# Menu 3 − Frequency and Speed Feedback

Mode: RFC‑A

The drive can operate under Open Loop and RFC modes with respect to frequency and current control and can drive asynchronous machines. The open loop asynchronous control is further broken down into vector and fixed boost modes

Parameter | 03.001 Final Demand Reference
--- | ---
Short description | Displays the final reference to the frequency controller
Mode | RFC‑A
Minimum | −VM_FREQ | Maximum | VM_FREQ
Default |  | Units | Hz
Type | 32 Bit Volatile | Update Rate | 16ms
Display Format | Standard | Decimal Places | 2
Coding | RO, FI, VM, ND, NC, PT

Open loop mode:
Final Demand Reference (03.001) shows the fundamental drive output frequency from the Post Ramp Reference (02.001) and the Hard Frequency Reference (03.022).

RFC modes:
Final Demand Reference (03.001) shows the reference at the input to the frequency controller, which is the sum of the Post Ramp Reference (02.001) if the ramp output is not disabled and the hard frequency reference (if enabled). If the drive is disabled Final Demand Reference (03.001) shows 0.00.

Parameter | 03.002 Estimated Frequency
--- | ---
Short description | Displays the frequency feedback selected for the frequency controller
Mode | RFC‑A
Minimum | −VM_FREQ | Maximum | VM_FREQ
Default |  | Units | Hz
Type | 32 Bit Volatile | Update Rate | 16ms
Display Format | Standard | Decimal Places | 2
Coding | RO, FI, VM, ND, NC, PT

Estimated Frequency (03.002) shows the level of the frequency feedback selected for the frequency controller.

Parameter | 03.003 Frequency Error
--- | ---
Short description | Displays the error between the final frequency demand and the estimated frequency
Mode | RFC‑A
Minimum | −VM_FREQ | Maximum | VM_FREQ
Default |  | Units | Hz
Type | 32 Bit Volatile | Update Rate | 16ms
Display Format | Standard | Decimal Places | 2
Coding | RO, FI, VM, ND, NC, PT

RFC modes only. Will be set to zero in open loop modes.

The frequency error is the difference between the final frequency demand and the estimated frequency and does not include the effect of the differential term in the frequency controller feedback branch.

Parameter | 03.004 Frequency Controller Output
--- | ---
Short description | Displays the output of the frequency controller
Mode | RFC‑A
Minimum | −VM_TORQUE_CURRENT | Maximum | VM_TORQUE_CURRENT
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | 16ms
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

RFC modes only. Will be set to zero in open loop modes.

The output of the frequency regulator is a torque demand given as a percentage of rated motor torque. It should be noted that this will be modified to take into account the level of motor flux if field weakening is active before it is converted into the Final Current Reference (04.004).

Parameter | 03.005 Zero Frequency Threshold
--- | ---
Short description | Defines the threshold for detecting the zero frequency condition
Mode | RFC‑A
Minimum | 0.00 | Maximum | 20.00
Default | 2.00 | Units | Hz
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW, BU

If the Post Ramp Reference (02.001) is at or below the level defined by this parameter in either direction Zero Frequency (10.003) = 1, otherwise Zero Frequency (10.003) = 0.

Parameter | 03.006 At Frequency Lower Limit
--- | ---
Short description | Defines the lower limit for detecting the at frequency condition
Mode | RFC‑A
Minimum | 0.00 | Maximum | 550.00
Default | 1.00 | Units | Hz
Type | 32 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW

At Frequency (10.006) is set if the Estimated Frequency (03.002) is on the boundaries or within the at speed window. Above Set Frequency (10.007) and Below Set Frequency (10.005) are set if the feedback is above or below the window respectively.

If Absolute At Frequency Select (03.009) = 0 reference window mode is used.
The "at speed" condition is true if,

> (|Pre-ramp Reference (01.003)| - At Frequency Lower Limit (03.006)) ≤ |Estimated Frequency (03.002)| ≤ (|Pre-ramp Reference (01.003)| + At Frequency Upper Limit (03.007))

(If the lower limit is less than zero then zero is used as the lower limit.)

If Absolute At Frequency Select (03.009) = 1 absolute window mode is used.
The "at speed" condition is true if,

> At Frequency Lower Limit (03.006) ≤ |Estimated Frequency (03.002)| ≤ At Frequency Upper Limit (03.007)

Note: All flags are cleared if Reference On (01.011) is 0.

Parameter | 03.007 At Frequency Upper Limit
--- | ---
Short description | Defines the upper limit for detecting the at frequency condition
Mode | RFC‑A
Minimum | 0.00 | Maximum | 550.00
Default | 1.00 | Units | Hz
Type | 32 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW

See At Frequency Lower Limit (03.006).

Parameter | 03.008 Over Frequency Threshold
--- | ---
Short description | Defines the threshold used to detect the over frequency condition
Mode | RFC‑A
Minimum | 0.00 | Maximum | 550.00
Default | 0.00 | Units | Hz
Type | 32 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW

If Over Frequency Threshold (03.008) is set to a non-zero value it defines the over frequency threshold. If the Estimated Frequency (03.002) exceeds this threshold in either direction an Over Speed trip is produced. If Over Frequency Threshold (03.008) is set to 0.0 the threshold is based on the variable minimum/maximum for the references and is equal to 1.2 x VM_SPEED_FREQ_REF[MAX].

Parameter | 03.009 Absolute At Frequency Select
--- | ---
Short description | Set to 1 to select absolute at frequency
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

See At Frequency Lower Limit (03.006).

Parameter | 03.010 Frequency Controller Proportional Gain Kp1
--- | ---
Short description | Defines the proportional gain for frequency controller 1
Mode | RFC‑A
Minimum | 0.000 | Maximum | 200.000
Default | 0.100 | Units | s/rad
Type | 32 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 3
Coding | RW

RFC modes only.

The diagram below shows a generalised representation of the frequency controller. The controller includes a feed forward proportional gain (Kp), a feed forward integral gain (Ki), and a differential feedback gain (Kd).

The drive holds two sets of these gains and either set may be selected for use by the frequency controller with Frequency Controller Gain Select (03.016). If Frequency Controller Gain Select (03.016) = 0, gains Kp1, Ki1 and Kd1 are used, and if Frequency Controller Gain Select (03.016) = 1, gains Kp2, Ki2 and Kd2 are used.

If Frequency Controller Gain Select (03.016) = 2, Kp1 etc are used while the modulus of the frequency demand is less than the value held by Gain Change Threshold (03.017), else Kp2 etc will be used.

If Frequency Controller Gain Select (03.016) is changed when the drive is enabled, the controller output is kept constant by modifying the level of the integral term accumulator so that the transient produced is minimised.

Proportional gain (Kp)
If Kp is non-zero and Ki is zero the controller will only have a proportional term, and there must be a frequency error to produce a torque reference. Therefore as the motor load increases there will be a difference between the reference and actual frequencies. This effect, called regulation, depends on the level of the proportional gain, the higher the gain the smaller the frequency error for a given load. If the proportional gain is too high the closed-loop stability limit may be reached.

Integral gain (Ki)
The integral gain is provided to prevent frequency regulation. The error is accumulated over a period of time and used to produce the necessary torque reference without any frequency error. Increasing the integral gain reduces the time taken for the frequency to reach the correct level and increases the stiffness of the system, i.e. it reduces the positional displacement produced by applying a load torque to the motor. Unfortunately increasing the integral gain also reduces the system damping giving overshoot after a transient. For a given integral gain the damping can be improved by increasing the proportional gain. A compromise must be reached where the system response, stiffness and damping are all adequate for the application. The integral term is implemented in the form of ?(Ki x error), and so the integral gain can be changed when the controller is active without causing large transients on the torque reference.

Differential gain (Kd)
The differential gain is provided in the feedback of the frequency controller to give additional damping. The differential term is implemented in a way that does not introduce excessive noise normally associated with this type of function. Increasing the differential term reduces the overshoot produced by under-damping, however for most applications the proportional and integral gains alone are sufficient.

It should be noted that the differential term is limited internally so that it is ineffective if frequency in Hz x Kd x Ki is greater than 170.

To analyse the performance of the frequency controller it may be represented as an s-domain model as shown below.

Kc' is the conversion between the frequency controller output and the torque producing current reference. A value of unity at the output of the frequency controller gives a torque producing current equal to Kc'. The drive automatically compensates the torque producing current reference for flux variations in field weakening, and so Kc' can be assumed to have a constant value even in field weakening. Kc' = Full Scale Current Kc (11.061) x 0.45.

Kt is the torque constant of the motor (i.e. torque in Nm per amp of torque producing current). For induction motors the value must be calculated from the motor parameters. In RFC-A mode this calculation is performed by the drive and the result is stored in Torque Per Amp (05.032).

L(s) is the transfer function of the load.

Parameter | 03.011 Frequency Controller Integral Gain Ki1
--- | ---
Short description | Defines the integral gain for frequency controller 1
Mode | RFC‑A
Minimum | 0.00 | Maximum | 655.35
Default | 0.10 | Units | s²/rad
Type | 16 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 2
Coding | RW, BU

RFC modes only.

See Frequency Controller Proportional Gain Kp1 (03.010).

Parameter | 03.012 Frequency Controller Differential Feedback Gain Kd1
--- | ---
Short description | Defines the differential gain for frequency controller 1
Mode | RFC‑A
Minimum | 0.00000 | Maximum | 0.65535
Default | 0.00000 | Units | 1/rad
Type | 16 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 5
Coding | RW, BU

RFC modes only.

See Frequency Controller Proportional Gain Kp1 (03.010).

Parameter | 03.013 Frequency Controller Proportional Gain Kp2
--- | ---
Short description | Defines the proportional gain for frequency controller 2
Mode | RFC‑A
Minimum | 0.000 | Maximum | 200.000
Default | 0.100 | Units | s/rad
Type | 32 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 3
Coding | RW

RFC modes only.

See Frequency Controller Proportional Gain Kp1 (03.010).

Parameter | 03.014 Frequency Controller Integral Gain Ki2
--- | ---
Short description | Defines the integral gain for frequency controller 2
Mode | RFC‑A
Minimum | 0.00 | Maximum | 655.35
Default | 0.10 | Units | s²/rad
Type | 16 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 2
Coding | RW, BU

RFC modes only.

See Frequency Controller Proportional Gain Kp1 (03.010).

Parameter | 03.015 Frequency Controller Differential Feedback Gain Kd2
--- | ---
Short description | Defines the differential gain for frequency controller 2
Mode | RFC‑A
Minimum | 0.00000 | Maximum | 0.65535
Default | 0.00000 | Units | 1/rad
Type | 16 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 5
Coding | RW, BU

RFC modes only.

See Frequency Controller Proportional Gain Kp1 (03.010).

Parameter | 03.016 Frequency Controller Gain Select
--- | ---
Short description | Defines which gains are used for the frequency controller
Mode | RFC‑A
Minimum | 0 | Maximum | 2
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | 16ms
Display Format | Standard | Decimal Places | 0
Coding | RW

RFC modes only.

See Frequency Controller Proportional Gain Kp1 (03.010).

Value | Selection
0 | Kp1, Ki1 & Kd1 used
1 | Kp2, Ki2 & Kd2 used
2 | Automatic gain change at frequency threshold (Gain Change Threshold (03.017))

Parameter | 03.017 Gain Change Threshold
--- | ---
Short description | Defines the threshold that changes between the two sets of gains for the frequency controller
Mode | RFC‑A
Minimum | 0.00 | Maximum | 550.00
Default | 0.00 | Units | Hz
Type | 32 Bit User Save | Update Rate | 16ms
Display Format | Standard | Decimal Places | 2
Coding | RW

RFC modes only.

See Frequency Controller Proportional Gain Kp1 (03.010).

Parameter | 03.018 Motor and Load Inertia
--- | ---
Short description | Displays the inertia of the motor and load
Mode | RFC‑A
Minimum | 0.00 | Maximum | 1000.00
Default | 0.00 | Units | kgm²
Type | 32 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW

The motor and load inertia represents the total inertia driven by the motor. This is used to provide torque feed-forwards during acceleration when required (see Torque Mode Selector (04.011)).

It is possible to measure the inertia as part of the auto-tune process (See Auto-tune (05.012))

Parameter | 03.022 Hard Frequency Reference
--- | ---
Short description | Defines the value of the hard frequency reference
Mode | RFC‑A
Minimum | −VM_SPEED_FREQ_REF | Maximum | VM_SPEED_FREQ_REF
Default | 0.00 | Units | Hz
Type | 32 Bit User Save | Update Rate | 4ms
Display Format | Standard | Decimal Places | 2
Coding | RW, VM

The Hard Frequency Reference (03.022) is a reference value which does not pass through the ramp system, but is added directly to the Post Ramp Reference (02.001). The Hard Frequency Reference (03.022) is only added when selected by the Hard Frequency Reference Select (03.023) and Reference On (01.011) is active.

Parameter | 03.023 Hard Frequency Reference Select
--- | ---
Short description | Set to 1 to enable the use of the hard frequency reference
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | 4ms
Display Format | Standard | Decimal Places | 0
Coding | RW

See Hard Frequency Reference (03.022).

Parameter | 03.029 Position
--- | ---
Short description | Displays the position counter in frequency or encoder mode
Mode | RFC‑A
Minimum | 0 | Maximum | 65535
Default |  | Units |
Type | 16 Bit Power Down Save | Update Rate | Background
Display Format | Standard | Decimal Places | 0
Coding | RO, FI, ND, NC, PT, BU

Indicates the current value of the position counter in Frequency or Encoder mode. Position is reset to 0 if Position Counter Reset (03.032) is 1.

Parameter | 03.032 Position Counter Reset
--- | ---
Short description | Set to 1 to reset the position counter
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit Volatile | Update Rate | Background
Display Format | Standard | Decimal Places | 0
Coding | RW, NC

When set, this parameter resets the position parameter (Position (03.029)).

Parameter | 03.035 Position Scaling Numerator
--- | ---
Short description | Defines the numerator used for scaling the pulse counter
Mode | RFC‑A
Minimum | 0.000 | Maximum | 1.000
Default | 1.000 | Units |
Type | 16 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 3
Coding | RW, BU

Position Scaling Numerator (03.035) and Position Scaling Denominator (03.036) are used to scale the pulse counter down to the required position units. The multiplying factor applied to the counter is defined as:

Position Scaling Numerator (03.035) ÷ Position Scaling Denominator (03.036)

Parameter | 03.036 Position Scaling Denominator
--- | ---
Short description | Defines the denonminator used for scaling the pulse counter
Mode | RFC‑A
Minimum | 0.000 | Maximum | 100.000
Default | 1.000 | Units |
Type | 32 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 3
Coding | RW

See Position Scaling Numerator (03.035).

Parameter | 03.037 Frequency Output or PWM Output Scaling
--- | ---
Short description | Defines the scaling factor applied to the frequency or PWM output
Mode | RFC‑A
Minimum | 0.000 | Maximum | 4.000
Default | 1.000 | Units |
Type | 16 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 3
Coding | RW, BU

Scale factor applied to the frequency or PWM output.

Parameter | 03.038 Maximum Output Frequency
--- | ---
Short description | Defines the maximum frequency required at the frequency output
Mode | RFC‑A
Minimum | 0 | Maximum | 3
Default | 2 | Units | kHz
Type | 8 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 0
Coding | RW, TE, BU

Value | Text | Description
0 | 1 | 15.1 bit resolution at Fmax
1 | 2 | 14.1 bit resolution at Fmax
2 | 5 | 12.8 bit resolution at Fmax
3 | 10 | 11.8 bit resolution at Fmax

Defines the maximum frequency required at the frequency output. The choice of maximum output frequency depends on the requirement of the output. Due to limitations in the hardware, higher output frequencies do not offer the best resolution at the top end of the frequency range.1, 2, 5, and 10kHz (0 - 3).

Fmax (kHz) | Resolution at Fmax
1 | 10 bit
2 | 9
5 | 8
10 | 7.7

Parameter | 03.042 Frequency Input High Precision
--- | ---
Short description | Increase the frequency input measuring window
Mode | RFC‑A
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 0
Coding | RW

If Frequency Input High Precision (03.042) = 1 then the frequency input measurement window is doubled. This doubles the accuracy of the frequency input measurment but increase the response time by two.

If Frequency Input High Precision (03.042) = 0 then the frequency input measurement window is similar to Commander SK with better response time.

Parameter | 03.043 Maximum Reference Frequency
--- | ---
Short description | Defines the maximum frequency expected at the frequency input
Mode | RFC‑A
Minimum | 0.00 | Maximum | 100.00
Default | 10.00 | Units | kHz
Type | 16 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 2
Coding | RW

Defines the maximum frequency expected at the frequency input. The time the frequency is measured over is defined by

Measurement Time = 2048 / Maximum reference frequency

With a maximum measurement time of 0.341 seconds.
2048 is used to give the measurement more stability. The output is 10 bits.
Maximum reference frequency of less than 6kHz will have a lower resolution.

Parameter | 03.044 Frequency Reference Scaling
--- | ---
Short description | Defines the scaling factor applied to the frequency reference
Mode | RFC‑A
Minimum | 0.000 | Maximum | 4.000
Default | 1.000 | Units |
Type | 16 Bit User Save | Update Rate | Background
Display Format | Standard | Decimal Places | 3
Coding | RW, BU

Scale factor applied to the frequency reference.

Parameter | 03.045 Frequency Reference
--- | ---
Short description | Displays the frequency reference
Mode | RFC‑A
Minimum | 0.00 | Maximum | 100.00
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | 16ms
Display Format | Standard | Decimal Places | 2
Coding | RO, FI, ND, NC, PT

Indicates the reference input if Digital input 5 mode (08.035) = 4.

The reference has a 16ms filter.

Parameter | 03.047 Two Point Minimum Frequency
--- | ---
Short description | Defines the minimum frequency for scaling the frequency input
Mode | RFC‑A
Minimum | 0.00 | Maximum | 100.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW

Frequency Reference (03.045) is scaled and limited using:

- Two Point Minimum Frequency (03.047)
- Drive Reference at Minimum Frequency (03.048)
- Two Point Maximum Frequency (03.049)
- Drive Reference at Maximum Frequency (03.050)

Parameters above can be selected to limit the range of Frequency Reference (03.045) and also scale it between the minimum and maximum reference.

Parameter | 03.048 Drive Reference at Minimum Frequency
--- | ---
Short description | Defines the drive reference for scaling the frequency input at minimum frequency
Mode | RFC‑A
Minimum | 0.00 | Maximum | 100.00
Default | 0.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW

See Two Point Minimum Frequency (03.047).

Parameter | 03.049 Two Point Maximum Frequency
--- | ---
Short description | Defines the maximum frequency for scaling the frequency input
Mode | RFC‑A
Minimum | 0.00 | Maximum | 100.00
Default | 100.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW

See Two Point Minimum Frequency (03.047).

Parameter | 03.050 Drive Reference at Maximum Frequency
--- | ---
Short description | Defines the drive reference for scaling the frequency input at maximum frequency
Mode | RFC‑A
Minimum | 0.00 | Maximum | 100.00
Default | 100.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW

See Two Point Minimum Frequency (03.047).

Parameter | 03.072 Motor speed percent
--- | ---
Short description | Displays the final demand reference as a percentage of the reference clamp
Mode | RFC‑A
Minimum | -150.0 | Maximum | 150.0
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | Background write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, ND, NC, PT

Motor speed percent (03.072) displays the Final Demand Reference (03.001) as a percentage of the reference clamp.

If Final Demand Reference (03.001) >= 0.00Hz then

> If Maximum Reference Clamp (01.006) = 0.00Hz then

> > Motor speed percent (03.072) = 0.0%

> else

> Motor speed percent (03.072) = Final Demand Reference (03.001) x 100 / Maximum Reference Clamp (01.006)

else

> If Negative Reference Clamp Enable (01.008) = 1 then

> > If Maximum Reference Clamp (01.006) = 0.00Hz then

> > > Motor speed percent (03.072) = 0.0%

> > else

> > > Motor speed percent (03.072) = -Final Demand Reference (03.001) x 100 / Minimum Reference Clamp (01.007)

> else

> > If Maximum Reference Clamp (01.006) = 0.00Hz then

> > > Motor speed percent (03.072)= 0.0%

> > else

> > Motor speed percent (03.072) = -Final Demand Reference (03.001) x 100 / (-Maximum Reference Clamp (01.006))

Parameter | 03.079 Sensorless Mode Filter
--- | ---
Short description | Defines the time constant for the filter applied to the output of the frequency estimator system
Mode | RFC‑A
Minimum | 0 | Maximum | 5
Default | 0 | Units | ms
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | 4
1 | 5
2 | 6
3 | 8
4 | 12
5 | 20

A filter with a 4ms time constant is always applied to the output of the frequency estimator system used for sensorless operation in closed loop mode. This time constant may be extended by increasing Sensorless Mode Filter (03.079) above 0. The output of the frequency estimator can include some ripple, which increases as the drive passes into field weakening and the filter can be used to remove this ripple. This is particularly useful when using standard ramp or spinning start with a low friction high inertia load, and can prevent over voltage trips when the drive has no braking resistor.

Parameter | 03.080 Sensorless Position
--- | ---
Short description | Displays the motor position representing a movement equivalent to one pole of the motor
Mode | RFC‑A
Minimum | 0 | Maximum | 65535
Default |  | Units |
Type | 16 Bit Volatile | Update Rate | 16ms
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC, PT, BU

Sensorless Position (03.080) gives the motor position representing a movement equivalent to one pole of the motor.

For example in a rotary application with a 4 pole motor, the movement associated with one pole is a mechanical movement of 180°. Sensorless Position (03.080) is aligned as for a position feedback device with 0° phasing angle.