A quick introduction to Sensorless Vector Control in PWM drive.

1. January 2013
Inverter Training
Hitachi Product Range
How an Inverter works and basic description of
V/F and Sensor-less Vector Control methods.

2. January 2013
DC bus
capacitor iM
PWM voltage
output
Motor
current
vM
vs
is
iM
Induction
Motor
Diode bridge
(Converter portion)AC
power
supply
IGBT
(Inverter portion)
0 0
vs is
0
Speed Control of a motor
using an Inverter.

3. January 2013
How to generate PWM output
Signal
Carrier
5V series
(MCU operation)
Output voltage of
the inverter
200Vrms / 400Vrms
Pulse Width
Modulation
15V series
(IGBT gate drive)
Speed Control of a motor
using an Inverter.

4. January 2013
How to generate PWM output
Big
signal
Carrier
Small
signal
Inverter output voltage
Speed Control of a motor
using an Inverter.

5. January 2013
V/f control method
f
V
k
f
E
k ≅⋅=Φ
Magnetizing flux
Stable magnetizing flux can be
achieved under constant E/f.
 Good for the motor!
Inverter gives out V/f =
constant
k ; constant
f ; frequency
Equivalent circuit of
one arm of motor
R1 L1
LM
R2
V E
f [Hz]
V [V]
V/f constant
Voltage/Frequency Control
Overview
Note: Max voltage is achieved when Output frequency = Base Frequency (Set on A003)

6. January 2013
Torque boost
Magnetizing flux weakens at low freq.
( )11 2 fLRiVE M π+⋅−=
1
1
2 L
f
Ri
f
V
f
E M
π−
⋅
−=∴
Constant Big when
f is low
f [Hz]
V [V]
Torque boost
 Compensation by torque boost function
R1 L1
LM
R2
V E
iM
Voltage/Frequency Control
Overview
Note: Torque boost is set on A028 and Torque boost point is set on A029.

7. January 2013
V/f characteristics
Base f & Max. f
depends on the motor.
f [Hz]
V [V]
Vmax
f [Hz]Base f Max. f
Constant
torque
output
Constant
power
output
Torque
Voltage/Frequency Control
Overview

8. January 2013
Sensor-Less Vector Control
Advantages of Vector control
 Achieve high torque automatically at low speed.
 Achieve quick and stable torque response.
Suitable application for SLV control
 Screw conveyer, Mixer, Crane, Lift, etc.
(Application requires high torque at low speed.)
Sensor-less Vector Control
Overview
E Drive - 150% Starting Torque or more.
CP2000 - 120% Overload 60 seconds to 150% Starting Torque.
C2000 - 150% Torque at 0Hz (with encoder).