Parameter 05.018 Maximum Switching Frequency
Short description Defines the maximum switching frequency that can be used by the drive
Mode Open‑Loop
Minimum 0 Maximum VM_SWITCHING_FREQUENCY
Default 1 Units kHz
Type 8 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 0
Coding RW, TE, VM, RA
Value Text
0 2
1 3
2 4
3 6
4 8
5 12
6 16
Maximum Switching Frequency (05.018) should be set to the required PWM switching frequency. The drive inverter will operate at this frequency unless the inverter temperature becomes too hot. Under these conditions the drive will
reduce the switching frequency in an attempt to avoid tripping (see Auto-switching Frequency Change (05.035) ). The actual switching frequency is shown in Switching Frequency (05.037). The switching frequency has a direct effect on
the sample rate for the current controllers (see Current Controller Kp Gain (04.013)). All other control tasks are at a fixed rate.
Task
Speed controller (RFC-A, RFC-S) 250μs
D.c. link voltage controller 1ms
Flux controller (RFC-A, RFC-S) 1ms
Parameter 05.019 High Stability Space Vector Modulation
Short description Set to 1 to enable High Stability Space Vector Modulation
Mode Open‑Loop
Minimum 0 Maximum 1
Default 0 Units
Type 1 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 0
Coding RW
If High Stability Space Vector Modulation (05.019) = 0 standard space vector modulation is used to derive the inverter control signals. If High Stability Space Vector Modulation (05.019) = 1 a modified form of space vector modulation is
selected which can give the following advantages:
1. With some motors instability can occur when operating below Rated Frequency (05.006) / 2 especially with light loads and high switching frequency. The preferred method to solve this problem is to use RFC-A mode
without position feedback. However, if Open-loop mode is required, the instability can sometimes be reduced by selecting high stability space vector modulation.
2. As the output voltage approaches the maximum available from the drive pulse deletion occurs. This can cause unstable operation with a lightly or fully loaded motor. High stability space vector modulation will reduce this
effect.
The disadvantages of using high stability space vector modulation are:
1. Increased acoustic noise from the motor.
2. A reduction in the thermal capability of the drive at low output frequencies.
Parameter 05.020 Quasi-square Enable
Short description Set to 1 to change the output voltage to a quasi-square wave
Mode Open‑Loop
Minimum 0 Maximum 1
Default 0 Units
Type 1 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 0
Coding RW
If Quasi-square Enable (05.020) = 0 then the output of the drive is limited to a modulation index of unity, which limits the output voltage to a level just below D.c. Bus Voltage (05.005) / √2. Therefore, if the drive is being supplied via its
own rectifier input stage the output voltage is limited to a level just below that of the supply voltage or Rated Voltage (05.009) whichever is lower.
If Quasi-square Enable (05.020) = 1 then the limit imposed by Quasi-square Enable (05.020) is ignored and the modulation index is allowed to increase beyond unity. As the output voltage increases the output voltage changes through
trapezoidal waveforms to a quasi-square wave output. This mode is useful where the ratio between the switching frequency and the fundamental output frequency is less than 12, as it removes any sub-harmonic effects that occur.
However, it does produce significant multiple odd harmonics of the output frequency in the output currents which cause acoustic noise, torque ripple and motor heating.
Parameter 05.024 Transient Inductance
Short description Defines the inducatance of the transient components in the motor stator
Mode Open‑Loop
Minimum 0.000 Maximum 500.000
Default 0.000 Units mH
Type 32 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 3
Coding RW, RA
See Stator Resistance (05.017).
Parameter 05.025 Stator Inductance
Short description Defines the inductance of the motor stator
Mode Open‑Loop
Minimum 0.00 Maximum 5000.00
Default 0.00 Units mH
Type 32 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 2
Coding RW, RA
See Stator Resistance (05.017).
Parameter 05.027 Enable Slip Compensation
Short description Set to 1 to enable slip compensation
Mode Open‑Loop
Minimum 0 Maximum 1
Default 1 Units
Type 1 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 0
Coding RW, BU
See Rated Frequency (05.006).
Parameter 05.031 Voltage Controller Gain
Short description Defines the proportional gain of the d.c. link voltage controller
Mode Open‑Loop
Minimum 1 Maximum 30
Default 1 Units
Type 8 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 0
Coding RW
Voltage Controller Gain (05.031) can be used to modify the proportional gain of the d.c. link voltage controller used for standard ramp and supply loss control.
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