SSD 605C Product Manual - High Starting Torque

Application Notes  

13-5

605C Frequency Inverter

High Starting Torque

Applications requiring high motor starting torque (greater than 100% of rated torque) need

careful setup of the drive voltage boost feature. For most motors, a FIXED BOOST parameter

(FLUXING function block) setting of 6.0% is usually adequate. Setting the FIXED BOOST

parameter level too high can cause the drive current limit feature to operate. If this occurs, the

drive will be unable to ramp up in frequency. The LIMITING diagnostic (CURRENT LIMIT

function block) will indicate TRUE when the current limit feature is operating. Simply reducing

the level of the FIXED BOOST parameter will remove this problem. It is important to use the

minimum level of FIXED BOOST necessary to accelerate the load. Using a level of FIXED

BOOST higher than necessary will lead to increased motor heating and increased risk of drive

overload.

Note:  Motor torques greater than 100% require high currents to be drawn from the drive. Thus,

the MOTOR I LIMIT parameter (CURRENT LIMIT function block) will have to be set

accordingly such that the drive current limit feature will not activate when accelerating the

load.

The best motor starting performance can be achieved by setting up the SLIP COMP function

block, refer to Chapter 6: SLIP COMP. Also setting the BASE VOLTS parameter (VOLTAGE

CONTROL function block) to 115.4% and the SWITCHING FREQ parameter (PATTERN

GEN function block) to 3kHz, can help to start difficult loads in the most extreme cases.