V/Hz Regulation Mode - Reliance electric GV3000/SE Instruction Manual

V/Hz Regulation Mode

A three-phase motor is normally operated at a constant voltage and at a constant frequency from line
supply. This results in a constant rated torque at a constant speed.
To vary motor speed, motor frequency and motor voltage must be varied. This is achieved by a
frequency inverter. The inverter transforms the constant input quantities into variable output quantities
(output voltage and output frequency vary). The ratio of output voltage to output frequency (Volts/Hz) is
calculated for standard applications as follows:
A constant ratio of voltage/frequency (V/Hz) provides generally a constant motor torque (low speeds
need more voltage to compensate for motor losses). A function generator calculates the motor voltage
based on requested frequency and user selected drive load characteristics.
The inverter consists basically of two sections, the power section and the regulator section:
In the power unit, the line voltage is converted into a DC voltage from which a variable output voltage
with variable frequency is produced by means of power transistor modules. The GV3000 Power Units
are described in manual 49'1327 with block wiring diagrams presented.
In the regulator section, the control of the transistors required for this purpose is produced and
monitored. The PWM signal is produced by software to switch Intelligent Power Modules IPM's to output
three phase motor voltage at requested frequency. The following block diagram presents the basic
linkage of the individual sections. The regulator section can be split into three different modules:
Microprocessors perform in V/Hz regulation mode the Frequency open loop and Voltage Vector loop
tasks of the inverter.
General parameter P.048 provides selection of V/Hz regulation mode.
Refer to Section 4 for - Description of parameter types : 'Configurable' and 'Tuneable'.
Refer to Section 8 for - Parameter Lists Overview,
Section 4 for - General Parameters description, and
Section 3 for - Parameter verification and programming, and password entry.
The following block diagram presents the V/Hz regulation signal flow overview.
The following parameters with this warning sign are safety relevant and must be
adjusted by a qualified person who understands the significance of setting them
accurately. Failure to observe this precaution could result in bodily injury.
49'1329 e
5 - V/HZ REGULATION MODE
(Volts/Hz) = Rated motor voltage / rated motor frequency
Regulator card,
Power Interface and Supply (PIS) card,
Keypad.
GV3000/SE 5 - 1