Danfoss VLT AHF 005 Design Guide

If the lead pump has been running at minimum frequency
(f
min
) for a programmed amount of time, with a xed-
speed pump running, the lead pump contributes little to
the system. When the programmed value of the timer
expires, the lead pump is removed, avoiding water heating
problems.
5.4.1.2 System Status and Operation
If the lead pump goes into sleep mode, the function is
shown on the LCP. It is possible to alternate the lead pump
on a sleep mode condition.
When the cascade controller is enabled, the LCP shows the
operation status for each pump and the cascade controller.
Information shown includes:
•
Pump status is a readout of the status for the
relays assigned to each pump. The display shows
pumps that are disabled, o, running on the
drive, or running on the mains/motor starter.
•
Cascade status is a readout of the status for the
cascade controller. The display shows the
following:
- Cascade controller is disabled.
- All pumps are o.
- An emergency has stopped all pumps.
- All pumps are running.
- Fixed-speed pumps are being staged/
destaged.
- Lead pump alternation is occurring.
•
Destage at no-ow ensures that all xed-speed
pumps are stopped individually until the no-ow
status disappears.
5.5
Dynamic Braking Overview
Dynamic braking slows the motor using 1 of the following
methods:
•
AC brake
The brake energy is distributed in the motor by
changing the loss conditions in the motor
(parameter 2-10 Brake Function = [2]). The AC
brake function cannot be used in applications
with high cycling frequency since this situation
overheats the motor.
•
DC brake
An overmodulated DC current added to the AC
current works as an eddy current brake
(parameter 2-02 DC Braking Time ≠ 0 s).
•
Resistor brake
A brake IGBT keeps the overvoltage under a
certain threshold by directing the brake energy
from the motor to the connected brake resistor
(parameter 2-10 Brake Function = [1]). For more
information on selecting a brake resistor, see VLT
®
Brake Resistor MCE 101 Design Guide.
For drives equipped with the brake option, a brake IGBT
along with terminals 81(R-) and 82(R+) are included for
connecting an external brake resistor.
The function of the brake IGBT is to limit the voltage in the
DC link whenever the maximum voltage limit is exceeded.
It limits the voltage by switching the externally mounted
resistor across the DC bus to remove excess DC voltage
present on the bus capacitors.
External brake resistor placement has the advantages of
selecting the resistor based on application need,
dissipating the energy outside of the control panel, and
protecting the drive from overheating if the brake resistor
is overloaded.
The brake IGBT gate signal originates on the control card
and is delivered to the brake IGBT via the power card and
gatedrive card. Also, the power and control cards monitor
the brake IGBT for a short circuit. The power card also
monitors the brake resistor for overloads.
Product Features Design Guide
MG16C302 Danfoss A/S © 11/2017 All rights reserved. 39
5 5

Danfoss VLT AHF 005 Specifications

General

Brand	Danfoss
Model	VLT AHF 005
Category	DC Drives
Language	English