Rated Load Rpm / Rated Speed; Rated Voltage; Open Loop - Control Techniques unidrive sp Advanced User's Manual

Parameter Keypad and Parameter
structure display x.00
5.08

Rated load rpm / Rated speed

Drive modes Open-loop, Closed-loop vector, Servo
Bit SP
Coding
Closed-loop vector DP=2
Open-loop,
Range
Closed-loop
Open-loop,
Default Closed-loop vector
Servo
Second motor
Open-loop, Closed-loop vector, Servo
parameter
Update rate Background read

Open loop

The rated load rpm is used with the motor rated frequency and No. of poles to calculate the rated slip of induction machines in Hz.
rated slip (Hz) = rated motor frequency - (no. of pole pairs x motor full load rpm / 60)
= Pr 5.06 - ((Pr 5.11 / 2) x Pr 5.08 / 60)
If Pr 5.08 is set to 0 or to synchronous speed slip compensation is disabled. If slip compensation is required this parameter should be set to the
nameplate value, which should give the correct rpm for a hot machine. Sometimes it will be necessary to adjust this when the drive is commissioned
because the nameplate value may be inaccurate. Slip compensation will operate correctly both below base speed and within the field weakening
region. Slip compensation is normally used to correct for the motor speed to prevent speed droop as load is applied. The rated load rpm can be set
higher than synchronous speed to deliberately introduce speed droop. This can be useful to aid load sharing with mechanically coupled motors.
Closed loop vector
Rated load rpm is used with motor rated frequency to determine the full load slip of the motor which is used by the vector control algorithm. Incorrect
setting of this parameter has the following effects:
• Reduced efficiency of motor operation
• Reduction of maximum torque available from the motor
• Reduced transient performance
• Inaccurate control of absolute torque in torque control modes
The nameplate value is normally the value for a hot machine, however, some adjustment may be required when the drive is commissioned if the
nameplate value is inaccurate. Either a fixed value can be entered in this parameter or the drive rated speed optimisation system may be used to
automatically adjust this parameter (see Pr 5.16 on page 115). It should be noted that the optimisation system does not operate when closed-loop
vector mode is used with no position feedback (see Pr 3.24 on page 58).
Servo
The Rated load rpm defines the rated speed of the motor and is only used in the motor thermal protection scheme (see Pr 5.12 on page 109.) and to
determine the speed used in the auto tuning inertia test (see Pr 5.12 on page 109).
5.09

Rated voltage

Drive modes Open-loop, Closed-loop vector, Servo
Bit SP
Coding
Range Open-loop, Closed-loop, Servo
Default Open-loop, Closed-loop vector, Servo
Second motor
Open-loop, Closed-loop vector, Servo
parameter
Update rate Level 4 read
Open loop
The rated voltage is used in conjunction with the motor rated frequency (Pr 5.06) to define the voltage to frequency characteristic applied to the motor.
The following operating methods selected by Pr 5.14 are used to define the drive frequency to voltage characteristic.
Open-loop vector mode: Ur_S, Ur or Ur_I
A linear characteristic is used from 0Hz to rated frequency, and then a constant voltage above rated frequency. When the drive operates between
rated frequency/50 and rated frequency/4, full vector based stator resistance (Rs) compensation is applied. However there is a delay of 0.5s when the
drive is enabled during which only partial vector based compensation is applied to allow the machine flux to build up. When the drive operates
between rated frequency/4 and rated frequency/2 the Rs compensation is gradually reduced to zero as the frequency increases. For the vector
modes to operate correctly the stator resistance (Pr 5.17), motor rated power factor (Pr 5.10) and voltage offset (Pr 5.23) are all required to be set up
Unidrive SP Advanced User Guide
Issue Number: 7
Parameter Advanced parameter
description format descriptions
FI DE Txt VM DP ND
0 to 180,000 rpm
0.00 to 40,000.00 rpm
EUR: 1,500, USA: 1,800
EUR: 1450.00, USA: 1,770.00
3,000.00
Pr 21.08
FI DE Txt VM DP ND
1
0 to AC_VOLTAGE_SET_MAX V
200V rating drive: 230V
400V rating drive: EUR: 400V, USA: 480V
600V rating drive: 575V
690V rating drive: 690V
Pr 21.09
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Serial comms
Macros
protocol
RA NC NV PT US RW BU
1 1
RA NC NV PT US RW BU
1 1 1
Electronic Feature look-
Performance
nameplate up table
PS
1
PS
1
Menu 5
107