The load should be connected between the U and V phases as shown. The drive attempts to produces a square wave of output current at the frequency defined by the Post Ramp Reference (02.001). The magnitude of the current is
controlled by the Torque Reference (04.008) as a percentage of the Rated Current (05.007). Iq, Torque Producing Current (04.002) shows the magnitude of the output current, which for a square wave is the same as the r.m.s. value of
current. The following should be noted about this control mode:
1. Id, Magnetising Current (04.017) remains at zero, and Current Magnitude (04.001) = Iq, Torque Producing Current (04.002).
2. Output Power (05.003) shows the correct magnitude of output power flowing from the drive, but this will always be positive whatever the phase relationship between the output current and voltage.
3. The maximum possible output voltage from the drive is a square wave with a magnitude approximately equal to the D.c. Bus Voltage (05.005).
4. High performance current controller mode is used and the current controller gains should be set up based on the load impedance for this mode as defined in the description of Current Controller Kp Gain (04.013) for RFC-A and
RFC-S modes.
5. The drive thermal model will provide protection for the drive as though the output frequency is 0Hz whatever the value of the Post Ramp Reference (02.001). This should be taken into account because the thermal capabilities of
the drive in this mode are the same as other modes when the motor is at standstill.
Parameter 05.015 Low Frequency Voltage Boost
Short description Defines the level of voltage boost at 0Hz when using a fixed V to F relationship
Mode Open‑Loop
Minimum 0.0 Maximum 25.0
Default 3.0 Units %
Type 8 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 1
Coding RW, BU
The default value for this parameter depends on the frame size of the drive as follows:
3.0% up to frame size 06 drives,
2.0% for frame size 07and frame size 08 drives
1.0% for larger sizes
See Open-loop Control Mode (05.014).
Parameter 05.017 Stator Resistance
Short description Defines the resistance of the motor stator
Mode Open‑Loop
Minimum 0.000000 Maximum 1000.000000
Default 0.000000 Units Ω
Type 32 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 6
Coding RW, RA
The Stator Resistance (05.017), Transient Inductance (05.024) and Stator Inductance (05.025) are derived from the star connected per phase equivalent circuit of an induction motor shown below.
The steady state parameters are converted to equivalent transient model parameters:
R
s
= R
1
L
m
= L
m
L
s
= L
1
+ L
m
L
r
= L
2
+ L
m
σL
s
= L
s
- (L
m
2
/ L
r
)
The equivalent drive parameters are:
Stator Resistance (05.017) = R
s
Transient Inductance (05.024) = σL
s
Stator Inductance (05.025) = L
s
To Next Page
Loading...
