Nidec Unidrive M200 - Page 50

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50 Unidrive M200 / M201 Control User Guide
Issue Number: 2
Pr 41 {05.014} Control Mode (cont)
For mode 2 and 5, at low frequencies (from 0 Hz to ½ x Pr 39) a voltage boost is applied as defined by Pr 42 as shown below:
Pr 05.027 Enable Slip Compensation
When a motor, being controlled in open loop mode, has load applied a characteristic of the motor is that the output speed droops in proportion to the
load applied as shown:
In order to prevent the speed droop shown above slip compensation should be enabled. To enable slip compensation Pr 05.027 must be set to a
100 % (this is the default setting), and the motor rated speed must be entered in Pr 07 (Pr 05.008).
The motor rated speed parameter should be set to the synchronous speed of the motor minus the slip speed. This is normally displayed on the
motor nameplate, i.e. for a typical 18.5 kW, 50 Hz, 4 pole motor, the motor rated speed would be approximately 1465 rpm. The synchronous speed
for a 50 Hz, 4 pole motor is 1500 rpm, so therefore the slip speed would be 35 rpm. If the synchronous speed is entered in Pr 07, slip compensation
will be disabled. If too small a value is entered in Pr 07, the motor will run faster than the demanded frequency. The synchronous speeds for 50 Hz
motors with different numbers of poles are as follows:
2 pole = 3000 rpm, 4 pole = 1500 rpm, 6pole =1000 rpm, 8 pole = 750 rpm
Output
voltage
Pr / 208
Pr 08
Pr / 239
Pr 39
Output
frequency
Output voltage characteristic
(Fd)
Voltage boost
Pr 42
Pr
08
Pr
42
Pr 39
Pr + [(freq/Pr ) x (Pr - Pr )]42 39 08 39
2
Output
Voltage
Voltage
Boost
Output
Frequency
Shaft speed
Demanded speed
Load