Rockwell Automation Liqui-Flo AC GP Vector Drive Version 6.4 - Manual (Page 139)

Programming Reference 4-57
The level of increased output frequency is a function of the value entered in H.004 and
the motor current.
Actual motor shaft speed is determined by two factors: inverter output frequency and
the slip of the motor. The speed reference is converted into output frequency. Motor
slip is determined by the type of induction motor and varies with load.
At rated load, slip compensation measures inverter output current and increases the
output frequency by the percentage entered in H.004. Below rated load, slip
compensation will increase inverter output frequency by the percentage in H.004
multiplied by the percent of rated load.
Because of load changes, the long-term speed behavior of the motor is greatly
improved through the use of this parameter.
To calculate the value entered for H.004, use the following equation:
H.004 = 100 x Synchronous RPM - Nameplate RPM x Max Power Module Amps
Synchronous RPM Motor Nominal Current
Synchronous RPM = 120 x F
No. of Motor Poles
Example: 1722 RPM
Motor Nominal Current = 78% of Maximum Power Module Amps (P.095)
V/Hz regulation
2 kHz
H.004 = 100 x 1800 - 1722 x 100% = 5.56%
1800 78%
If the parameter is set to zero, motor speed will not be proportional to reference, but
will vary depending on load.
H.004 Slip Compensation
This parameter is
used to improve
motor speed
regulation by
increasing the output
frequency applied to
the motor (the
percentage of
frequency rise at
Power Module Output
Amps (P.095)). Parameter Range: 0.0% to 10.0% of base frequency (H.001)
Default Setting: 0.0% (no slip compensation)
Parameter Type: Tunable
Refer also to parameters: P.095 Power Module Output Amps
H.001 Motor Nameplate Base Frequency