Motors inverter

DATA BOUNDARY Pumps, MOVs, batteries, chargers, inverters, motors, and... 

Capacity control of these compressors is achieved by varying the compressor speed by means of an inverter motor. 

Availability of micro-computers for intelligent control and protection of the rectifier-inverter motor system. 

Boost converter Bidirect. Converter Bidirect. Converter Inverter Motor... 

In Europe the main motor is usually an AC motor, using a star-delta starter. An inverter for the main motor is becoming more common, particularly with the smaller decanters. The inverter enables a soft start, and allows speed adjustment for different process requirements. Inverter motors can cause unwanted electrical interference, and harmonic wave forms, on the main electrical supply lines. These problems can be minimised by using electrical filters and the latest advanced electrical technology. 

The main component of the back-drive assembly can be an eddy current brake, inverter motor or a DC motor. The Viscotherm Rotodiff hydraulic conveyor drive is a variable speed device, powered by a fixed speed hydraulic motor. 

Conventional back-drive systems on decanters perform a braking duty. As such many of them have the ability to regenerate power. Although an eddy current brake is unable to do this. AC. DC. and inverter motors, and hydraulic systems are. The braking process causes the electric motor to act as a generator and so returns power to the grid. In the case of the DC and inverter motor, the power regenerated is usually considered dirty unless electric filters are fitted which smooth out unwanted harmonics. 

Inverters make it possible to control a variable-speed fan by changing the frequency modulation. Standard alternating-current fan motors may be speed-regulated between 0 and 60 Hz. In using inverters for this apphcation, it is important to avoid frequencies that would result in fan critical speeds. 

The average prices of the batch centrifuge are shown in Fig. 18-154. All the models include the drive motor and control. In Fig. 18-154, the inverting filter, horizontal peeler, and the advanced vertical peeler are the premium baskets especially used for specialty chemicals and pharmaceuticals. Control versatility with the use of programmable logic control (PLC), automation, and cake-heel removal are the key features which are responsible for the higher price. The underdriven, top-driven, and pendulum baskets are less expensive with fewer features. 

A converter unit is used for the control of d.c. machines and also to provide a d.c. source to an inverter unit controlling an a.c. machine. In d.c. drives the d.c. voltage after tlie converter unit should be variable, whereas for in a.c. drive it is kept fixed. The voltage is varied by the invener unit. A convener unit is the basic power conversion scheme to convert an a.c. supply to a d.c. supply. Conventionally they are also known us rectifier units and c in be arranged in four different modes to suit dilTerent applications of a motor as follows ... 

The above tiiethod is used to vary Ihe frequency and the voltage of the inverter output (motor side) according to the process needs, irrespective of Ihe electronics scheme adopted to obtain the required speed control. 

This is Ihe most commonly used inverter for Ihe control of a.c. motors and is shown in Figure 6.28(a). The fixed d.c. voltage from the uncontrolled rectifier converter acts as a voltage source to the inverter. The voltage in Ihe inverter unit is varied to Ihe required level by using a pulse width modulation, as noted earlier. Through Ihe switching circuit of Ihe inverter Ihe frequency of the... 

In addition to the above inverter systems there is one more system, called a cyclo converter system. These drives tire employed for very large motors, when IGBTs in such ratings are a limitation. It converts the fixed a.c. supply frequency to a variable frequency, generally lower than rated, directly and without rectifying it to a d.c, source. They are basically frequency converters. This system is more complex and expensive and has only... 

A power diode reetifier unit feeding a fixed d.e. power to an inverter unit to control an a.c. motor, or a thyristor rectifier unit, directly controlling a d.e. motor, both contain... 

With this technology it is now possible to achieve extremely accurate speed control of the order of 0.01 % to 0.001 %. To achieve such high accuracy in speed control, closed-loop feedback control systems and microprocessor-based control logistics can be introduced into the inverter control scheme to sense, monitor and control the variable parameters of the motor to very precise limits. 

The inverter may be a current source inverter, rather than a voltage source inverter (.Section 6.9.4) since it will be the rotor current that is required to be vtiried (equation (1.7)) to control the speed of a wound rotor motor, and this can be independently varied through the control of the rotor current. The speed and torque of the motor can be smoothly and steplessly controlled by this method, without any power loss. Figures 6.47 and 6.48 illustrate a typical slip recovery system and its control scheme, respectively. 

The pay-off roll is unwound by the tension of the sheet, caused by the speed of the recoiler at the finishing line and the bridles positioned at different locations. The pay-off roll motors therefore operate in a regenerative mode and can feed-back the energy thus saved to the source of supply, if desired. This can be done by using a full-wave synchronous inverter, as shown in Figures 6.31 or 6.33. 

---