ABB ACS550 Series, Руководство пользователя

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ACS550 User’s Manual 277
Technical data
Brake components
Availability
Braking availability for ACS550 drives, by frame size is:
• R1 and R2 – a built-in brake chopper is standard equipment. Add appropriate
resistor, as determined using the following section. Resistors are available from
ABB.
• R3…R6 – does not include an internal brake chopper. Connect a chopper and a
resistor, or a brake unit to the DC link terminals on the drive. Contact your ABB
representative for appropriate parts.
Selecting the braking resistors (frame sizes R1 and R2)
Braking resistor must meet three requirements:
• Resistance must be always higher than the minimum value R
MIN
defined for the
drive type in the following tables. Never use resistance below this value.
• Resistance must be low enough to be able to produce the desired braking torque.
To achieve the maximum braking torque (the larger of 150% of heavy duty or
110% of nominal duty), the resistance must not exceed
R
MAX
. If maximum
braking torque is not necessary, resistor values can exceed R
MAX
.
• The resistor power rating must be high enough to dissipate the braking power.
This requirement involves many factors:
– the maximum continuous power rating for the resistor(s)
– the rate at which the resistor changes temperature (resistor thermal time
constant)
– maximum braking time ON – If the regeneration (braking) power is larger than
the resistor rated power, there is a limit to the ON time, or the resistor
overheats before the OFF period begins.
– minimum braking time OFF – If the regeneration (braking) power is larger than
the resistor rated power, the OFF time must be large enough for the resistor to
cool between ON periods.
– the peak braking power requirement
– type of braking (deceleration to zero vs. overhauling load) – During
deceleration to zero, the generated power steadily decreases, averaging half
of the peak power. For an overhauling load, the braking is countering an
external force (gravity for example) and the braking power is constant. The
total heat generated from an overhauling load is double the heat generated
from deceleration to zero speed (for the same peak torque and ON time).
Time
Braking ON
Braking OFF
ON time OFF time
Cycle time
Cycle time
ON time
Duty cycle =