Menu 2 − Speed Ramps

Mode: RFC‑A

The Post Ramp Reference (02.001) indicates the final frequency or speed reference at the input to Frequency Monitoring (03) .

It should be noted that the ramps are applied during starting and stopping (i.e. when Reference On (01.011) changes from 0 to 1 and vice versa). This is achieved on starting by making the ramp output equal to Speed Feedback (03.002). (See Catch A Spinning Motor (06.009) for more details). On stopping, the ramp output is made equal to Final Speed Reference (03.001) and the setting of Disable Ramp Output (02.005) is ignored and so the ramp is always used, but just while the drive is in the deceleration state. If ramps are not required on stopping then stopping without ramps should be used (i.e. Stop Mode (06.001) should be set for no ramp stop). The same feature is applied when stopping when the supply is lost, so that if Supply Loss Mode (06.003) is set to select a ramped stop, the speed will be ramped to standstill even if the hard speed reference is being used. 

If Ramp Hold (02.003) = 0 the ramp system functions normally. If Ramp Hold (02.003) is set to 1 and S Ramp Enable (02.006) = 0 the ramp system output is held at its current level. If Ramp Hold (02.003) is subsequently set to 0 the ramp system output is released and continues to operate normally. If a drive stop is requested (i.e. Reference On (01.011) = 0) the ramp hold function is disabled.

Acceleration is defined as a positive (forward) or negative (reverse) frequency or speed change away from zero, and deceleration is defined as a change towards zero. Ramp Mode (02.004) defines the ramp mode used for deceleration. During acceleration the frequency or speed changes are based on the final acceleration rate only.

0: Fast ramp
During deceleration the frequency or speed changes are based on the final deceleration rate.

1: Standard ramp 
If the d.c. bus voltage rises to the level defined by Standard Ramp Voltage (02.008) the regenerative current limit is modified to prevent the voltage from rising any higher. This form of control applies to speed or torque control and during supply loss. If the Standard Ramp Voltage (02.008) is set to a level that is below the nominal d.c. bus voltage level the motor is likely to accelerate with a low level of torque. The waveforms below show the behaviour of the system when the speed reference is set to zero and standard ramp control becomes active. In the first example the speed reference (ramp output) reaches zero before the actual speed reaches zero because the deceleration is being controlled to limit the d.c. link voltage. Then when standard ramp control becomes inactive the ramp output is set to the actual speed, so that the required ramp rate is used to decelerate to stop. In the second example the reference is reapplied before the speed reaches zero. Because the speed reference has fallen faster than the actual speed, there is a recovery time before the speed reference rises to meet the actual speed.

See Ramp Mode (02.004).

In the following circumstances it is possible that the motor may not decelerated or even accelerate.

1. When standard ramp is selected with a high inductance supply it is possible for the d.c. bus voltage to rise as the motor speed approaches zero, and so the motor will continue to rotate slowly and not stop.
2. An overhauling load can cause the motor to accelerate.

It can be a problem if the drive state is changed to the "Decelerating" state and the motor does not stop. If Deceleration Fail Detection Disable (02.009) is at its default value of 0, the motor frequency or speed is monitored in the "Decelerating" state, and if this does not fall over a period of 10s the ramp output is forced to zero and the drive state is changed to "Stop" or "Inhibit" as appropriate.

If Deceleration Fail Detection Disable (02.009) = 1 this feature is disabled. This can be used in the following circumstances to prevent the system state from changing from the "Decelerating" state before the motor has stopped:

1. If S ramps are being used with long ramp rates, and the motor is still accelerating when the drive is changed to the "Decelerating" state because the run command is removed, then the ramp output may increase further before falling again towards zero.
2. In RFC-A or RFC-S modes the speed may appear not to reduce when very long ramp rates are used.

The Acceleration Rate Selector (02.010) is used to select an acceleration rate by the Pump software. The the following table shows the rates that may be selected:

This defines the acceleration rate in Hand and Auto, except when a pump cleaning or de-ragging cycle is running.

The units of General Acceleration Rate (02.011), Cleaning Phase 1 Acceleration Rate (02.012), Cleaning Phase 2 Acceleration Rate (02.013),  Cleaning Phase 3 Acceleration Rate (02.014) and Intermediate Cascade Acceleration Rate (02.015) are s / Ramp rate frequency or s / Ramp rate speed. See Ramp Rate Units (02.039) for the definition of Ramp rate frequency and Ramp rate speed.

Selecting a ramp rate that has been set to zero in Open-loop mode disables the ramp system so that the Post Ramp Reference (02.001) follows thePre-ramp Reference (01.003) without any delay for acceleration or deceleration. It should be noted that this also disables the standard ramp d.c. link voltage controller and the frequency based current limits.

This defines the acceleration rate when executing phase 1 of the cleaning or de-ragging routine; See Cleaning Phase 1 Time At Reference (29.093).

See also General Acceleration Rate (02.011).

This defines the acceleration rate when executing phase 2 of the cleaning or de-ragging routine; See Cleaning Phase 1 Time At Reference (29.093).

See also General Acceleration Rate (02.011).

This defines the acceleration rate when executing phase 3 of the cleaning or de-ragging routine; See Cleaning Phase 1 Time At Reference (29.093).

See also General Acceleration Rate (02.011).

This defines the acceleration rate used to change the speed of the leader pump when removing a cascade assist pump from the system. Increasing the speed of the leader pump in this situation helps to prevent under-pressure when the assist pump is removed.  

See also General Acceleration Rate (02.011).

The Deceleration Rate Selector (02.020) is used to select an acceleration rate by the Pump software. The the following table show the selections possible:

This defines the acceleration rate in Hand and Auto, except when a pump cleaning or de-ragging cycle is running.

The units of General Deceleration Rate (02.021), Cleaning Phase 1 Deceleration Rate (02.022), Cleaning Phase 2 Deceleration Rate (02.023) and Cleaning Phase 3 Deceleration Rate (02.024) are s / Ramp rate frequency or s / Ramp rate speed. See Ramp Rate Units (02.039) for the definition of Ramp rate frequency and Ramp rate speed.

Selecting a ramp rate that has been set to zero in Open-loop mode disables the ramp system so that the Post Ramp Reference (02.001) follows thePre-ramp Reference (01.003) without any delay for acceleration or deceleration. It should be noted that this also disables the standard ramp d.c. link voltage controller and the frequency based current limits.

This defines the deceleration rate when executing phase 1 of the cleaning or de-ragging routine; See Cleaning Phase 1 Time At Reference (29.093).

See also General Deceleration Rate (02.021).

This defines the deceleration rate when executing phase 2 of the cleaning or de-ragging routine; See Cleaning Phase 1 Time At Reference (29.093).

See also General Deceleration Rate (02.021).

This defines the deceleration rate when executing phase 3 of the cleaning or de-ragging routine; See Cleaning Phase 1 Time At Reference (29.093).

See also General Deceleration Rate (02.021).

This defines the deceleration rate used to change the speed of the leader pump when adding a cascade assist pump to the system. Reducing the speed of the leader pump in this situation helps to prevent over-pressure when the assist pump is added.  

See also General Deceleration Rate (02.021).

Acceleration Rate Selected (02.030) shows the acceleration rate that has been selected by the Pump software. The following table shows the rates that may be selected:

Deceleration Rate Selected (02.031) the deceleration rate that has been selected by the Pump software. The the following table show the selections possible:

The ramp rate parameters (General Acceleration Rate (02.011), Cleaning Phase 1 Acceleration Rate (02.012), Cleaning Phase 2 Acceleration Rate (02.013), Cleaning Phase 3 Acceleration Rate (02.014), General Deceleration Rate (02.021), Cleaning Phase 1 Deceleration Rate (02.022), Cleaning Phase 2 Deceleration Rate (02.023) and Cleaning Phase 3 Deceleration Rate (02.024)) are specified in s / Ramp rate frequency for Open-loop mode and s / Ramp rate speed for RFC-A and RFC-S modes. Ramp rate frequency and Ramp rate speed are selected with Ramp Rate Units (02.039) as defined in the table below.