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dc drives suddenly get trips and it shows error "low field current." i don't know the reason behind it. Drive is of ABB make.
tnx in advance for your reply
tnx in advance for your reply
Have you tried monitoring the field current output to see if it's dropping below the setpoint?
One way to control the speed of a DC motor is to vary the current applied to the field (the stationary windings) of the motor. As the current is reduced, the speed of the DC motor will increase because the magnetic field strength decreases as the current decreases.
HOWEVER, if the field strength decreases below a minimum level or is lost while the motor is turning it can cause an overspeed condition or an uncontrolled speed, so it's important to "trip" on a low field current.
So, you need to determine what the field current should be, what it is and what it is doing (decreasing, or staying stable), and then you can determine if the drive is properly detecting a low field current or not, and then you can take appropriate action.
The solution may be as simple as a loose connection or termination somewhere in the field wiring.
I'm sorry I couldn't tell you exactly why the drive is detecting a low field current; you will need to do some investigation and data-gathering to do so. But it is important to understand why low field current can be a very bad problem. The drive may be trying to compensate for a weak field by reducing the armature current/voltage and it has reached a minimum value below which it cannot control the speed or voltage/current. And, sometimes this can be injurious to the drive electronics, so it is trying to warn you that there is some problem with motor or the wiring between the motor, or possibly with the source of the field current (drive? or ?).
Again, you need to use an ammeter or the ammeter function of a multimeter (be sure the expected amount of field current does not exceed the meter's maximum current rating) to monitor the actual field current and compare it to motor nameplate rated or the machine configuration.
One way to control the speed of a DC motor is to vary the current applied to the field (the stationary windings) of the motor. As the current is reduced, the speed of the DC motor will increase because the magnetic field strength decreases as the current decreases.
HOWEVER, if the field strength decreases below a minimum level or is lost while the motor is turning it can cause an overspeed condition or an uncontrolled speed, so it's important to "trip" on a low field current.
So, you need to determine what the field current should be, what it is and what it is doing (decreasing, or staying stable), and then you can determine if the drive is properly detecting a low field current or not, and then you can take appropriate action.
The solution may be as simple as a loose connection or termination somewhere in the field wiring.
I'm sorry I couldn't tell you exactly why the drive is detecting a low field current; you will need to do some investigation and data-gathering to do so. But it is important to understand why low field current can be a very bad problem. The drive may be trying to compensate for a weak field by reducing the armature current/voltage and it has reached a minimum value below which it cannot control the speed or voltage/current. And, sometimes this can be injurious to the drive electronics, so it is trying to warn you that there is some problem with motor or the wiring between the motor, or possibly with the source of the field current (drive? or ?).
Again, you need to use an ammeter or the ammeter function of a multimeter (be sure the expected amount of field current does not exceed the meter's maximum current rating) to monitor the actual field current and compare it to motor nameplate rated or the machine configuration.
