VLT ® 2000 Series I Control accuracy Basically we distinguish between open loop and closed loop control.When the control is an open loop type the motor current acts as process feedback. The final result is therefore highly dependent on the characteristics of the motor. Note that large motors give a better result than small motors. A closed loop control incorporates a direct process feedback, which substantially improves the control accuracy. The stated maximum torque follows the power hyper- bola in the frequency range across the motor’s rated frequency. How the VLT works Open loop (depending on motor size) ± 2.0 % 3-100 Hz (10-90% of max.
torque) PI (closed loop) ± 0.5% 1.2-100 Hz (-90 - +90% of max. torque) I Programmable control inputs and signal outputs in 2 setups The digital technique used in the VLT 2000 Series makes it possible to redefine the different control inputs and signal outputs and to program 2 different user defined setups. It is easy for the user to program the required functions on the keyboard of the VLT 2000 Series or via the RS 232 user interface. I Galvanic isolation With the VLT 2000 Series safety isolation is standard, as the high-voltage parts of the power section are galvanically isolated from the low-voltage parts of the control section according to VDE 0160/0106 (PELV).
Therefore PCs and the like will not be disturbed. Section 1 Section 2 Section 3 I Advanced motor protection The VLT 2000 Series has a built-in electronic thermal motor protection. The frequency converter calculates the motor temperature on the basis of voltage, current, frequency and time. The thermal motor protection is comparable with a thermal relay in the motor cables. Therefore it is superior to the traditional bi-metallic protection, where the altered cooling conditions due to the speed control are not taken into consideration. I Protection against mains disturbance The VLT 2000 Series is protected against transients arising on the mains, e.g.
when you switch in power factor phase-correction capacitors or when the supply is subject to lightning strikes. Adequate motor voltage and full torque can be main- tained down to 10% under-voltage on the supply mains. I Long motor cables For the VLT 2000 Series motor coils in an IP 00 or IP 10 enclosure are available as modules. This makes it possible to install a long cable between motor and frequency converter. Motor coils are also included in the RFI and motor filter module in IP 20 enclosure. See page 34 for a speciffication of maximum cable length. MG.20.B6.02 – VLT is a registered Danfoss trademark 25