GE Industrial Solutions AF-650 GP General Purpose Drive - Manual (Page 17)

NB!
Check that the brake resistor can handle voltages of 410 V, 850 V, 975 V or 1130 V.
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 ηDRIVE x ηmotor
η
motor
is typically at 0.90 η
DRIVE
is typically at 0.98
For 200 V, 480 V, 500 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)
500 V : Rrec =
464923
Pmotor
Ω
600 V : Rrec =
630137
Pmotor
Ω
690 V : Rrec =
832664
Pmotor
Ω
1) For frequency converters Unit Size 1x
2) For frequency converters Unit Size 2x + 3x
If a higher brake resistor resistanse is selected, 160% / 150% / 110% braking torque cannot be obtained, and there is a risk that the frequency converter will cut
out for protection.
If braking is only e.g. at 80% torque, it is possible to install a smaller brake resistor, the size of which can be calculated using the formula R
rec
, no. 1.
NB!
The resistor brake 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 Brake Resistor Design Guide
16
6