B&C Technologies DI-475 Industrial - Manual (Page 34)

2. Series 154-A11NB OR 25 Drive System Soft Start
The soft start mechanism is simply a voltage-limiting device. Therefore, to be capable
of seeing just what is happening, connect the leads of a voltmeter to connections
T2 and T3, as shown in Figure 1
Initial starting voltage should be 60 percent to 65 percent of motor nameplate voltage.
Soft start time should be approximately 5 to 7 seconds, as indicated in Figure 2
The starting torque is dependent on the instantaneous RPM of the motor, which is
Directly proportional to the voltage the motor receives, as shown in Figure 3,
If the starting voltage is too low, the motor will not have enough torque to turn the
Basket (tumbler). Therefore, it is important that the starting voltage be high enough to
Turn the basket (tumbler) and that the total starting time be short enough to reduce the
Chance of overloading the system and blowing the fuses.
The 60 percent to 65 percent of the nameplate voltage for starting voltage and the 5 to
7 second soft start time were developed by testing with both a fully laded basket
(tumbler) and an empty basket (tumbler). Therefore, any dryer adjusted as stated will
operate properly with any size load up to the rated capacity.
Figure 4 indicates the difference in the starting voltage necessary for
Various size loads between empty and full.