The max. permissible load on the brake resistor is stated as a peak power at a given intermittent duty cycle and can be calculated as:
The brake resistance is calculated as shown:
Rbr
Ω
=
Udc
2
Ppeak
where
P
peak
= P
motor
x M
br
[%] x
η
motor
x
η
DRIVE
[W]
As can be seen, the brake resistance depends on the intermediate circuit voltage (U
dc
).
The AF-650 GP brake function is settled in 4 areas of mains:
Size
Brake active
Warning before cut out
Cut out (trip)
3 x 200-240 V
390 V (UDC)
405 V
410 V
3 x 380-480 V*
810 V/ 795 V
840 V/ 828 V
850 V/ 855 V
3 x 525-600 V
943 V
965 V
975 V
3 x 525-690 V
1084 V
1109 V
1130 V
* Power size dependent
NB!
Check that the brake resistor can cope with a voltage of 410 V, 850 V, 975 V or 1130 V - unless GE brake resistors are used.
GE recommends the brake resistance R
rec
, i.e. one that guarantees that the
frequency converter is able to brake at the highest braking torque (M
br(%)
) of
160%. The formula can be written as:
Rrec
Ω
=
Udc
2
x
100
Pmotor
x
Mbr
(%)
x
η
DRIVE
x
η
motor
η
motor
is typically at 0.90
η
DRIVE
is typically at 0.98
For 200 V, 480 V and 600 V frequency converters, R
rec
at 160% braking torque is written as:
200
V
:
Rrec
= 107780
Pmotor
Ω
480
V
:
Rrec
= 375300
Pmotor
Ω
1)
480
V
:
Rrec
= 428914
Pmotor
Ω
2)
600
V
:
Rrec
= 630137
Pmotor
Ω
690
V
:
Rrec
= 832664
Pmotor
Ω
1) For frequency converters
≤
7.5 kW shaft output
2) For frequency converters 11 - 75 kW shaft output
NB!
The resistor brake circuit resistance selected should not be higher than that recommended by GE. If a brake resistor with a higher ohmic value is selected, the
160% braking torque may not be achieved because there is a risk that the frequency converter cuts out for safety reasons.
NB!
If a short circuit in the brake transistor occurs, power dissipation in the brake resistor is only prevented by using a mains switch or contactor to disconnect the
mains for the frequency converter. (The contactor can be controlled by the frequency converter).
NB!
Do not touch the brake resistor as it can get very hot while/after braking. The brake resistor must be placed in a secure environment to avoid fire risk
AF-650 GP Design Guide
42
3
Summary of Contents for AF-650 GP Series
Page 5: ...AF 650 GP Design Guide 4 1...
Page 53: ...AF 650 GP Design Guide 52 4...
Page 97: ...Please note airflow directions 6 1 5 Mechanical Dimensions AF 650 GP Design Guide 96 6...
Page 98: ...Please note airflow directions AF 650 GP Design Guide 97 6...
Page 99: ...Please note airflow directions AF 650 GP Design Guide 98 6...
Page 100: ...Please note airflow directions AF 650 GP Design Guide 99 6...
Page 173: ...Max cable length 150 m AF 650 GP Design Guide 172 9...
Page 179: ...AF 650 GP Design Guide 178 9...