WEG SSW-08 User Manual - page 45

5

Programming Information and Suggestions

40 | SSW-08

Determine the maximum thermal class:

To correctly program the Thermal Class that will protect your motor it is essential to have in hand 

the motor locked rotor current and locked rotor time. This information is available in the motor 

manufacturer’s catalogue. Put these values into figure 4.8, in case of the cold stall time or into 

figure 4.9, in case of hot stall time.

For example: 

Stall Current = 6,6 x ln 

Hot Stall Time = 6s

6.6 x ln of the motor

t(s)

6 s

0

xln

30

Hot

25

20

Figure 5.11: Checking the maximum class of curves in hot condition

Class 25 is the highest class that protects the motor.

NOTE!

Remember that this protection has as a standard the Three Phase IP55 Standard 

WEG Motor, therefore if your motor is different, then do not program the thermal class 

to its maximum, instead, program it near its minimum thermal class to start.

Example of how setting the thermal class:

Motor data:

Power: 50 hp

Voltage: 380 V

Nominal Current (ln): 71 A

Service Factor (S.F.): 1.00

lp/ln: 6.6

Stall time: 12 s in hot condition

Speed: 1770 rpm