Enable High Speed Servo Mode; Voltage Offset - Control Techniques unidrive sp Advanced User's Manual

Parameter Keypad and Parameter
structure display x.00
5.22

Enable high speed servo mode

Drive modes Servo
Bit SP
Coding
1
Default Servo
Update rate Background read
High speed servo mode is not enabled as default. Care must be taken when using this mode with servo motors to avoid damaging the drive. The
voltage produced by the servo motor magnets is proportional to speed. For high speed operation the drive must apply currents to the motor to
counter-act the flux produced by the magnets. It is possible to operate the motor at very high speeds that would give a very high motor terminal
voltage, but this voltage is prevented by the action of the drive. If however, the drive is disabled (or tripped) when the motor voltages would be higher
than the rating of the drive without the currents to counter-act the flux from the magnets, it is possible to damage the drive. If high speed mode is
enabled the motor speed must be limited to the levels given in the table below unless an additional hardware protection system is used to limit the
voltages applied to the drive output terminals to a safe level.
Maximum motor
Drive voltage
speed
rating
(rpm)
400 / (Ke x √2)
200
800 / (Ke x √2)
400
955 / (Ke x √2)
575
1145 / (Ke x √2)
690
Ke is the ratio between r.m.s. line to line voltage produced by the motor and the speed in V/rpm. Care must also be taken not to de-magnetise the
motor. The motor manufacturer should always be consulted before using this mode.
5.23

Voltage offset

Drive modes Open-loop
Bit SP FI
Coding
Range Open-loop
Default Open-loop
Second motor
Open-loop
parameter
Update rate Background read
Due to various effects in the drive inverter a voltage offset must be produced before any current flows. To obtain good performance at low frequencies
where the machine terminal voltage is small this offset must be taken into account. The value shown in Pr 5.23 is this offset given in line to line rms
volts. It is not possible for the user to measure this voltage easily, and so the automatic measurement procedure should be used (see Pr 5.14 on page
114).
Transient inductance (σL
5.24
Drive modes Open-loop, Closed-loop vector, Servo
Bit SP FI
Coding
Range Open-loop, Closed-loop vector, Servo
Default Open-loop, Closed-loop vector, Servo
Second motor
Open-loop, Closed-loop vector, Servo
parameter
Update rate Background read
Open-loop, Closed-loop vector
With reference to the diagram overleaf, the transient inductance is defined as
σL
= L + (L .L / (L + L
s 1 2 m 2 m
Unidrive SP Advanced User Guide
Issue Number: 7
Parameter Advanced parameter
description format descriptions
FI DE Txt VM DP ND
0
Maximum safe line to line voltage
at the motor terminals (V rms)
400 / √2
800 / √2
955 / √2
1145 / √2
DE Txt VM DP ND
1
0.0 to 25.0 V
0.0
Pr 21.13
)
s
DE Txt VM DP ND
3
0.000 to 500.000 mH
0.000
Pr 21.14
))
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protocol
RA NC NV PT US RW BU
1 1
RA NC NV PT US RW BU
1 1 1
RA NC NV PT US RW BU
1 1 1
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PS
PS
1
PS
1
Menu 5
117