ABB ACS850-04 series, Hardware Manual

Page: 156 / 164

Resistor braking
156
A resistor other than the standard resistor can be used provided that:
• its resistance is not lower than the resistance of the standard resistor
WARNING! Never use a brake resistor with a resistance below the value specified
for the particular drive / brake chopper / resistor combination. The drive and the
chopper are not able to handle the overcurrent caused by the low resistance.
• the resistance does not restrict the braking capacity needed, ie,
where
• the heat dissipation capacity (E
R
) is sufficient for the application, see step 3
above.
Placing the brake resistors
All resistors must be installed outside the drive module in a place where they will
cool and the maximum allowed cable length (10 m [33 ft]) is not exceeded.
Arrange the cooling of the resistor in a way that:
• no danger of overheating is caused to the resistor or nearby materials
• the temperature of the room the resistor is located in does not exceed the allowed
maximum.
Supply the resistor with cooling air/water according to the resistor manufacturer’s
instructions.
WARNING! The materials near the brake resistor must be non-flammable. The
surface temperature of the resistor is high. Air flowing from the resistor is of
hundreds of degrees Celsius. If the exhaust vents are connected to a ventilation
system, ensure that the material withstands high temperatures. Protect the resistor
against contact.
P
max
Maximum power generated by the motor during braking
U
DC
Voltage over the resistor during braking, eg,
1.35 · 1.2 · 415 V DC when supply voltage is 380 to 415 VAC
1.35 · 1.2 · 500 V DC when supply voltage is 440 to 500 VAC
R Resistor resistance (ohm)
P
max
<
U
DC
R
2