BREAKAGE OF THE PACDRIVE ELAU MC-4 POWER RESISTOR
WHY CAN THE POWER RESISTANCE BE BROKEN?
One breakdown that we recently encountered was the breakage of the power braking resistor in a SCHNEIDER ELECTRIC ELAU PacDrive MC-4 controller. The function of these resistors is to oppose the flow of electric current in a circuit.
When we spoke to our customer to tell them about the failure of their controller, they explained to us that it was a sudden failure, and that suddenly smoke began to come out of the equipment.
An unexpected and rare breakdown in this type of equipment. All of a sudden he had a machine stopped, but fortunately he was able to fix it quickly since they had a replacement PacDrive MC4.
In figure 1 we can see the bad condition of the resistors; one of them split in half.
Main causes that can lead to this type of breakdown
The equipment knows when to activate the braking resistor. When the motor brakes, the braking resistor acts as a generator, releasing an excess of current that it returns to the DC bus.
Cause 1 – the dissipating current is greater than the resistance capacity, causing it to fail.
Cause 2 – Premature ageing. If the resistance receives excess current, in a short time we can age it or wear it out before its time.
Cause 3 – Defective equipment. The wiring, the servomotor or the driver itself may not be in optimal condition and are the cause of the breakdown.
Adjacent damage:
As we can see in figures 2, 3 y 4, the effect of the high temperature caused by the 2 resistors has burned the electronic card where the support of the 2 resistors is attached.
How can we prevent the braking resistor from failing?
One possible solution is to attach a BM-4 Bleeder to the equipment. This bleeder will increase the capacity of our resistance.
Attachment of the OPERATING MANUAL MC-4, information on the BM-4 Bleeder Module.
Good preventive maintenance consists of anticipating possible failures, not only this but also prolonging the useful life of the equipment.
This maintenance is very important since it reduces possible breakdowns at critical moments in production, reduces the number of repairs and can be planned.
Electronic equipment such as the PACDRIVE MC-4 have different electronic components that have limited durability since changes in temperature, accumulation of dirt, humidity, corrosion and hours of work deteriorate these components and their connections.
This deterioration causes an increase in resistance to the flow of current that can distort the actual readings and produce an overheating effect.
