Danfoss VTT Series Applications And Installation Manual page 10

Page 10 of 73
M-AI-VT-001-EN Rev.C.1
Introduction
Term
PM Permanent Magnet
Switch off the 3-phase mains until the compressor capacitor bank is discharged – then
Power Cycle
turn the 3-phase mains on again.
Pressure Ratio Is the ratio of discharge pressure/suction pressure in absolute terms.
PWM Pulse Width Modulation
A type of terminal that takes advantage of its resistance features to transform and absorb
REGEN Terminal
electrical power.
Root-Mean-Square, RMS is a statistical measure of the magnitude of a varying quantity.
RMS The effective RMS value of a periodic current is equal to the DC current that delivers the
same average power to a resistor as the periodic current.
Superheat: The sensible heat added to a refrigerant thus increasing its temperature
SH
following evaporation of all liquid vapor.
SI System International, the International System of Units, http://www.bipm.org.
Service Monitor Tools, a PC program provided by DTC. A user friendly way of displaying
SMT compressor data to the user and offer adjustment of predetermined parameters. The user
interface adjusts itself according to the active access level at the compressor.
The condition at which the compressor cannot sustain refrigerant flow through the
Surge impeller. This will result in increased noise level, rapid temperature increase of the impeller
and decrease of absorbed power. This is an undesirable situation that should be avoided.
Turndown ratio refers to the width of the operational range of a device, and is defined
Turndown Ratio as the ratio of the maximum capacity to minimum capacity. For example, a device with a
maximum output of 10 units and a minimum output of 2 units has a turndown ratio of 5.
User The user is defined as integrator, operator, service, and maintenance staff.
Definition