What are the common reasons why NA1 breaker cannot be closed?
1. Under-voltage release is not energized or is damaged;
2. Reset button on intelligent controller is not reset (protruded on the panel);
3. The body of drawer-type breaker is not rocked into the connection position;
4. Secondary circuit of drawer-type breaker has bad contact;
5. The breaker fails to store energy;
6. The mechanism interlock actions and breaker has been locked;
7. The control voltage of closed electromagnet is lower than 85% of Us or closed electromagnet is damaged;
8. Wrong connection of wires of user has lead to energized shunt release and tripping of the circuit breaker.
Drawer-type circuit breaker cannot be rocked to the "connection" position; what is the cause?
1. Foreign matter has fallen into the drawer base and stuck the rocking mechanism or the rocking mechanism has jumping chain;
2. The rated current of circuit breaker does not match that of drawer base;
3. The operation is not in place; no "click" from two sides in the drawer base.
what are the common causes for contactor noise?
1. Power voltage is too low;
2. Magnetic system is skewed or mechanically stuck, which causes that the iron core cannot be pulled level;
3. Iron core polar surface is rusted or has foreign matter (such as grease or dust) on it;
4. Short-circuit ring of iron core is fractured.
What are the common causes for damage to the contactor coil?
1. Low power voltage causes that iron core cannot be pulled normally, and the current in the coil will rise sharply, resulting in overheated and burnt coil.
2. High power voltage (> 110% Us) leads to overheated and burnt coil.
3. Foreign matter has fallen into the contactor, which has demagnetized contactor coil and caused too large gap; the magnetic circuit is not closed, the coil is overheated and burnt.
What are the common causes for thermal relay malfunction?
1. Setting current value is set too small;
2. The starting time of motor is too long;
3. The cross-sectional area of connection wire is too small;
4. Strong shock and vibration;
5. Frequent reversible operation and jogging.
Main causes for and solution to the malfunction of residual current circuit breaker:
1. Operating current is selected too small;
When selecting operating current, it should be higher than 2-4 times normal leakage current in circuit. If normal leakage current of the electronic equipment is larger, the equipment on each circuit cannot be too many, and the total leakage current should be lower than the rated non-operating current of RCD. For example, the leakage current of a desktop computer is 3-4mA, so the number of computers connected to 30mA RCD circuit should not be more than five.
2. Improper use of residual current circuit breaker may cause malfunction;
When a three-pole earth residual current circuit breaker is used in a three-phase four-wire circuit, as the normal operating current in neutral line does not go through zero sequence current transformer, residual current circuit breaker will action once single-phase load is started.
Solution: A three-pole four-wire or four-pole residual current circuit breaker must be used for a three-phase four-wire circuit.
3. Grounding of load-side neutral line behind the residual current circuit breaker causes malfunction;
Grounding of load-side neutral line of the residual current circuit breaker will lead normal operating current to the ground through the grounding point, causing malfunction of residual current circuit breaker.
Solution: Connect the grounding wire to the neutral line on the power side of residual current circuit breaker.
4. Leakage current and wire-to-ground capacitive current cause malfunction.
The load-side wire of residual current circuit breaker is long and is laid closely to the ground, and there will be heavy wire-to-ground capacitive current, which may cause malfunction. Or the earth leakage current may be heavy due to decreased insulation of load-side wire, causing malfunction.
Solution: Use residual current circuit breaker with high leakage operating current or raise the wires overhead.