The Open-loop Voltage Mode (05.014) defines the voltage output mode, as given below. It should be noted that the maximum output voltage of the drive is

limited to a level just below D.c. Link Voltage (05.005) / √2. Therefore, if the drive is being supplied via its own rectifier input stage the output voltage is limited

to a level just below that of the supply voltage. If the drive is operating in voltage mode the output voltage is limited to Motor Rated Voltage (05.009) or the

maximum possible output voltage whichever is the lowest (also refer to Over Modulation Enable (05.020)).

0: Ur S (Resistance compensation, stator resistance measured at each start)

Resistance compensation is a form of stator flux oriented sensorless motor control. A linear frequency to voltage characteristic is used where the drive output

voltage is increased from 0V to Motor Rated Voltage (05.009). as the |Output Frequency (05.001)| increases from 0Hz to Motor Rated Frequency (05.006).

When the |Output Frequency (05.001)| is above Motor Rated Frequency (05.006) the output voltage is limited to Motor Rated Voltage (05.009). Vector based

stator resistance compensation is applied below Motor Rated Frequency (05.006) / 4 and then this is tapered off from Motor Rated Frequency (05.006) / 4 to

Motor Rated Frequency (05.006) / 2. This method controls the flux level correctly in the motor in the steady state provided the correct value of

Stator Resistance (05.017) is used.

If slip compensation is not being used (see Motor Rated Frequency (05.006) ) then additional voltage compensation can be applied below

Motor Rated Frequency (05.006) / 10 to have an additional torque boost at very low frequencies, see Low Frequency Estimator Threshold,

Low Frequency Torque adjustment (05.084).

The Stator Resistance (05.017) is measured each time the drive is started. This test can only be done with a stationary motor where the flux has decayed to

zero. Therefore this mode should only be used if the motor is guaranteed to be stationary each time the drive is enabled. To ensure that the measurement is

not carried out before the flux has decayed, there is a period of one second after the inverter has been disabled during which the test is not carried out if the

drive is re-started. The Stator Resistance (05.017) is not automatically saved in non-volatile memory after each test.

1: Ur (Resistance compensation with no stator resistance measurement)

Resistance compensation is used as in Ur S mode, but the Stator Resistance (05.017) is not measured.

2: Fixed (Fixed boost with linear characteristic)

A fixed frequency to voltage characteristic is used as shown above where the voltage at 0Hz is defined by Low Frequency Voltage Boost (05.015). The

voltage characteristic moves linearly with output frequency passing through four points determined by [Boost End Voltage (05.074) and Boost End Frequency

(05.075)], [Second Point Voltage (05.076) and Second Point Frequency (05.077)], Third point voltage (05.078) and Second Point Frequency (05.077), and

[Motor Rated Voltage (05.009) and Motor Rated Frequency (05.006)].

By default Boost End Frequency (05.075) is set to half the Motor Rated Frequency (05.006), Second Point Frequency (05.077) is set 55%

and Third point frequency (05.079) is set to 75%. Similarly by default Boost End Voltage (05.074) is set at half the Motor Rated Voltage (05.009),

Second Point Voltage (05.076) 55% and Third point voltage (05.078) is set to 75%. This is to produce the same characteristic as SK by default.

3: Ur Auto (Resistance compensation, stator resistance measured on first start)

Resistance compensation is used as in Ur S mode, but the Stator Resistance (05.017) is only measured once when the drive is first enabled. After the test has

been completed successfully the mode is changed to Ur mode and Stator Resistance (05.017) is saved to non-volatile memory. If Parameter Cloning (11.042)

is set to 3 or 4 the Stator Resistance (05.017) is also written to a non-volatile media card fitted in the drive. If the test fails the mode is changed to Ur mode,

but Stator Resistance (05.017) is not updated.

4: Ur I (Resistance compensation, stator resistance measured at power-up)

Resistance compensation is used as in Ur S mode, but the Stator Resistance (05.017) is only measured when the drive is enabled for the first time after each

power-up.

Description

Stator resistance and voltage offset measured at each start

No measurements

Fixed boost mode.

Stator resistance and voltage offset measured at first drive

enable

Stator resistance and voltage offset measured at each power-up

Square law characteristic

Fixed boost with zero slip at zero reference

Unidrive M200 Parameter Reference Guide

Issue: 01.05.00.10