Compressor control solutions

Our compressor control solutions are intended for starting, regulation and protection of our industrial piston and screw compressors. All of our control units are built using quality brand-name control and swichgear equipment (Siemens, Moeller, Schneider Electric, Omron, etc.), which is a solid guarantee by itself. The control units perform a multitude of functions which can roughly be divided into three main categories: protection, starting, and regulation.

Every control unit from 30 kW up have an advanced TD Control v1.0 control unit built in which allows for easy adjustment of key parameters, as well as remote monitoring and basic control via a personal computer (the connection is made by means of an RS-232 cable). TD Control brochure can be downloaded here.

PROTECTION

Each of our control solutions comes with the following failsafe elements:

* Short-circuit protection - an appropriately sized circuit breaker is built into every control unit.

* Thermal motor overload - an electronic overload protective device shuts down the compressor if the rated current is exceeded by more than 10%.

* Temperature protection – each compressor is fitted with a temperature sensor which measures the airend temperature and stops the machine in case the Tmax (factory setting) is exceeded.

* Power supply monitoring - the compressor stops in case of a missing phase, inverted phase and undervoltage.

* Each compressor is fitted with a safe-stop control.

MOTOR STARTING

One of the most delicate states of an electromotor is ceratinly starting the motor from zero speed. The main problem is how to overcome the starting torque (breakaway torque) needed to get the load running. Taking this into consideration, the asynchronous motors tend to have a starting current which is much higher than the current stated on the nameplate. As if this was not enough, the starting torque on the shaft tends to oscillate for a while, before settling down.

Having this in mind, and trying to stay shoulder-to-shoulder with modern trends and technologies we decided to develop two variants of our basic control units. One with the traditional wye-delta starters, and the second using electonic softstart devices.

The wye-delta starters have been widely used over the last 30-40 years as a traditional method for compressor starting. The starter consistc of three contactors and a timing relay. The motor is wye-connected in the beginning, which allows for the lower starting voltage (230 instead of 400 V). Once the timing relay trips, the contactors change state, and the motor ends up delta-connected, with full voltage on the stator wounds, allowing it to reach it's nominal working parameters.

Softstart electronic devices are an give us improved possibilities when it comes to motor starting. They use power semi-conductor devices which can be set-up in such a way to allow us to choose the starting voltage and the ramp-up time of the motor. This way we are able to limit the inrush current and reduce the starting torque oscillations.

FULLY AUTOMATED REGULATION

Our new control solutions provide for a fully automated operation of the compressor units.

The 'brain' of the system is a small but powerful programmable relay unit which leaves the factory adequatelly programmed. The control unit is fitted with a large liquid crystal display (LCD) which shows all the relevant parameters, warning and error messages. The traditional pressure-switch regulation is substituted by a pressure transmitter, used for measuring the air pressure. The measurement is registered by the programmable relay which regulates the operation of the compressor accordingly.

For easier orientation, the control units are marked in the following fashion:

US-XXX-Y

where US stands for control unit, XXX is the rated power of the compressor, while the Y position denotes whether the compressor is using a wye-delta starter (YD), or a softstarter (S).

All of our compressors come with the control units built-in (standard YD, S as an option). Control units can also be ordered separately.

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TD Command 4/1 central control unit

TD Command 4/1 is a central control unit for connecting up to four of E1VK line stationary screw compressors. It allows fully automated parallel operation of up to 4 compressors, one of which can be from our VSD line.

The central control unit is based on an industrial programmable logic controller (PLC) with a built-in user program which doesn't need any adjustments after delivery. The front side of the control panel is occupied by a 5,7" touch panel which allows the user to adjust all the necessary parameters in order to fit the working regime to their needs. Besides the touch panel you will also find a serial port (RS-232) which can be used to connect to a personal computer. Once connected you can use our TD Command SCADA software package to remotely monitor and control the unit and log all relevant data.

The main benefits of using a TD Command 4/1 central control unit are:

* Fully automated operation of all of your compressors. The ignition sequence can be set to either manual or automatic operation. In the automatic operation mode the sequence is determined based on the comparison of the compressor's working hours in such way that all of the compressors are equally exploited. If you require an exact sequence all you have to do is switch the control unit to manual mode and choose the correct sequence from a drop menu;

* Full scale SCADA capabilities, which allow remote monitoring, data logging and control. The TD Command 4/1 comes with a free copy of TD Command SCADA software package which can be used after the central control unit has been connected to a personal computer by means of an RS-232 cable. The connectivity has been tested at distances of 300m, while the maximum theoretical distance is L=1200m;

* Adjustable 'on-delay' makes sure that the next compressor is started only after the previous is at full speed, thus eliminating large inrush currents from simultaneous motors starting;

* Easy comissioning. Each compressor requires no more than two wires to connect to the central control unit.

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Adsorption air dryers

Drying of compressed air below relative humidity of 100% is acomplished with two-chamber adsorption dryers. The air is dryed to 0,55 gr/m3 humidity concentration.

Two-chamber system allows continous flow. 8-12% of capacity is used for regeneration process, depending on pressure and temperature. Lower pressures and higher temperatures use larger percent and higher pressures and lower temperatures use smaller percent of air for regeneration.

Type selection:

Adsorption dryers are chosen depending on capacity, working pressure and temperature of inlet compressed air.

Diagram is given for inlet compressed air temperature of 30 °C.

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Cyclonic separators

The purpose of cyclonic separators is to separate liquid and gas phases of the fluid. They are primarily used for separating condensate from compressed air.

Separator is choosed by in accordance with the circulation speed of the fluid. Diagram is related to compressed air inlet temperature 35°C

Example:

V=6 m3/min      F.A.D.

P=10 bar           Working pressure

t=35 °C            Inlet temperature

The nearest size (size 4) is chosen from the diagram according to the calculation.

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Ceramic refiners

Ceramic refiners are used for the finest separation processes, removing even the smallest oil droplets from compressed air. This utilisation of ceramic filters does not eliminate other gases. Liquid phases pre-separating can be used to effectively improve the quality of compressed air. Refiners also eliminate dust and other impurities.

Type selection:

The ceramic refiners are chosen according to the diagram below. The optimal pressure drop over the filter is 0.1 bar approximatelly. The diagram is shown for the air inlet temperature of 35°C.

Example:

V=6 m3/min      F.A.D.

P=10 bar           Working pressure

t=35 °C            Inlet temperature

The nearest type (type KF-4) is chosen from the diagram according to the calculation.

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Compressed air tanks

Basic tank functionality in compressor facilities is to adjust compressed air effective supply according to consumer requirements. Besides this, tank capacity is reducing pressure oscilattions and ensures compressed air requirements in case of instant large air comsumption.

Our air tanks and all other pressure vessel fulfill law requirements about manufacture and exploitation.

The required air tank capacity can be calculated by the following equation:

Vmin=(Po*Qk*Tz)/(4*ΔP*Z*To)     [m3] - required capacity

with symbols denoting:

Po [bar] - atmospheric pressure

Qk [m3/h] - Compressor F.A.D.

Z [1/h] - max. allowed starts/hour

ΔP [bar] - 'on' and 'off' pressure difference

To [°K] - inlet air temperature

Tz [°K] - tank air temperature

Standard tanks have two designs - vertical(S) and horizontal(L). We can also manufacture air tanks for all volumens and pressures per request.

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