Digital Acoustics ESBx-110 Especificaciones descargar pdf (Pagina 162)

Control Block Description

ADDvantage-32 PLUS

4-32

4.23 CURRENT LIMIT

This block provides the user with a feature for selecting an automatic taper back of the

drive current limits by two events or using fixed current limits.

The first event, if enabled by P***:BYPASS I2R = ZERO BIT (DEFAULT), prevents

the drive from faulting on a MOTOR (II) T fault. The current limit block accomplishes

this by lowering the current limit when A***:IIR INTEGR is > to 25 counts. The

MOTOR (II) T fault indicates a motor thermal overload condition where the motor

armature current was above 100% for more than the time specified by X***:Thermal TC.

The motor will be allowed to operate at 150% armature current for 60 seconds if the

Thermal TC is set to 60.0 (DEFAULT). The motor could operate up to 200% armature

current, but the MOTOR (II) T fault would occur much sooner than 60 seconds. The user

can increase the Thermal TC value up to a maximum of 3,000 seconds.

The drive will fault on a BRDGE (II) T fault when drive armature current is 150% of the

drive D.C. MAX CONT nameplate current for 60 seconds. This is an Underwriters

Laboratories (UL) mandated fault where the magnitude and time cannot be altered by

users.

When actual motor armature current rises above 110% motor nameplate, IIR INTEGR

will count up from zero when current is rising and count down when current falls below

110%. The IIR INTEGR is used to calculate motor temperature. The rate at which IIR

INTEGR counts is determined by the magnitude of armature current above 100% and the

thermal TC value.

The current limit taper feature can be disabled by setting P***:BYPASS I2R = ONE BIT.

In this nontaper mode, IIR INTEGR will continue counting when motor armature current

is above 110% until it reaches the maximum count of 100 and faults the drive on a

MOTOR (II) T fault.

The second event provides automatic taper back of the drive current limit to prevent

commutation faults due to overcurrenting the armature above base speed. The current

limit should be set below 150% at maximum motor speed to prevent flashovers.

The user can configure the motor current limits using parameters P***:MAX I LIMIT

and P***:MIN I LIMIT. These parameters are defaulted to C***:POS CUR LMT = 100

and C***:NEG CUR LMT = 100 respectively. The user can enter different current limits

by entering a new value for the "C" parameter corresponding to the POS CUR LMT or

NEG CUR LMT. The value is entered as a percentage of the motor nameplate armature

current. It is assumed the user has correctly scaled the motor armature current to the

drive D.C. MAX CONT nameplate current by setting X***:MOTOR IARM.

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Digital Acoustics ESBx-110 Especificaciones Pagina 162