Danfoss VLT Series Design Manual page 12

1. How to Read this Design Guide
Thermistor:
1
A temperature-dependent resistor placed where the temperature is to be monitored (adjustable
frequency drive or motor).
Trip
A state entered in fault situations, such as when the adjustable frequency drive is subject to an
overtemperature, or when the adjustable frequency drive is protecting the motor, process or
mechanism. Restart is prevented until the cause of the fault has rectified and the trip state is
cancelled by activating reset, or, in some cases, by programming an automatic reset. Trip may
not be used as a personal safety measure.
Trip-Locked
A state entered in fault situations when the adjustable frequency drive is protecting itself and
requiring physical intervention, such as when the adjustable frequency drive is subject to a short
circuit on the output. A locked trip can only be cancelled by cutting off line power, removing the
cause of the fault and reconnecting the adjustable frequency drive. Restart is prevented until the
trip state is cancelled by activating reset or, in some cases, by being programmed to reset auto-
matically. The trip-lock function may not be used as a personal safety measure.
VT Characteristics
Variable torque characteristics used for pumps and fans.
VVCplus
Compared with standard voltage/frequency ratio control, voltage vector control (VVC
the dynamics and the stability, both when the speed reference is changed and in relation to the
load torque.
60° AVM
Switching pattern called 60°Asynchronous Vector Modulation (par. 14-00).
1.1.7. Power Factor
The power factor is the relation between I
and I
The power factor for 3-phase control:
The power factor indicates to which extent the
adjustable frequency drive imposes a load on
the line supply.
The lower the power factor, the higher the
I
RMS
In addition, a high power factor indicates that the different harmonic currents are low.
The adjustable frequency drive's built-in DC coils produce a high power factor, which minimizes
the imposed load on the line power supply.
12
.
RMS
for the same kW performance.
MG.11.B4.22 - VLT
3 ×
1
Power factor
=
I 1 × cos ϕ1 I
= =
I RMS I RMS
2 2
I RMS I I
= + +
1 5
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VLT ® HVAC Drive Design Guide
plus
) improves
U I
×
COS
1 × ϕ
U I RMS
3 × ×
1
since cos ϕ1 = 1
2 2
I I
+ . . +
n
7