Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 46)

5-28 DESCRIPTION OF OPERATION
1557-UM050F-EN-P – June 2013
Test Modes
The Bulletin 1557 drive is provided with five test modes that are selected by parameter Test Mode in the
Feature Select group. When Test Mode is set to the default value of zero, the drive is in the normal
operating mode. If the value of this parameter is changed when the drive is running, the change will not
take affect until the drive is stopped.
Setting Test Mode to 1 selects the gate test mode. This mode is used to check the thyristor gating with
the medium voltage off. The line converter gating is at the rated line frequency but is not synchronized
with the line voltage and has positive phase rotation only. The machine converter gating is the same as
in normal operation. The output frequency is determined by the speed reference. Both the input and
output contactors must be open and medium voltage must not be applied to the drive.
CAUTION: Application of medium voltage to the drive input or output
when it is operating in gate test mode may cause severe damage to
the drive.
Setting Test Mode to 2 selects the dc current test mode. This mode is used to test the line converter and
to tune the current regulator and the line commutating impedance. In the dc current test mode, the line
converter operates normally but the machine converter gating is modified to gate both the positive and
negative legs in the same phase in order to short-circuit the dc link current through the machine
converter. The short circuit current is slowly rotated among the three phases with overlap between
phases to ensure that an open circuit does not occur during commutation. There is no current in the
motor and the output contactor must be open. The dc current command is set equal to the value
specified by parameter DC Current Test Command in the Current Control Parameters group.
Setting Test Mode to 3 selects the system test mode. This mode is used to test the drive as a system,
including interfaces with external devices such as programmable controllers, without applying power to
the drive or motor. The drive behaves as if it was running normally but all thyristor gating is inhibited.
Since the input, output, and bypass contactors operate normally in this mode, the drive cannot prevent
medium voltage being applied to the drive or motor and other measures must be taken to ensure that this
does not occur.
CAUTION: It is the responsibility of the operator to ensure that the
drive and motor are isolated from medium voltage when the drive is
operating in system test mode with the input, output, and bypass
contactors closed.
Setting Test Mode to 4 selects the open circuit test mode. This mode is used to test the drives at rated
output voltage and frequency without connecting it to a motor. In open circuit test mode, ac current
sufficient to produce rated voltage at the drive output is forced through the output filter capacitors. When the
drive is started in this mode, it ramps up to rated frequency and synchronizes its output voltage with the line
voltage. The current reference is set to a value that will produce approximately rated voltage at the drive
output. The output voltage can be changed by adjusting parameter Flux Command Base Speed.
CAUTION: Open circuit test mode should not be used when the
drive is connected to a load unless an output contactor is provided.