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8
M’Ax Installation Guide
www.controltechniques.com
Issue Number: 6
The drive can supply the rated maximum continuous output current
(FLC) as follows...
Models M’Ax 403 and M’Ax 406: Up to an ambient temperature of
55°C (131°F)
Models M’Ax 409 and M’Ax 412: Up to an ambient temperature of
45°C (113°F); from 45°C to 55°C (131°F), the maximum permissible
continuous output current is reduced to 8.5A and 10.5A respectively.
If the drive is to be used at an altitude in excess of 2000m (6600ft), de-
rating for altitude must be applied to the output current; see Altitude on
page 26.
Make a note of the following values for the model to be used; you will
need to know these later:
•
Maximum intended ambient temperature (T
AMB
max) (required for
calculating the enclosure size later in this chapter)
•
Maximum continuous output current (if this needs to be a de-rated
value)
•
Maximum heat dissipated into the enclosure
Current de-rating
If this precaution is not taken, the output current of the
drive can exceed the maximum permissible value. This
may result in loss of motor control due to excessive
heatsink temperature causing the drive to trip.
2.12
Thermal protection
The power output stage (IGBT bridge) of the drive is protected as
follows:
•
When the heatsink temperature reaches an alarm level the drive
continues operating; the lower line of the display indicates hot as a
pre-warning
•
If the load is not reduced and the heatsink temperature continues to
rise the drive will trip; the lower line of the display indicates O.ht2
Table 2-8
Maximum currents and heat dissipated into the
enclosure (these do not show de-rating for altitude)
2.13
When to use a braking resistor
When an AC motor is decelerated, or the drive is preventing the motor
from gaining speed due to mechanical influences, energy is returned to
the drive from the motor. When this energy is too great for the drive to
absorb, the DC-bus voltage is raised, which increases the possibility of
the drive tripping due to excessive DC-bus voltage.
Depending on the braking requirements, an internal braking resistor
fitted in the drive, or an external braking resistor, can be used for
absorbing the returned energy. The braking resistor is then switched into
circuit by an internal transistor when the DC-bus voltage reaches 780V.
The required value for the braking resistor is determined by the
maximum required braking torque, while the required power rating is
determined by the amount of energy to be dissipated, the duty cycle and
repetition time, as well as the cooling available for the resistor. When the
value and power rating have been calculated, a decision can be made to
use the internal resistor or an external resistor.
It is important that the braking resistor is adequately
rated otherwise the drive could trip due to excessive DC-
bus voltage; braking will then cease, allowing the motor
to coast uncontrolled.
2.14
Braking resistor data
Table 2-9
Internal braking resistor
Table 2-10
External braking resistor
The instantaneous power rating refers to the power dissipated during the
conducting periods (milliseconds) of the braking transistor (this operates
under a form of pulse width modulation during braking). Higher
resistance values require proportionately lower instantaneous power
ratings.
The required average power rating of (and heat dissipated by) the
braking resistor depends on the duty cycle of the application (see 2.17
Braking-resistor example calculations on page 9).
Model
Output current
Maximum heat
dissipated into
enclosure
T
AMB
max.
Maximum
continuous
Maximum
overload
(2 secs.
max.)
Using
internal
braking
resistor
Using
external
braking
resistor
mounted
outside
the
enclosure
M’Ax 403
55
o
C
(131
o
F)
3.5A
7.0A
250W
100W
M’Ax 406
55
o
C
(131
o
F)
6.5A
13.0A
290W
140W
M’Ax 409
45
o
C
(113
o
F)
9.5A
19A
330W
180W
55
o
C
(131
o
F)
8.5A
17.0A
M’Ax 412
45
o
C
(113
o
F)
12.5A
25A
350W
200W
55
o
C
(131
o
F)
10.5A
21A
CAUTION
Value
75
Ω
Operating voltage (V
R
)
780V at switch-on
760V at switch-off
Peak current rating
10.9A
Peak power rating
8.9kW
Maximum continuous braking power
125W
Absolute minimum permissible
value
40
Ω
Operating voltage (V
R
)
780V at switch-on
760V at switch-off
Maximum possible braking current
(through 40
Ω
) (Ib
MAX
)
20.5A
Peak power rating for 40
Ω
16.8kW
Continuous power rating
(See Braking-resistor example
calculations later in this chapter)
CAUTION
