Mechanical Brake Control - Danfoss VLT AutomationDrive FC 300 Design Manual

Product Introduction
Size
3 3
FC 302
3x380-500 V*
FC 302
3x525-690 V
Table 3.19 Brake Limits
* Power size dependent
NOTICE
Check that the brake resistor can handle a voltage of
410 V, 820 V, 850 V, 975 V, or 1130 V - unless Danfoss
brake resistors are used.
Danfoss recommends the brake resistance R
guarantees that the frequency converter is able to brake at
the highest braking torque (M
can be written as:
R rec Ω =
P motor x M br (%) x η VLT x η motor
η is typically at 0.90
motor
η is typically at 0.98
VLT
For 200 V, 480 V, 500 V, and 600 V frequency converters,
R at 160% braking torque is written as:
rec
107780
200 V : R rec =
P motor
464923
V : R rec =
500
P motor
630137
V : R rec =
600
P motor
832664
V : R rec =
690
P motor
NOTICE
The resistor brake circuit resistance selected should not
be higher than that recommended by Danfoss. D-F size
frequency converters contain more than one brake
chopper and must use one brake resistor per brake
chopper.
NOTICE
If a short circuit occurs in the brake transistor, power
dissipation in the brake resistor is only prevented by
using a mains switch or contactor to disconnect the
mains from the frequency converter. The contactor can
be controlled by the frequency converter.
48
VLT
Brake active Warning Cut out
before cut (trip)
out
810 V/795 V 84 V/828 V 850 V/855 V
1084 V 1109 V 1130 V
. This
rec
) of 160%). The formula
br(%)
U dc 2 x 100
Ω
Ω
Ω
Ω
®
AutomationDrive FC 300 Design Guide 90-1200 kW
WARNING
FIRE HAZARD
Brake resistors get very hot while/after braking, and
must be placed in a secure environment to avoid fire
risk.
3.8.4 Control with Brake Function
The brake is protected against short-circuiting of the brake
resistor, and the brake transistor is monitored to ensure
that short-circuiting of the transistor is detected. A relay/
digital output can be used to protect the brake resistor
against overloading by generating a fault in the frequency
converter.
In addition, the brake makes it possible to read out the
momentary power and the mean power for the latest 120
s. The brake can also monitor the power energizing and
make sure that it does not exceed the limit selected in
2-12 Brake Power Limit (kW). Use 2-13 Brake Power
Monitoring to select what function occurs when the power
transmitted to the brake resistor exceeds the limit set in
2-12 Brake Power Limit (kW).
CAUTION
Monitoring the brake power is not a safety function; a
thermal switch is required for that purpose. The brake
resistor circuit is not earth leakage protected.
Over voltage control (OVC) can be selected as an alternative
brake function in 2-17 Over-voltage Control. This function is
active for all units and ensures that if the DC link voltage
increases, the output frequency also increases to limit the
voltage from the DC link, thereby avoiding a trip.
NOTICE
OVC cannot be activated when running a PM motor
while 1-10 Motor Construction is set to [1] PM non-salient
SPM.

3.9 Mechanical Brake Control

For hoisting applications, controlling an electro-magnetic
brake is necessary. For controlling the brake, a relay output
(relay1 or relay2) or a programmed digital output (terminal
27 or 29) is required. Normally, this output must be closed
for as long as the frequency converter is unable to 'hold'
the motor. In 5-40 Function Relay (array parameter),
5-30 Terminal 27 Digital Output, or 5-31 Terminal 29 Digital
Output, select [32] mechanical brake control for applications
with an electro-magnetic brake.
MG34S202 - Rev. 2013-08-19