Eaton M-Max series, Руководство по эксплуатации

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04/10 MN04020001Z-EN
Brake resistors
165
Brake resistors
The MMX34AA3D3… to MMX34AA014…versions of M-Max
TM
series frequency inverters are fitted with an internal brake
chopper. This can be activated at parameter P12.5
(
a page 119).
A brake resistor connected to the power terminals R+ and R- of the
MMX is switched on if the DC link voltage exceeds the value set at
P12.6. The DC link voltage can be read at M1.8.
The brake resistors listed here convert the mechanical brake
energy into heat which occurs during lengthy regenerative
operation or when braking large moments of inertia. The stated
values (P
DB
) of the brake resistors apply to continuous operation.
In many applications, the brake resistors are not loaded in
continuous operation but in short-time operation. The short-time
rating can be calculated from the ratio of the duty factor to
continuous rating. The type related overload factor depends on the
time and design of the resistor:
P
max
= Maximum short-time rating
P
DB
= Continuous rating 100 % with duty factor
ED = Duty factor
t
C
= Cycle time, maximum 120 seconds
The duty factor is stated as a percentage (%) and is calculated with
the formula:
Example:
With a duty time of 48 s and a cycle time of 120 s the ED value
= 40 % and 20 % with a duty time of 8 s and a cycle time of 40 s.
Resistor BR10561K0-T-PF has a continuous rating of 1000 W. At
40 % ED the permissible overload factor is 2.6 (
a fig. 122,
“Overload factors (e.g. BR1…)“). The short-time rating here is
2600 W. At 20 % ED the permissible overload factor is 6 and thus
the short-time rating P
max
= 6000 W.
P
max
F
P
DB
x 100 %
ED [%]
ED [%] =
ED x 100 %
t
C
Figure 121: Duty factor
h
With brake resistor BR3… the permissible overload factor
is around 50 % of the value of BR1… (
a figure 122,
“Overload factors (e.g. BR1…)“).
h In applications compliant with the UL
®
regulations, the
rating data for continuous braking power and the short-
time rating (P
max
) must be reduced by 25 %.
P
DB
t [s]
ED
t
C
( F 120 s)
Figure 122: Overload factors (e.g. BR1…)
P
DB
ED
P
max
1
2
6
1.1
1.25
1.4
1.7
2.6
3.4
10
20
100 90 80 70 60 50 40 30 20 10 5
ED [%]