MagneTek News

MagneTek's New Multiplexing System Controls Multiple Motors from Single Drive

[an error occurred while processing this directive]NEW BERLIN, Wis. -- A unique new Multiplexing System, utilizing a combination of advanced hardware and software to provide control of multiple motors from a single variable frequency drive (VFD), is now available from MagneTek Drives & Systems, New Berlin, Wis. The new Multiplexing System can be applied to multi-pump or multi-fan systems wherein system flow or pressure can be satisfied by a combination of constant speed and variable speed operation. The Multiplexing System utilizes special motor sequencing software to enable a single VFD to operate one of several ac motors at variable speed in response to system demand. When demand exceeds the capacity of the one pump or fan, the Multiplexer System transfers the motor from VFD power to ac line power. The VFD then starts the next motor to operate at variable speed. This infinitely variable control range is attained by providing a reliable method of transferring motors to and from VFD control and line power as system demand increases and decreases. The traditional approach to achieving speed control on multiple motor systems has been to install VFDs on each motor, or one very large VFD, sized to handle all motors. Either approach is more costly. MagneTek's Multiplexing System makes it possible to use a single VFD equal to the size of the single largest motor in the system to achieve infinitely variable response to system demand.

The Multiplexer In Action

Using a typical 3-motor system as an example, MagneTek's approach to multiplexing works as follows: When the Multiplexer System is initialized it evaluates the incoming demand signal. With system demand present, the VFD responds by increasing the speed (frequency) of Motor #1 to satisfy the demand. As demand exceeds the capacity of motor #1, the multiplexer enables the smooth addition of Motor #2. During this shift sequence, Motor #1 is transferred to the line and Motor #2 is connected to the VFD. The VFD follows the demand signal until the maximum output for Motor #2 is reached. Motor #2 is also transferred to the ac line and Motor #3 operates on the VFD. Likewise, as demand decreases, the multiplexer motor sequencing software reduces the speed of the motor under the control the VFD. When this motor reaches its preprogrammed minimum speed, the VFD disconnects it and the next lower motor in the sequence is transferred from line power back to the VFD. The VFD's Speed Search Synchronization gives it the capability to sense motor speed and output frequency to capture (connect to) the motor after its release from the line without a significant current surge.

Energy Savings, Reduced Maintenance

MagneTek's Multiplexing System reduces wear on pumps and motors through elimination of across-the-line starts. Additionally, it provides energy savings and accelerated return on investment by reducing demand charges associated with motor inrush current. Built-in bypass circuits enable emergency operation across the line. MagneTek's Multiplexer software includes sequence compensation for a faulted motor to monitor system motor status and bypass failed motors for smooth operation, and automatic lead/lag motor sequencing to ensure equal wear on all system components. Typical Multiplexer applications include HVAC chilled-water circulation systems, fresh water pumping systems, multiple-cell cooling tower fans, multiple compressor, irrigation water and cutting fluid distribution systems for metal cutting. The Multiplexer can interface to an existing process or building control system via an analog input signal (0-5 VDC, 0-10 VCE or 4-20 ma) proportional to 0-100% of the requested output capacity. In the case of a new installation or independent control, a PID software module can be added to receive the control signal via a pressure or flow transducer. The Multiplexer System is available for 2, 3, or 4-motor systems, from 5 through 500 horsepower. NEMA 1, 12 , and 3R enclosures are available. The MagneTek GPD 506 VFD is included. MagneTek Drives products will be on display at the company's booth, Number 5911, at 2001 AHR Expo, Atlanta. The company's drive manufacturing and engin-eering facilities are located in Los Angeles, Cincinnati, Pittsburgh, and Menomonee Falls and New Berlin, Wis.

MagneTek's GPD 506 AC Drive Features English-Language Operator

NEW BERLIN, Wis., -- DATELINE -- The GPD 506, MagneTek's latest generation of special-purpose adjustable frequency AC drives, provides an English-language operator keypad and valuable application-specific features that add significant benefits at no additional cost from previous versions. The GPD 506 features an alpha/numeric English-language operator keypad display in an easy-to-read 16-character two-line format which facilitates input and monitoring of operating parameters. Its MagneTek-designed control board software provides six multi-speed settings and facilitates access to new features including scalable PID feedback with display and KW/Hr display to monitor power consumption. The drive's built-in PID control and power consumption monitoring also eliminate the cost of external signal conditioners and feedback devices. The GPD 506 incorporates expanded dual-bridge 12-pulse rectification, capable of reducing harmonic distortion by more than 90 percent. Enhanced network architecture provides serial communication links to Johnson Controls Metasys, Landis & Staefa, Echelon Lonworks and Modbus. For applications such as centrifugal fans and pumps, the drive features Inverse PID and a new "sleep" function. This function allows certain operations to be blocked out when their demands fall below levels where they produce measurable benefits, then reactivated automatically when needed. Additionally, undertorque detection is provided to alert the operators to conditions including broken fan belts.

The drive's 98 percent efficiency rating extracts additional energy savings from a standard motor through an automatic voltage optimizing algorithm built into the software. The drive features dc injection braking, critical frequency rejection, momentary power loss override, speed search, overtorque and undertorque detection, multi-step speed operation and accel/decel time selection. Protective functions include motor overload, overheat, overcurrent, undercurrent, phase loss and ground fault. As a defacto standard for commercial HVAC applications, the drive's redesigned Bypass option offers several standard configurations. Other common applications include fans, centrifugal pumps, grinders, buffers, low-viscosity mixers, centrifuges, saws and commercial laundry operations. The new GPD 506 is globally compatible, conforming to CE, UL and CUL requirements. It is available in ratings of 208V to 100hp, 230V to 125hp and 460V to 500hp in NEMA 1 and 12 enclosures. 

MagneTek AC Drive Bypass Options Offer Two or Three-Contactor Designs

NEW BERLIN, Wis., -- Bypass Options in two or three-contactor designs are now available for the GPD 506 AC Drive from MagneTek Drives & Systems, New Berlin, Wis. The Bypass Options allow motors to be run from either the AC drive or the AC power line in critical applications requiring continuous operation, including airhandlers, pumps, cooling towers and chillers. Three-contactor Bypass designs allow the drive to be electrically isolated from power for servicing while the motor is running in Bypass mode on the power line. Two-contactor Bypass designs disconnect the drive output but not the input, so that servicing the drive must be deferred until incoming power can be shut off. Choice of two or three-contactor designs lets the customer balance the convenience of isolation against lower price and smaller size.

Three-Contactor Design

MagneTek's GPD 506 three-contactor Bypass features a design which utilizes both input and output drive contactors when total drive isolation is desired. The three-contact bypass features electrically-interlocked contactors, an input circuit breaker with door interlock, thermal motor overload relay, fused control transformer and door-mounted operator devices. It is packaged with the GPD 506 drive in NEMA 1 or NEMA 12 cabinets, and is available in optional NEMA 4 or 3R enclosures. Installation is quick and simple, requiring only three wires in and three wires out. It is available for all 230 and 460VAC 3-phase GPD 506 Adjustable Frequency Drives.

Two-Contactor Design

MagneTek's compact GPD 506 two contactor Bypass utilizes one contactor to connect drive power to the motor and an alternative contactor to connect the Power line to the motor when in Bypass mode. The unique packaging provides a mounting footprint up to 75 percent smaller than comparable bypass packages. The two-contactor Bypass is perfect for installations where both space allotment and operator accessibility are critical. The design also permits user retrofits to existing GPD 506 ac drives in the field. The two-contactor bypass features electrically-interlocked contactors, input fused disconnect with door interlock, thermal motor overload relay, fused control transformer and door-mounted operator devices. It is packaged with a MagneTek GPD 506 ac drive in a NEMA 1 enclosure, and is available in standard 460VAC models from 1 to 25 hp, with higher hp models slated for future release. Both Bypass designs are compatible with a variety of building automation systems, including System 600 Apogee(r) FLN, LonWorks(r) and Metasy(r) N2. An RS-232 port for Modbus(r) RTU is standard, with an RS-485 interface available as an option.

MagneTek is a major supplier of adjustable speed drives, power supplies and lighting products for commercial and industrial use. Drive and Systems manufacturing and engineering facilities are located in Los Angeles, Cincinnati, Pittsburgh, and Menomonee Falls and New Berlin, Wis.

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