With the UNI1405 configuration, the volts / frequency ratio must be kept constant to ensure rated torque is available from the motor over the frequency range. At low frequencies (from 0 Hz to ½ x Pr 5.06) the voltage is increased from this characteristic by a level governed by either the voltage boost parameter or the motor parameters (found during the stator resistance test) depending on whether the drive is in fixed boost or open loop vector mode as shown aside.
UNI1405 Motor Rated Power Factor
The power factor is found by the UNI1405 4kw during the autotune procedure. It is used in the open loop vector algorithm and to set the current limit levels for the torque producing (active) current.
Emerson UNI1405 4kw Motor Rated Speed
The motor rated speed parameter should be set to the synchronous speed of the motor minus the slip speed. This is often displayed on the motor nameplate. I.e. For a typical 18.5 kW, 50 Hz, 4 pole motor the motor rated speed is 1465 rpm. The synchronous speed for a 4 pole motor is 1500 rpm therefore the slip speed is 35 rpm Synchronous speeds for different numbers of poles are as follows:
2 pole = 3,000 rpm
4 pole = 1,500 rpm
6 pole = 1,000 rpm
8 pole = 750 rpm
The accuracy of this parameter is very important as it directly affects the torque produced at the shaft. Often the value given on the motor nameplate is not
Joe Kaminski is an industrial automation specialist at MRO Electric. He has a background in industrial engineering and supply chain management. Joe has worked in the automation industry for over 10 years providing support to some of the largest companies in the world. For more info, visit www.mroelectric.com.