Danfoss VLT 5001, VLT 5011 Installation guide
VLT® types 5001-5011
■ Description of the brake system ...................Page 3
■ Application - conveyor belt ........................... Page 3
General formulas ........................................... Page 4
Brake performance examples ......................Page 4
■ Selection of brake resistor ............................Page 5
■ How to setup the brake function ..................Page 6
Basic setup ...................................................Page 6
Power monitoring ..........................................Page 6
Brake check .................................................Page 7
Protection properties ....................................Page 7
Readout of brake power...............................Page 7
DC hold ......................................................... Page 7
■ Installation .....................................................Page 7
Mechanical ................................................... Page 7
Electrical ....................................................... Page 8
EMC (twisted cables/shielding) ................. Page 8
■ Dimensions ................................................... Page 9
Warning:
Do not touch the brake resistors
during braking. They can be very
hot.
MI.50.S1.02 – VLT is a registered Danfoss trademark 1
VLT® types 5001-5011
■■
Introduction
■
■■
The flatpack brakeresistors for the VLT 5000 series is
a safe and compact solution for the customer.
At a constant load and free convection the resistor is
selfprotecting as a fuse. This means short circuit
proof, no fault to frame, no melting of casing and self
extinguishing. The casing is made of anodized
aluminum and is IP54 tight.
■■
Description of the brake system
■
■■
When the speed of a frequency converter is reduced, the motor acts as a generator and brakes.
When a motor acts as a generator, it supplies energy
to the intermediate circuit in the frequency converter.
The brake resistor loads the intermediate circuit, ensuring that the brake power is absorbed by the
brake resistor.
If a brake resistor was not used, the intermediate circuit voltage of the frequency converter would continue to increase, until it cuts out for protection.
The advantage of using a brake resistor is that it
enables braking of heavy load quickly, e.g. on a conveyor belt.
With the compact flatpack resistor, it is possible to
mount the resistor on the rear of a VLT 5000
bookstyle frequency converter.
In addition, VLT5000 incorporates brake monitoring
to ensure that the average power dissipated to the
brake resistor does not exceed a given limit. The
brake monitor calculates the mean brake power
within the last 120 seconds and compares this
value with a programmed limit. If the limit is exceeded the drive can give a warning or trip. Monitoring of short circuiting of the brake resistor or
brake IGBT and disconnection of the brake resistor
is also possible.
Increased performance at low speeds can be
achieved by using the DC brake in VLT5000.
Application - conveyor belt
■■
■
■■
The brake resistor program covered in this instruction
is for horizontal conveyor applications. The resistors
are chosen for use with small drives, this means up
to VLT5011.
The premises for the application is:
● The energy of the system is assumed to be deter-
mined by two times the motor inertia.
● Values for braking are calculated at 160% torque.
Figure 1 shows the relation between the braking
power and the acceleration/braking of the conveyor
belt. During braking the motor power is negative,
since the torque on the motor shaft is negative. The
braking power is to be dissipated in the brake resistor, and corresponds almost to the negative motor
power taking the losses into the motor and VLT frequency converter into account.
Figure 1
Typical characteristic of a
horizontal brake application
MI.50.S1.02 – VLT is a registered Danfoss trademark 3
■■
■
■■
General fomulas
The general formulas for calculation of the brake in a
system are stated below.
An example is shown with the following values:
Motor inertia: j = 0.0021 kgm2
Motor speed (at 50 Hz): n = 1500 rpm
Average power dissipated in resistor: P
Nominal motor power: P
average
= 750 W
motor
= 120 W
The kinetic energy in the system is:
2
E = ½ × j' × ω
= j × ω2 = 0.011 × j × n2 [Ws]
E = 0.011 × 0.0021 × 1500 × 1500 = 52 Ws
2
j = inertia of motor and gear box (kgm
]
j' = inertia of the system ≈ 2 × j
ω = motor speed = (n × 2 × π)/60 [rad/s]
n = motor speed [rpm]
The maximum number of stops per time unit
for the resistor is calculated as:
f
= P
stop
resistor/Esystem
f
= 120/52 = 2.3 s-1 = 138,5 min
stop
[s-1]
-1
VLT® types 5001-5011
The minimum time for stop is calculated as:
= E
t
stop
t
= 52/750 = 0.069 s
stop
P
motor
The maximum duty cycle of the system is:
Duty cycle = t
Duty cycle = 0.069 × 2.3 × 100 = 16%
The resistor values must be calculated using the formulas from the general brake instruction (resistance
based on minimum acceptable resistance). When
choosing a standard resistor, it is necessary to
choose a value higher than the calculated
240 Volt units: R
500 Volt units: R
system
/ P
motor
[s]
= nominal motor power (100% torque)
× f
stop
× 100 [%]
stop
= 111684 / P
rec
R
= 111684 / 750 = 149
rec
= 478801 / P
rec
= 478801 / 750 = 638
R
rec
motor
motor
[Ω]
[Ω]
t
.
rec
Ω
Ω
P
= Average power dissipated in the resistor [W]
resistor
■■
■
■■
Brake performance examples
The figures below show typical data for a horizontal
application. At other frequencies please use the for-
All are calculated at a nominal motor speed of
1500 rpm at 50 Hz.
mulas above to calculate the values.
P
, 120 W
average
VLT type Motor Motor System E (50Hz) Number of E (100 Hz) Number of Stop time [s] Stop time [s]
5001 0.75 0.00210 0.00420 52.0 138.5 207.9 34.6 0.069 0.277
5002 1.1 0.00320 0.00640 79.2 90.9 316.8 22.7 0.072 0.288
5003 1.5 0.00430 0.00860 106.4 67.7 425.7 16.9 0.071 0.284
5004 2.2 0.00690 0.01380 170.8 42.2 683.1 10.5 0.078 0.311
5005 3 0.00820 0.01640 203.0 35.5 811.8 8.9 0.068 0.271
5006 4 0.01200 0.02400 297.0 24.2 1188.0 6.1 0.074 0.297
5008 5.5 0.01800 0.03600 445.5 16.2 1782.0 4.0 0.081 0.324
5011 7.5 0.02300 0.04600 569.3 12.6 2277.0 3.2 0.076 0.304
P
average
VLT type Motor Motor System E (50Hz) Number of E (100 Hz) Number of Stop time [s] Stop time [s]
4 pol. inertia inertia Ws stops 1/min Ws stops 1/min (50 Hz) (100 Hz)
kg
× m × m kg × m × m from 50 Hz. from 100 Hz. 160 % torque 160% torque
, 250 W
4 pol. inertia inertia Ws stops 1/min Ws stops 1/min (50 Hz) (100 Hz)
kg
×
m × m kg × m × m from 50 Hz. from 100 Hz. 160 % torque 160% torque
5001 0.75 0.00210 0.00420 52.0 254.0 207.9 63.5 0.069 0.277
5002 1.1 0.00320 0.00640 79.2 166.7 316.8 41.7 0.072 0.288
5003 1.5 0.00430 0.00860 106.4 124.0 425.7 31.0 0.071 0.284
5004 2.2 0.00690 0.01380 170.8 77.3 683.1 19.3 0.078 0.311
5005 3 0.00820 0.01640 203.0 65.0 811.8 16.3 0.068 0.271
5006 4 0.01200 0.02400 297.0 44.4 1188.0 11.1 0.074 0.297
5008 5.5 0.01800 0.03600 445.5 29.6 1782.0 7.4 0.081 0.324
5011 7.5 0.02300 0.04600 569.3 23.2 2277.0 5.8 0.076 0.304
4
MI.50.S1.02 – VLT is a registered Danfoss trademark
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