Hello again

A question, EOL CET 5, tripping on locked rotor current only startups, whether pump has been off for 10 minutes or 24 hours.
Total number of pumps that have had there EOL changed from CET3's to CET5's is 4.
The CET 5's where set at the factory settings of 6 FLA at 10 secs
The motor locked rotor current is 7.5 FLA. application is a slurry centrifugal pump.
We have worked out how to gain access to level 2 and change the FLC to 8 times the only thing is due to the trip curve 5 secs is all we can achieve.
This is the question the acceleration factor TD equals 1?
Changing this constant which way up or down to a max of 1.5 or down to say 0.5, does this increase or decrease the desired time of say 10 to 15 secs to allow the pump to start under load.

Regards

PhilD

Hi PhilD

The CET5 User Manual says to increase the value of TD to allow for a longer than normal start. Please note the warnings it provides that in setting the TD value greater than 1.00 it could subject your motor to locked rotor current for greater than the locked rotor time potentially causing it permanent damage.
The best solution would be to contact the motor manufacturer and find out the actual locked rotor time for that motor and change the setting for locked rotor time.

Regards
Shozza

Hi PhilD,

The CET5 Overload protection uses four parameters to determine the tripping level and thermal rise of the motor, these are full load current (FLA), locked rotor current (FLC), locked rotor time (LRT) and service factor (SF). The TD also varies the tripping time but this is a factor that can either increase or decrease the protection offered to your motor - increasing the TD above 1 will increase your time until trip. If possible I would recommend leaving this at 1.

Often service factor is left at the default level 1.01 which is below what other overloads and motors are generally configured for. Most motors have an in built service factor of 1.05 to 1.2 so setting your service factor at 1.05 or 1.1 will allow you to increase your motor thermal capacity quite safely.

Also, your LRT will determine how long the CET5 takes before it trips during locked rotor conditions, if your LRT is set to 10s then 5s on start up sounds too quick. I would look at checking your phase rotation because the CET5 thermal model is phase sensitive. If you have the phases around the wrong way it calculates the thermal rise too quickly. The easiest way to change this is to change the CET5 phase rotation setting, default is ABC, change this to ACB and see if your thermal rise % calcluates as expected, if it stays at 0% change it back.

Regards,

Leighc

D

Hello

Thankyou for your comments, most of it I fully understand, the phase sequence I'm trying to fathom out how the sequence effects the thermal model.
Unfortunately one of the motors mentioned burn't out today, so much for the EOL protection as the CET5 has replaced all the protection on this drive and it didn't operate. The backup EL1 did trip, taking out the MCC MCB.
There are alot of issues which will need to be rectified, namely the CET5 main relay is not wired into the line contactor, the auxiliary relays are inputs into the PLC which thru the logic disconnect the line contactor plus generate alarms.
Been attached to production we only handle breakdowns, the maintenance should be looking after the installation and commisioning of the CET5's issues.

REgards
PhilD