 V1 W1 W1 U2 V2
U1 U2 V2 W2 W2
Wye
V1
W1
U1
V1
W1
U2
V2
W1
U2
V2
Star connection
Delta connection
Passage 6
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7 what is RMF?
Passage 6
Electric motor 单击此处编辑母版标题样式
3 what kind of motor is this?
Passage 6
Electric motor 单击此处编辑母版标题样式
3 List the main parts of asynchronous motors
stator, rotor, cover, base, shaft bearing, fan,etc.
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19 Cage asynchronous motor starting
(1) Direct starting 直接起动 (full-voltage starting 全压起动) Low-capacity motor 小容量的电动机 Below 7.5 kW, start directly. 7.5kW以下直接起动 Power supply capacity is large enough 电源容量足够大
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• 阅读教材492-495
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Electric motor 单击此处编辑母版标题样式
1 what is Electric motor?
Electric motor or electric machine is an electromagnetic device used to convert energy or signal.
Passage 6
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19 what are Mechanical characteristics?
n = f (T)
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19 what is the meaning of the nameplate?
terminals
UN = 380V 4. Rated current IN
IN = 7.2A 5. Rated power factorλN= cos N 6. Rated speed nN
→rated line current in stator
Passage 6
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rotating magnetic field
A rotating magnetic field is a magnetic field which changes direction at a constant angular rate. This is a key principle in the operation of the alternating-current motor.
Passage 6
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1.Type Y132S－6 2. Rated power PN
→2p = 6 →n0 = 1000 r/min
PN = 3kW
3. Rated voltage UN
→The rating mechanical output
→line voltage across the winding
Passage 6
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2 Classification :
(1) Power electric machine:动力电机
DC machine & AC machine
Separately excited Shunt excited Series excited Compound excited 他励电机 并励电机 串励电机 复励电机 Asynchronous 异步电机 Synchronous 同步电机
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(2) Control machine 控制电机 Servo motor：Convert voltage signal to angular displacement or velocity signal. 伺服电动机：电压信号转化为角位移或角速度。 Speed measure generator：Convert rotation speed to voltage. 测速发电机：将转速转化为电压信号。 Step motor：Electric impulse to turning angle or rotation speed. 步进电动机：电脉冲信号转化为转角或转速。 Rotation transformer：Turning angle to voltage. 旋转变压器：转角信号变换成电压信号。
5 List the major rotor types.
Rotor is sorted by structure
■ cage rotor
■ wire-wound rotor
Slip-ring rotor
Passage 6
Electric motor 单击此处编辑母版标题样式 U1 V1 W1
S
The direction of T is the same with n0
Passage 6
Electric motor 单击此处编辑母版标题样式
12. How to change the direction of rotor?
3~
3~
正 转
M 3~
M 3~
反 转
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T
2 ∝U1p
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16 Explain the power transfer.
Input active power: 输入的有功功率: P1 = 3 U1LI1L = 3 U1PI1P
Output mechanical power: P2 = T2 = 2 nT2 60 输出的机械功率: P2 = 100% Efficiency of motor: P1 电动机的效率: Power loss: 功率损耗: P = PCu＋PFe＋PMe P2 = P1－P
19 Starting characteristics of induction motor：
Starting current is high IS = KI IN =（5～7）IN • Starting torque is small TS =KSTN =（1.6～2.2）TN
Passage 6
Three-phase asynchronous motor
Type Y132S－6 Voltage 380 V Speed 960r/min Power 3 kW Frequency 50Hz Current 7.2 A Connection Y Power factor 0.76 Insulated class B
19 Three phase asynchronous motor is working in normal condition. What will happen to the speed of the rotor and the current of the power supply if the voltage of the power supply decreases suddenly?
Passage 6
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(2) Reduced-voltage starting 减压起动 ① Wye-Delta starting 星形－三角形减压起动 Appropriate for delta connection motor 适用于正常运行为Δ形联结的电动机。
Electric motor 单击此处编辑母版标题样式
18 If the frequency is 60 Hz, how about the speed of the magnetic field for different pairs of poles?
Passage 6
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Current complete one cycle
→RMF complete one cycle
Current complete 50 cycles per sec→ RMF complete 50 cycles Current change (50×60) cycles → RMF change3000 cycles per min
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Electric motor 单击此处编辑母版标题样式
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Electric motor 单击此处编辑母版标题样式
8 How to get the speed of RMF ?
Speed of rotating magnetic field n0 —— synchronous speed
1 n0 = 3000 = 60 f1 (r / min)
revolution per minute
Passage 6
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9 How to U change RMF? 1
V2 W2 U4 W1 V1 V3
V4
U1
U2
Each phase is composed of one coils
* Starting:
* Normal working:
n = 0, s = 1
sN = 0.01 ~ 0.09
Passage 6
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15 what is electromagnetic torque ? T = kT sR2U1p2 R22+(sX20) 2