Specifications

13 DC TIME (DC BRAKE TIME)

This parameter determines the length of time that the DC braking voltage is applied to the

motor. DC TIME should be set to the lowest value that provides satisfactory operation in

order to minimize motor heating.

Note: If this parameter is set to 999.9 seconds (the maximum value), the DC braking will

be continuous. If it is set to 0.9 seconds, it is disabled.

14 DYN BRAK (DYNAMIC BRAKE)

This parameter enables the dynamic braking circuit. Set this parameter to ON only if the

optional dynamic braking circuit board and resistors are installed.

Dynamic braking is used in applications where high-inertia loads need to be decelerated

quickly. When this is attempted, the motor regenerates voltage back into the drive, causing

the DC bus voltage to rise, eventually resulting in a HI VOLTS fault. With the dynamic

braking option, the DC bus voltage is monitored, and when it reaches a certain level, a

transistor is switched on that connects an external resistor bank across the DC bus. This

allows the regenerated energy from the motor to be dissipated through the resistors as heat,

which keeps the DC bus voltage below the trip level.

16 CURRENT (CURRENT LIMIT)

This parameter sets the maximum allowable output current of the drive, which also

determines the torque capability of the motor. For most applications, CURRENT is left at

the maximum setting, which is 150% or 180% (of the drive’s output current rating),

depending on whether the input voltage is low or high (see Parameter 0 - LINE VOLTS).

Regardless of the CURRENT setting, the drive is capable of delivering a maximum of 150%

current for one minute, and 180% current for approximately 30 seconds, before tripping into

an OVERLOAD fault. See Parameter 17 – MOTOR OL below.

The drive will enter current limit when the load demands more current than the drive can

deliver, which results in a loss of synchronization between the drive and the motor. To

correct this condition, the drive will enter FREQUENCY FOLDBACK, which commands the

drive to decelerate in order to reduce the output current and regain synchronization with the

motor. When the overcurrent condition passes, the drive will return to normal operation and

accelerate back to the speed setpoint. However, if FREQUENCY FOLDBACK cannot

correct the condition and the drive remains in current limit for too long, it will trip on an

OVERLOAD fault. If the drive enters current limit while accelerating, the time required to

reach the speed setpoint will be longer than the time programmed into ACCEL

(Parameter 8).