Control Techniques Unidrive Installation Manual page 34

Table 5-5 Brake resistor values (R_LVDC) Unidrive SPMA/D
Pr 6.46 48V
Average
Peak
power
Drive power
(Ω) over 60s
(kW)
(kW)
SPMA
1401/2
0.35 11.9 11.9
SPMD
1401/2
SPMD
0.23 18 16.5
1403
SPMD
0.23 18 18
1404
SPMA
1601/2
SPMD
1601/2
SPMD
1603
SPMD
1604
5.3.1
When a braking resistor is to be mounted outside the enclosure, ensure that it is
mounted in a ventilated metal housing that will perform the following functions:
• Prevent inadvertent contact with the resistor
• Allow adequate ventilation for the resistor
For high-inertia loads or under continuous braking, the continuous power dissipated in
the braking resistor may be as high as the power rating of the drive. The total energy
dissipated in the braking resistor is dependent on the amount of energy to be extracted
from the load.
The resistor ratings given in Table 5-4 are calculated for maximum braking power for the
particular drive and operating voltage.
In most applications, braking occurs only occasionally. This allows the continuous power
rating of the braking resistor to be much lower. It is essential, though, that the power
rating and energy rating of the braking resistor are sufficient for the most extreme
braking duty that is likely to be encountered.
Optimisation of the braking resistor requires a careful consideration of the braking duty.
Select a value of resistance for the braking resistor that is not less than the specified
minimum resistance. Larger resistance values may give a cost saving, as well as a
safety benefit in the event of a fault in the braking system. Braking capability will then be
reduced, which could cause the drive to trip during braking if the value chosen is too
large.
Braking resistor: High temperatures and overload protection
Braking resistors can reach high temperatures. Locate the braking resistors so that
damage cannot result. Use cable having insulation capable of withstanding the high
temperatures. It is essential that the braking resistor is protected against overload
WARNING
caused by a failure of the brake control. Unless the resistor has in-built protection, a
thermal overload relay should be fitted. In the event of the resistor becoming overloaded,
the protection device must disconnect the AC and Low Voltage DC supply from the drive.
34
60V
Average
Peak
power
power
(Ω) over 60s
(kW)
(kW)
0.5 12.64 12.64
0.3 21.1 20.5
0.3 21.1 21.1
Brake resistor rating and positioning
www.controltechniques.com
72V
Average
Peak
power
power
(Ω) over 60s (Ω)
(kW)
(kW)
0.6 15.17 15.17 0.7
0.35 26 24.5 0.41 30.25
0.35 26 26 0.41
To be confirmed
Unidrive SP Low Voltage DC Installation Guide
84V 96V
Average
Peak Peak
power
power power
over 60s (Ω)
(kW) (kW)
(kW)
17.70 17.70 0.7 23.11
28.5 0.5 32.5
30.5 30.5 0.5 32.5
Issue Number: 1
Average
power
over 60s
(kW)
23.11
32.5
32.5