Quench Vacuum Furnaces offer power management option.
May 30, 2008 -
To cut electrical consumption, High Pressure Quench Vacuum Furnaces feature power management option, which creates single system of alternate control of heating and cooling processes using single frequency converter. Programmable cooling rate is controlled according to load temperature. Offering martempering quench capability, system works with various cooling gases and provides step-less control of heating and cooling power.
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|Original Press release |
Seco/Warwick Corporation USA
180 Mercer St.
Meadville, PA, 16335
Power Management System for High Pressure Quench Vacuum Furnaces
Patent US 7,193,188 B2 - System Saves Over 20% in Energy Costs
SECO/WARWICK has recently patented a power management option (US 7,193,188 B2) for high pressure quench vacuum furnaces that reduces electrical consumption by creating a single system of alternate control of the heating and cooling processes using a single frequency converter. Since issuing the patent in May of 2007, more than 10 Vacuum HPQ systems are in successful operation utilizing this power management system. The sophisticated system results in a minimum of 20% reduction in electrical consumption and improves efficiency by increasing the heating and cooling systems power factor. The system has many operational benefits:
o Step-less control of heating and cooling power
o Programmable cooling rate controlled according to the load temperature
o Martempering quench capability
o Works with various cooling gases
o No blower motor start-up overcurrent, fewer electrical components
o Field operating results demonstrate a minimum of 20% savings in electrical consumption in addition to reducing equipment and maintenance costs
Janusz Kowalewski, VP Vacuum Systems, and the inventor, Maciej Korecki, Director of Research & Development for SECO/WARWICK are available to give a presentation on this new concept along with case studies.
In vacuum furnaces, a system of infinitely variable adjustment of the power of resistance heating elements is based on a three-phase silicon controlled rectifier (SCR) or a variable reactance transformer (VRT). An SCR connected to the electrical supply, controls the power following a control input from a programmable temperature controller, through alteration of the effective output voltage as a result of switching on and off full cycles of sinusoidal supply voltage (proportional-time control or group control, where mean output voltage U is proportional to supply voltage U.sub.n and switch-on time T.sub.z and inversely proportional to period T; U=U.sub.n.times.T.sub.z/T), or through partial clipping of the sinusoidal supply voltage (phase control).
A variable reactance transformer (VRT) adjusts the power following a control input from the control system, through alteration of the effective output current resulting from the impact upon the VRT control circuit current.
In a standard vacuum furnace, the cooling process is not controlled, and the operation of the cooling gas blower motor (3-phases, induction motor) forcing gas circulation through the workload is not adjustable. The motor works to standard working parameters dependent on the load and is connected directly to electrical supply. In the case of motors whose power exceeds a few dozen kW, soft-start systems are used in order to reduce the starting current (and only that). Some designs provide for a two-speed motor featuring a 2:1 ratio of rated rotations of high and low speeds and, consequently, a 4:1 ratio of rated power, which enables motor operation at two rotational speeds and powers as well as diversification of cooling rate: slow cooling at low speed and rapid cooling at high speed.
The latest designs call for full control of the workload cooling process (workload temperature) following an input signal from the temperature controller through adjustment of the cooling blower motor rotational speed within 0 100% (or even more) of rated speed. This is made possible by inverters known as frequency converter which adjust the rotational speed of a 3-phases induction motor by modulating the effective voltage and its frequency or phase. Performance characteristic of a blower motor prevents independent control of rotational speed, power and torque of the motor since a change to any of these parameters entails automatic change of the remaining ones and, effectively, control of rotational speed of an induction motor results in a change of its power or torque. In such a case the motor is wired to the frequency converter's output through a contactor. The frequency converter is supplied from a three-phase supply mains and transforms this energy into three-phase supply of the motor of proper voltage-frequency characteristic, thus enforcing the requested rotational speed and output power or torque.
The purpose of this system is to create a single system of alternate control of heating and cooling processes which would be controlled by a single frequency converter whose output, through contactors, are simultaneously connected: the heating system and the cooling system. The heating system incorporating resistance heating elements is actuated by the heating system contactor. The system may contain a transformer which can adjust voltage if required by the heating elements. The transformer is wired between the heating system contactor and the resistance heating elements.
The cooling system blower is actuated by the blower motor contactor which may also incorporate a transformer to adjust the voltage as needed by the blower motor. The heating and cooling system contactors are connected to the output of the frequency converter and are controlled by the temperature controller.
An advantage in this application would be to have the rated current of the heating and cooling systems comparable at the ratio of 0.33 3 in both systems. Similarly, the rated supply voltage for the heating and cooling systems should be comparable at the 0.33 3 ratio of the rated supply voltage for both systems.
Application of a single frequency converter allows alternate control of the heating system and the cooling system while temperature control is on.
SECO/WARWICK Worldwide manufactures industrial heat processing equipment including heat treat furnaces, vacuum furnace technology, atmosphere generators and aluminum reverb melting and holding systems. SECO/WARWICK provides heat treating equipment and services worldwide for customers involved with primary aluminum, aluminum recycling, automotive, aerospace, commercial heat treating, HVAC, electronics, lighting, medical equipment and nuclear applications.
The globally integrated organization includes SECO/WARWICK Corp. (USA), Retech Systems LLC (USA), SECO/WARWICK S.A. (Poland), ELTERMA S.A. (Poland), SECO WARWICK Allied Pvt. Ltd. (India) and SECO/WARWICK Industrial Furnace Co. Ltd. (China).
The company has over 1000 employees worldwide, and is an industry leader in industrial heat processing equipment and processes. More information can be found at www.secowarwick.com.
Beth Ryan, Director