The DC brake function serves to induce a direct voltage in the inverter in order to lock the poles of the induction motor and thus brake the motor movement.
The brake function is generally used for deceleration, but it can also be used for acceleration in lifting applications.
To execute the braking function, you need 3 pieces of information:
1 - Percentage of current to be injected
2 – Injection time
3 – Injection start frequency
See the following parameter settings for DC braking.
This parameter defines the level of the DC braking current output (in percent) to the motor during starting and stopping. When you define the percentage of DC braking current, the rated current is considered 100%. Start with a low DC braking current level and slowly increase it until the proper braking torque is achieved. However, to avoid burning the motor, the DC braking current must NOT exceed the rated current. Therefore, DO NOT use the DC brake to replace a mechanical brake, otherwise injury or accident may result.
During acceleration, if the inertia or if the load weight is large, the engine may not have power at the start of the acceleration due to external forces or the inertia of the engine itself. This parameter defines the time that the current will be injected at the motor start (acceleration). This parameter emits DC current, generating torque for force or acceleration to obtain a stable start before motor operation. This parameter determines the duration of the DC braking current output to the motor. Setting this parameter to 0.0 disables DC brake on startup. If you use the inverter with the motor running, it may cause damage to the motor or trip the inverter protection due to excess current.
The motor can keep turning after the deceleration ramp ends, even if the drive has stopped the movement, the motor can keep turning due to external forces or the inertia of the motor itself. This parameter defines the time the current will be injected. This parameter emits DC current, generating torque to force the motor to stop on deceleration.
This parameter defines the time the current will be injected, generating torque to force the drive to stop after the drive stops output to ensure the motor stops. Setting this parameter to 0.0 disables DC brake at stop. If you use the inverter with the motor running, it may cause damage to the motor or trip the inverter protection due to excess current.
This parameter determines the start of the frequency that will be injected into the inverter. When this setting is less than Pr.01-09 (Start frequency), the DC brake start frequency starts at the minimum frequency.
The DC brake sequence diagram is as follows.
Use the DC brake before starting the motor when the load is moving at stop or when there are lifting, fans and pumps. Motor is in free run status and in an unknown direction of rotation before drive starts. Perform DC brake before starting the motor.
Use DC brake at stop when you need to quickly brake the motor or control positioning or when the deceleration force is not enough to stop the motor inertia, such as with cranes or cutting machines.