Danfoss VLT series Programming Manual Download

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3.4.2 2-1* Brake Energy Funct.

Parameter group for selecting dynamic braking parameters.
Only valid for drives with brake chopper.

2-10 Brake Function

Option:

Function:

Available selections depend on

1-10 Motor

Construction

[0] Asynchron:

[0] off

[1] Resistor brake

[2] AS brake

[1] PM non salient:

[0] off

[1] Resistor brake

[0]

Off

No brake resistor installed.

[1]

Resistor
brake

Brake resistor incorporated in the system, for
dissipation of surplus brake energy as heat.
Connecting a brake resistor allows a higher DC
link voltage during braking (generating
operation). The Resistor brake function is only
active in frequency converters with an integral
dynamic brake.

[2]

AC brake

AC Brake will only work in Compressor Torque
mode in

1-03 Torque Characteristics

2-11 Brake Resistor (ohm)

Range:

Function:

Size
related

[ 5.00 -
65535.00
Ohm]

Set the brake resistor value in Ohms.
This value is used for monitoring the
power to the brake resistor in

2-13 Brake Power Monitoring

. This

parameter is only active in frequency
converters with an integral dynamic
brake.
Use this parameter for values without
decimals. For a selection with two
decimals, use

30-81 Brake Resistor

(ohm)

2-12 Brake Power Limit (kW)

Range:

Function:

Size
related

[ 0.001 -
2000.000
kW]

2-12 Brake Power Limit (kW)

is the expected

average power dissipated in the brake
resistor over a period of 120s. It is used as
the monitoring limit for

16-33 Brake

Energy /2 min

and thereby specifies when a

warning/ alarm is to be given.
To calculate

2-12 Brake Power Limit (kW)

the following formula can be used.

Pbr,avg W =

Ubr2 V × tbr s

Rbr Ω × Tbr s

2-12 Brake Power Limit (kW)

Range:

Function:

br,avg

is the average power dissipated in

the brake resistor, R

is the resistance of

the brake resistor. t

is the active breaking

time within the 120 s period, T

is the DC voltage where the brake

resistor is active. This depends on the unit
as follows:
T2 units: 390V
T4 units: 778V
T5 units: 810V
T6 units: 943V / 1099V for D – F frames
T7 units: 1099V

NOTE

If R

is not known or if T

is different

from 120s, the practical approach is to
run the brake application, readout

16-33 Brake Energy /2 min

and then

enter this + 20% in

2-12 Brake Power

Limit (kW)

2-13 Brake Power Monitoring

Option:

Function:

This parameter is only active in frequency
converters with an integral dynamic brake.
This parameter enables monitoring of the
power to the brake resistor. The power is
calculated on the basis of the resistance
(

2-11 Brake Resistor (ohm)

, the DC link voltage,

and the resistor duty time.

[0]

Off

No brake power monitoring is required.

[1]

Warning

Activates a warning on the display when the
power transmitted over 120 sec. exceeds 100%
of the monitoring limit (

2-12 Brake Power Limit

(kW)

The warning disappears when the transmitted
power falls below 80% of the monitoring limit.

[2]

Trip

Trips the frequency converter and displays an
alarm when the calculated power exceeds
100% of the monitoring limit.

[3]

Warning
and trip

Activates both of the above, including
warning, trip and alarm.

If power monitoring is set to

Off

[0] or

Warning

[1], the

brake function remains active even if the monitoring limit
is exceeded. This may lead to thermal overload of the
resistor. It is also possible to generate a warning via a
relay/digital output. The measuring accuracy of the power
monitoring depends on the accuracy of the resistance of
the resistor (better than

20%).

Parameter Description

VLT

HVAC Drive Programming Guide

MG.11.CC.02 - VLT

is a registered Danfoss trademark