ABB Electrical 1SBN010040R1240 Auxiliary Contactor Block

Model Type: CA5-40N Electrical 1SBN010040R1240 Auxiliary Contactor Block

The CT can be wired for residual current to obtain the zero sequence current, and the action time of the earth fault protection can usually be set to a smaller value, e.g. 50ms.

In circuits controlled by contactors, the line current can be set to exceed 4 (or 6.8) times the full load current I in the thermal overload unit.

The earth fault unit is blocked so that the contactor will not be damaged by the inability to break the high current and the fault current will be broken by the back-up fuse.

This blocking function is also used to prevent malfunctions caused by false zero sequence currents during start-up due to saturation of the CT on the circuit.

In order to obtain a high sensitivity, the earth fault current action value is generally rounded to 15...40% of the rated motor current. ...40% of the motor's rated current.

In networks where the neutral point is insulated or earthed via a high impedance, it is recommended to use feedthrough zero sequence current transformers.

The ratio of this type of transformer can be flexibly selected according to the size of the earth fault current and the sensitivity of the earth fault protection.

Due to the small input impedance of the relay, it is possible to use current transformers with very small ratios.

For example, the KOLMA zero sequence current transformer with a ratio of 10/1A is small, but it is generally recommended to use a zero sequence current transformer with a ratio of 50/1A or 100/1A or more.

The setting value of the ground fault unit is generally set to 5...30% of the value of the fully grounded (metallic grounding) fault current, and the value of the ground fault unit is generally set to 5...30% of the value of the fully grounded (metallic grounding) fault current. .30%, action time is 0.5.... .2 seconds.

Phase unbalance unit monitor system current unbalance condition well prevent motor damage due to serious system unbalance or single-phase operation.

The phase unbalance unit should ensure stability under heavy load conditions to prevent false operation, when the motor is running at less than full load current, it is allowed to have a larger degree of unbalance.

The action time of this unit is an inverse time limit characteristic. Dirt phase protection is an independent unit which will operate with a fixed delay of 600s when the phase sequence is wrong.

The unbalance and inverted phase protection units can be independently selected or withdrawn, e.g. the inverted phase unit can be withdrawn from use when the motor is allowed to operate in reverse phase sequence, so that there is no risk of the motor being damaged by a reversal of phase sequence.

In this case there will be no tripping due to motor reversal. The low-current unit is used for out-of-load protection of motors.

The unit is particularly suitable for equipment cooled by a constant flow of liquid, e.g. submersible pumps, where the cooling capacity of the motor is reduced when the flow is interrupted.

In this case the motor circuit will be tripped by the low current unit detecting the well. The start time totaliser is another measure to control the number of starts in a given period of time.

It can be set according to the permissible number of starts provided by the motor manufacturer.