The load should be connected between the U and V phases as shown. The drive attempts to produces a square wave of output current at the frequency defined by the Post Ramp Reference (02.001). The magnitude of the current is

controlled by the Torque Reference (04.008) as a percentage of the Rated Current (05.007). Iq, Torque Producing Current (04.002) shows the magnitude of the output current, which for a square wave is the same as the r.m.s. value of

current. The following should be noted about this control mode:

1. Id, Magnetising Current (04.017) remains at zero, and Current Magnitude (04.001) = Iq, Torque Producing Current (04.002).

2. Output Power (05.003) shows the correct magnitude of output power flowing from the drive, but this will always be positive whatever the phase relationship between the output current and voltage.

3. The maximum possible output voltage from the drive is a square wave with a magnitude approximately equal to the D.c. Bus Voltage (05.005).

4. High performance current controller mode is used and the current controller gains should be set up based on the load impedance for this mode as defined in the description of Current Controller Kp Gain (04.013) for RFC-A and

RFC-S modes.

5. The drive thermal model will provide protection for the drive as though the output frequency is 0Hz whatever the value of the Post Ramp Reference (02.001). This should be taken into account because the thermal capabilities of

the drive in this mode are the same as other modes when the motor is at standstill.

Parameter

05.015 Low Frequency Voltage Boost

Short description

Defines the level of voltage boost at 0Hz when using a fixed V to F relationship

Mode

Open‑Loop

Minimum

0.0

Default

3.0

Type

8 Bit User Save

Display Format

Standard

Coding

RW, BU

The default value for this parameter depends on the frame size of the drive as follows:

3.0% up to frame size 06 drives,

2.0% for frame size 07and frame size 08 drives

1.0% for larger sizes

See Open-loop Control Mode (05.014).

Parameter

05.017 Stator Resistance

Short description

Defines the resistance of the motor stator

Mode

Open‑Loop

Minimum

0.000000

Default

0.000000

Type

32 Bit User Save

Display Format

Standard

Coding

RW, RA

The Stator Resistance (05.017), Transient Inductance (05.024) and Stator Inductance (05.025) are derived from the star connected per phase equivalent circuit of an induction motor shown below.

The steady state parameters are converted to equivalent transient model parameters:

= R

= L

+ L

= L

+ L

σL

= L

- (L

/ L

)

The equivalent drive parameters are: