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VSD Terms and Definitions
The strength of the magnetizing field between the rotor and
stator .Flux density1.
The ratio at which constant torque is provided.2. v IHz ratio
Base frequency3.
4. In-rush current:
The front end section of the VSD, which changes AC to DC.
A diode bridge rectifier, or and SCR rectifier can be used5. Converter
Area of the drive that smoothes the DC voltage before
applying it to the inverter .DClink6.
The last section of the VSD that inverts DC into a variable
frequency and variable voltage signal.
7. Inverter
A silicon controlled rectifier is a three junction, four layer
semiconductor which exhibits the following circuit
characteristics:
8. SCR
.Current can flow from the anode to the cathode when the
voltage exceeds approximately 1 volt (plus to minus) and the
gate lead is made positive with respect to the cathode by a
suitable gate signal.
.Similar to the diode, no current can flow from the cathode
to the anode. ~
.Unlike the diode, the SCR can block current flow in the
forward direction ( snode to cathode) by keeping the gate
negative with respect to the cathode.
Diode9. The diode is a single junction, two layer semiconductor which
exhibits the following circuit characteristics:
.Current can flow from the anode to the cathode when the
voltage exceeds approximately 0.5 volts with the proper
polarity (plus to minus ). ".No appreciable current can flow from the cathode to the
anode regardless of. the polarity or voltage magnitude as
long as the diode is operated within its reverse voltage
rating.
VSD Terms and Definitions
IGBT0. The IGBT is a two junction, three layer device. IGBT's
provide a high switching speed necessary for PWM inverteroperation. IGBT's are capable of switching on and off several
thousand times a second. An IGBT can turn on in less than
400 nanoseconds and off in approximately 500 nanoseconds.
An IGBT consists of a gate"collector and an emitter. When a
positive voltage is applied to the gate of the IGBT, it will turn
on. This is similar to a switch. Current will flow between the
collector and emitter. An IGBT is turned off by removing the
positive voltage from the gate. During the off state, the IGBT
gate voltage is normally held at a small negative voltage to
prevent the device from turning on.
Harmonics: Any waveform that is not equal to the fundamental sinusoidal
waveform is considered to be a harmonic. Terms used to
describe these waveforms are as multiples of the
fundamental. Such as a Sth harmonic is S times the
fundamental.
11.