 |
|
|
||||||||||||
|
||||||||||||||
|
|
 Q. What is a constant voltage power conditioner? A. Although a constant voltage power conditioner (sometimes referred to as constant voltage transformer or voltage regulator) is a transformer like device, its design and function are totally different. The function of a constant voltage power conditioner is to provide a voltage across its secondary terminals within a specified tolerance (usually ±5%) as long as the voltage impressed on the primary is within the specified bandwidth (usually +10% to -20%). See the Power Conditioning section for more information. Q. What are the differences between Sola power conditioners? A. All three of these products use Sola's patented ferroresonant technology. The primary design considerations for the CVS series were voltage stabilization and magnetic isolation. This group provides ±1% output voltage regulation with an input voltage range of +10%/-20% with moderate (1000:1) normal (transverse) noise attenuation. The MCR series was designed to address both voltage regulation and magnetic isolation. This group offers ±3% output regulation with an input range of +10%/-20% but also offers magnetic isolation for excellent 1,000,000:1 common mode and 1000:1 normal (transverse) mode attenuation. The MPC series incorporates all of the benefits of the MCR series in addition to exceeding the low leakage current requirements of UL 544 and providing identifiable output receptacles to indicate they are safe for hospital grade use (orange with green triangles). The iSOLAtron™ is an isolation transformer with special filtering to provide an extremely clean ground reference. Although it contains some isolation from noise and surges, it does not regulate the input voltage for swell and sag protection as in the CV, MCR and MPC series. The Three Phase power conditioners utilize microprocessor-based tap switching technology to provide ±5% regulation in three phase installations. The CV, MCR and MPC are single phase only. Q. Can constant voltage power conditioners be used to power motor loads? A. Care needs to be exercised when constant voltage power conditioners (CVPC) are used to power motor loads. When a motor is energized, the lock rotor amperage required to get the motor started is normally 6 to 8 times the normal running amperage, or 600-800% of the load. When the load is increased beyond the CVPC's rated value, a point is reached where the output voltage suddenly collapses and will not regain its normal value until the load is partially released. Under direct short circuit, the load current is limited to approximately 150-200% of the rated full load value and the input watts to less than 10% of normal. Therefore, under short circuit conditions, the Sola CVPC actually runs cooler than at no load. A constant voltage power conditioner, such as the MCR, will protect both itself and its load against damage from excessive fault currents. Fusing of load currents may not be necessary. The actual value of short-circuit current varies with the specific design and rating. Units may be operated indefinitely at short-circuit. This characteristic protects the unit itself as well as the load and load circuit being served. Typical overload performance is shown in the load current chart below (Figure 1).
To properly size a constant voltage power conditioner for use with a motor, be sure to size the CVPC so the nameplate rating is equal to or greater than the lock rotor requirement of the motor. Q. Are there any special considerations needed when I select a constant voltage power conditioner? A. Special consideration must be given to the type of load to be powered (inductive loads need to be sized to start up currents), load power factor, ambient temperature and where the unit will be installed. Q. What exactly is Ferroresonance? A. Ferroresonance is the principle behind Sola's very popular CVS, MCR and MPC power conditioners. Ferroresonance is the property of a transformer design in which the transformer contains two separate magnetic paths with limited coupling between them. The output contains a parallel resonant tank circuit and draws power from the primary to replace power delivered to the load. Note that "resonance" in ferroresonance is similar to that in linear circuits with series or parallel inductors and capacitors, where the impedance peaks at a particular frequency. In a nonlinear circuit, such as Sola's ferroresonant transformers, "resonance" is used to reduce changes in supply voltage to provide a more consistent voltage to the load. A magnetic device is nonlinear. Its reluctance changes abruptly above a certain magnetic flux density. At this point, the magnetic device is defined as being in saturation. The design of the Sola transformer allows one magnetic path (the resonant path) to be in saturation, while the other is not (See Figure 2). As a result, further change in the primary voltage will not translate into changes in the saturated or secondary voltage and voltage regulation results.
Q. How reliable is ferroresonant technology? A. The MTBF (mean time between failures as measured in accordance with Mil. Std 217E) ranges from 10 to 25 years, depending on the model, with typical life being approximately 50 years. All Sola Constant Voltage Power Conditioners are backed by our exclusive 10 + 2 warranty. Q. Is there any problem with phase shift between the input and output voltages of constant voltage power conditioners (CVPC)? A. The phase difference which exists between input and output voltages is in the range of 120 degrees to 140 degrees at full load. This phase differences varies with the magnitude and power factor of the load, and to a lesser extent, with changes in line voltage and load power factor. Q. We have experienced some temperature problems with other makes of power conditioners. Has Sola addressed this problem? A. Sola's ferroresonant power conditioners are very stable with respect to temperature. The change in output voltage is only 0.025% per degree centigrade. Units are factory adjusted to +2%/-0% of nominal, with full load and nominal input voltage. This adjustment to the high side of nominal is to compensate for the natural temperature drift of about 1% that takes place during initial turn on or warm up. When the unit warms up to operating temperature, the voltage typically falls about 1%. This is why no load "cold steel" voltage measurements may be slightly on the high side. At a stable operating temperature, the output voltage will change slightly with varying ambient temperatures. This shift is equal to approximately 1% for each 40oC of temperature change. The normal maximum temperature rise of a Sola power conditioner may fall anywhere in the range of 40oC to 110oC depending on the type and rating. The nominal design ambient rage is between -20oC and +50oC. (-20oC to +40oC for 70 to 1000 VA, 60 Hz portable models.) Q. Will harmonic currents affect ferroresonant power conditioners? A. A Sola ferroresonant power conditioner will have essentially harmonic-free output because of the addition of a neutralizing coil. This coil neutralizes the harmonics in a manner best explained by first considering the device as a conventional transformer with the neutralizing coil disconnected. Though this coil is now open circuited, it has a voltage induced in it as a portion of the magnetic flux passes through the center leg of the core to the outer legs. Since some of the primary flux links this coil, fundamental voltage is present. The resultant voltage has a high odd-harmonic content due to the leakage flux from the output winding. This leakage flux can return to the output winding by two paths. One bypasses the neutralizing coil. The other path links the neutralizing coil completely. By controlling the reluctances of these magnetic paths, one can control the degree of secondary flux coupled to the neutralizing coil. The neutralizing coil is connected with its polarity additive to the secondary (or output coil) as shown in Figure 3. The output of the newly formed regulator has constant voltage with a waveshape almost completely free of harmonics.
The harmonics are still present in the output winding and also in the neutralizing coil. Since those harmonics present in the neutralizing coil are induced by the flux from the secondary winding, the harmonics in each coil are approximately 180o out of phase. This results in their cancellation. Proper control of turns ratio and magnetic path reluctance contribute to the generation of a sinusoidal output - even with a square wave input! Q. Are there different constant voltage power conditioner designs? A. Yes, there are two basic design concepts. A tap switching design utilizes an electronic circuit along with a traditional transformer core and coil assembly to control the output voltage. As a result, the output voltage tends to be a stepped waveform rather than a smooth sinewave. A ferroresonant design utilizes the electromagnetic induction principle exclusively to produce the desired output voltage. Consequently, the output voltage waveform is a smooth sinewave. The ferroresonant design attenuates transient electrical noise, provides surge suppression per ANSI/IEEE Standards and provides a harmonic free output. These important benefits are not always available with other designs. Q. Should I use a constant voltage power conditioner instead of a UPS? A. Your question involves two different technologies used for differing reasons. 95% of all power quality problems are caused by transient noise, voltage surges, harmonics or frequently changing voltage conditions. Ferroresonant power conditioners provide the solutions for most all of these power quality problems. The primary function of any uninterruptible power supply (UPS) is to provide an alternative voltage source (batteries) to a critical load for some period of time should a complete a power failure occur. Complete power failures account for less than 5% of all power quality problems. For the other 95% of all power quality problems, unless the UPS is the on-line version, the UPS is of no help. Q. How about response time? Will constant voltage power conditioners work as well as other AC regulator types? A. An important advantage of Sola's ferroresonant CVPC is its exceedingly fast response time, compared with other types of AC regulators. Transient changes in supply voltage are usually corrected within 1-1/2 cycles or less; the output voltage will not fluctuate more than a few percent, even during this interval. Q. Can single phase transformers be banked together for three phase operation? A. Yes, this is a common application. Standard configurations include delta-wye and delta-delta connections. Advantages to banking single phase units are:
While banking two or three single phase transformers in a three phase bank is often expedient, it is more expensive than using one three phase transformer. Q. What are voltage adjustment taps? A. In many instances, the supply voltage delivered to the input (primary) of the transformer does not exactly match the voltage rating described. If this happens, the output (secondary) voltage will vary from its nameplate rating because the transformer turns ratio (voltage ratio) is fixed by design. During design and manufacture of the transformer, additional terminations are added to the primary winding to slightly alter the turns ratio. By closely matching the voltage being applied to the appropriate tap, a desirable output voltage can be obtained. Taps are typically located on the primary winding to correct for either sustained high or low voltage conditions on the source. Taps are expressed as a percentage of the nameplate voltage and are designated as FCAN (full capacity above normal) or FCBN (full capacity below normal). Q. How and why is grounding of transformers important? A. Grounding removes static charges that accumulate within a transformer. Grounding also reduces the chance of static discharge causing personal harm and possible equipment damage should the transformer windings accidentally come in contact with the core or enclosure. The actual method of grounding a transformer is simple, defined in NEMA Publication No. ST20, Part 1, Page 4:
Before grounding, make sure all contact surfaces are clean and free of any non-conductive protective coating. Any surface where connections are made must be free of rust, scale and any impediments. Make sure the flexible grounding jumper between the core and coil assembly and case is intact and tight. The metal enclosure, or frame, of any transformer connected to a circuit operating at more than 30 Volts to ground must be effectively grounded. A grounding conductor for the transformer will have a current carrying capacity in accordance with either the National Electric Code or the National Electrical Safety Code. Make sure grounding or bonding meets NEC and local codes. For further information on grounding, refer to ANSI C1 and C2, NEC 1993 Article 250 and NEMA ST20. These publications go into greater detail concerning grounding than space permits here. Q. How does transformer temperature relate to losses, BTU's and enclosures? A. Transformers generate heat! They all do. There is no way of getting around it. Heat is a by-product of the transformation process and heat is due to losses in both the core and coils of the transformer. For most applications, the heat generated is of little concern. But it becomes a concern when determining how much cooling must be provided to compensate for the heat or when the temperature of the enclosure could become a problem. Transformer losses are dependent on loading. A transformer operating at its nameplate KVA generates maximum losses. This is considered to be 100% losses at 100% load, full load losses. A transformer loaded at less than 100% doesn't generate as many losses, but it is not in direct proportion to the amount of the load as indicated in the table below. Transformer losses are expressed in watts.
The top panel of a transformer enclosure may reach a maximum surface temperature of 65°C (per NEMA ST20) above the ambient temperature. In order to determine the total temperature of the enclosure, add the ambient room temperature to the °C rise. Ambient temperatures may be expressed in °F (Fahrenheit), so make sure to use the correct temperature conversion scale: °C
= .555(°F - 32) Transformer losses are measured in watts. Watts must be converted to British Thermal Units (BTU's) in order to determine the amount of heat generated: BTU's = 3.41 x watts/hour
* Approximate threshold of comfort for continuous touching. Q. How can transformer sound be controlled? A. All energized transformers "hum". This "hum" is due to the alternating flux in the core producing a phenomenon known as magnetostriction. Transformer "hum" , commonly referred to as "noise", is primarily produced by the core at a fundamental frequency of twice the applied frequency. Noise is an inherent characteristic of the core and cannot be completely eliminated. Hevi-Duty utilizes the highest quality core steel in its complete line of dry type transformers, to minimize audible sound levels. When selecting a transformer, make certain that the sound levels presented by the manufacturer have been measured in accordance with the American National Standards Institute, and certified by the manufacturer. NEMA Publication No. ST20 and ANSI Standard C89.2 establishes maximum sound levels for dry type transformers. These levels are:
Hevi-Duty has low transformer sound levels due to advanced designs and the manner in which the core and coils are internally isolated from the enclosure. This is done by allowing the entire unit to "float" on vibration dampening pads. One of the major reasons for transformer noise complaints is improper installation. Improper installation and location can increase transformer sound levels 10 decibels or more. Considering that a 3 decibel increase in sound level has the effect of approximately doubling the sound volume as detected by the human ear, a 10 decibel increase in sound level cannot (in most cases) be tolerated. The first step in low sound level transformer installation is specifying the proper location. With the increased popularity in cost saving advantages of high voltage distribution in modern buildings today, it is necessary to locate small dry type transformers relatively close to (or within) occupied areas. Transformers should be located in areas where the noise would be the least objectionable. The maximum sound limit of the transformer to be installed should be compared to the ambient sound level of the installation location. If the transformer is expected to be louder than the ambient of the site, it should be located elsewhere. Don't place a transformer near multiple reflective surfaces. An example of a poor transformer location would be in a corner near the ceiling or the floor. Either of these locations present three reflecting surfaces, and these surfaces will act as a megaphone for the transformer sound. Halls are undesirable too, because of the short distance between opposing reflecting surfaces. When the best possible location has been found, the next step is mounting. Transformers should be mounted on a floor, wall or structure with as great a mass as possible. One guideline is that the mounting surface should weigh at least ten times as much as the transformer. Take care not to mount a transformer on a thin wall (i.e. plywood or a curtain wall) as they amplify the noise much like a drumhead. The prime noise source in the transformer is in the core and coil. The noise from this source is amplified and reflected by any structure solidly connected to it. This includes incoming conduit and conductors. (Flexible devices may be used for this purpose). Good transformer installations try to isolate the transformer from all other components and structures. Q. Is one insulation system better than another? A. During recent years, the terminology used by electrical equipment manufacturers regarding insulation systems has undergone a major change. Letter designations, such as Class A, B, F and H are now Class 105, 150, 180 (sometimes referred to as 185) and 220 respectively. The preceding designations pertain only to the rating of the insulation system. The transformer's rating has also been changed - from Class A, B, F and H, to 55oC rise, 80° C rise, 115oC rise and 150oC rise. What previously was a Class H transformer is now a 150oC rise transformer utilizing a Class 220 insulation system. The insulation rating is the maximum allowable operating temperature for normal transformer life expectancy. The insulation rating is the sum of the transformer rating, ambient operating temperature and hot spot allowance. These maximum temperature limits are set by NEMA standards. Exceeding any one of these will shorten transformer life expectancy.
A well designed transformer, operating within the temperature limits of its insulation system, will have a life expectancy of 20 to 25 years. The design life of transformers having different insulation systems is the same, (lower temperature systems will have the same life as higher temperature systems). The class of insulation used in a particular transformer is a design consideration and such factors as voltage regulation, material cost and availability are factors that the designer must consider. Q. What is balanced loading and why is it important? A. Balancing transformer loads means being sure the transformer winding directly feeding a load is not overloaded beyond its capacity. Most single phase transformer applications involve secondary windings rated for 120/240 Volts. These are frequently connected for three wire service. Since the transformer has two 120 volt secondary windings, each one is capable of supplying only one-half of the transformer's rated KVA capacity. If care is not taken, it is possible to apply a combination of 120 and 240 volt loads that will, while not exceeding the total nameplate rating, exceed the rating of one of the 120 Volt windings. The same is true of three phase transformers, especially those with 208Y/120 Volt or 480Y/277 Volt secondaries. Remember, each of the three secondary windings of a three phase transformer has a maximum capacity of one-third the nameplate KVA rating. It is always necessary to distribute the single and three phase loads as evenly as possible across the three secondary windings without exceeding their capacity. Q. What is impedance? A. Impedance is defined as the vector sum of resistance and reactance which limits the current flow in an AC circuit. When dealing with a transformer, impedance indicates the current limiting effect should you have a short circuit on the secondary. Expressed as a percentage and usually designated as %IZ, impedance along with X/R ratio is used for coordination of fuses and/or circuit breakers. It is also used for calculating the proper interrupting rating of overcurrent protection devices.Calculate the interrupting capacity of a circuit breaker used to protect the primary of a transformer using the following steps: Example
Now determine maximum short circuit current:
The minimum interrupting capacity the circuit breaker must have will be 1042 amps. Typically impedance of distribution transformers runs between 2% and 7%. These percentages vary depending on manufacturer, transformer size, voltage, conductor material and many other factors. Q. What are the different NEMA enclosure types and application definitions? A.
Q. What are the UL enclosure types? A. Underwriters Laboratories adopted a system for rating transformer enclosures which differs somewhat from the NEMA system. The UL system lists just three enclosure types. A UL Type 1 enclosure is intended for indoor service and offers a degree of protection from contact with the device inside the enclosure. UL Type 2 enclosures are also intended for indoor service and provide protection of the equipment inside the enclosure from limited amounts of falling dirt and water. UL Type 3R enclosures can be used either indoors or outdoors and provide protection against rain, sleet, snow and ice formation. The proper UL enclosure rating is listed on the transformer nameplate. Q. Can 60 Hz transformers be used on 50 Hz? A. Yes. 60 Hz transformers can be used on 50 Hz if special precautions are taken. The change in frequency will impact the flux density of the transformer causing it to run hot, as if it were overloaded. To offset this effect, you must decrease the input voltage by approximately 17% (1/6th). This means that a transformer rated for a 480 Volt, 60 Hz input could run at 50 Hz but with a maximum input voltage of 398 volts. On the other hand, 50 Hz transformers can be run on 60 Hz with no ill effects. Q. Is there a quick rule of thumb for determining what transformer K-factor rating is needed for an application? A. Although it is not very scientific and may result in a K-factor rating larger than actually needed, there is a quick and easy method to ballpark K-factor. Take a look at all of the loads that will be powered by the transformer. As you examine the loads ask yourself the following questions:
Once this has been done, add up all of the "electrical" loads that will be on the circuit. Do the same thing for "electronic" loads. When comparing the percentage of "electrical" loads vs. "electronic" loads, if the transformer loading is:
Although "electronic" load will vary in their K-factor rating, by considering all "electronic" loads to be the same, you are assured the sizing is correct and most probably will allow for additional "electronic" loads to be added later. Q. What transformers should be used for low voltage lighting applications and are there any special considerations? A. Buck-boost transformers are ideally suited for handing 12 or 24 Volt low voltage lighting. Although normally field connected as an autotransformer and used for voltage correction, buck-boost transformers can also be used as an isolation transformer to go from 120 or 240 Volts down to 12 and/or 24 Volts. A few tips when using transformers for low voltage lighting applications:
Q. How do I determine the correct overcurrent protection for a 600 Volt class transformer? A. A transformer has all the same component parts as a motor, and like a motor, exhibits an inrush when energized. This inrush current is dependent upon where in the sine wave the transformer was last turned off in relation to the point of the sine wave you are when you energize the transformer. Although transformer inrush could run up to 35 times full load current under no load, it typically is the same as a motor...about 6 to 8 times normal running current. For this reason it is important to use a dual element slow blow type fuse - the same type of fuse you would use with a motor. If using a circuit breaker, select a breaker with a time delay - again the same type you would use with a motor. If the time delay is not sufficient, you may experience "nuisance tripping" - a condition where the breaker trips when energizing the transformer but when you try it again, it works fine. Secondary
overcurrent protection
Q. Are copper windings better than aluminum windings? A. As with most questions of this type pertaining to transformers, a lot depends upon the application and the individual preferences of the person specifying the transformer. Quite often the reason cited for specifying copper windings is copper's high electrical conductivity. During World War II, copper became scarce and was used primarily for the war effort. Several industries turned to aluminum as alternative to copper because it was in good supply, was very stable price-wise and was less expensive than copper. In the 1940's, high-power transmission power lines were converted from copper to aluminum and secondary power distribution networks began utilizing aluminum in the 1950's. Today, virtually all standard transformer lines from the major manufacturers are wound with aluminum. Although copper wound transformers tend to be smaller than comparable aluminum wound transformers offer some distinct advantages over copper wound units:
Aluminum wire has received a negative connotation over the year primarily because of the care that must be taken in making connections. Copper proponents are quick to refer to hotel and mobile home fires that occurred where aluminum wire was present. Upon close examination it was found that the root causes of these problems is related to incorrect wiring devices being used. Copper and aluminum expand at different rates when heated. If aluminum wire is used with wiring devices solely rated for use with copper wire, the connection could loosen as the connection heats up causing the resistance of the connection to increase and the temperature to continue to escalate. Most transformer manufacturers address this problem by making a transition between the aluminum windings, either to a copper lead wire (or bus bar) or by terminating to an AI/Cu lug (or connector). Q. So why are copper wound transformers still specified? A. Copper wound units may be specified because of space limitations. Copper wound units can also be specified due to the environment in which the transformer will be exposed. If the environment would be corrosive to aluminum, copper wound transformers would make sense. Of course, some people may just like copper wound transformers for their own reasons. Sola/Hevi-Duty manufactures aluminum wound transformers but can manufacture copper wound transformers upon special order. Contact your Sola/Hevi-Duty representative for pricing and manufacturing lead times. Q. What is the capacity of the center tap on a 240 delta connection with one phase tapped? A. This is one of the most common transformer application questions. If the transformer is a Sola/Hevi-Duty T5H series the tap is full capacity, but we must define what full capacity means on one phase of a three phase transformer. A three phase transformer built by Hevi-Duty in a ventilated enclosure (standard construction on 15 KVA and above) has a per phase capacity equal to 1/3 of the nameplate rating. Therefore, the tapped phase of a T5H30S has a total capacity of 10 KVA (1/3 of 30 KVA). The 120 volt tap is at the center of this 240 volt winding so the capacity is 5 KVA on either side of the tap (X1 to X6 and X3 to X6).
Q. Ventilated transformers are 150°C rise, and Hard-shell® units are 115°C rise. Why are the Hardshell® units so much warmer to the touch? A. Ventilated transformers are free standing devices placed in a metal housing to protect the unit from the atmosphere, and people from electrical hazards. Ventilated units are surrounded by air, which acts as a cooling medium. The natural convection created by the heat of the transformer causes heat to ventilate through the top of the unit while cool air is drawn in from the bottom (chimney effect). Hardshell® are placed in an enclosure that is filled with electrical grade sand and epoxy. All the air is displaced within this solid epoxy block, so any heat is radiated directly to the enclosure surface. This makes the entire enclosure of the transformer act like a heat sink. All Sola/Hevi-Duty enclosed transformers are UL and CSA listed, your guarantee that the surface temperatures will not rise more than 50°C above ambient. Q. What do the terms "peak inrush current" and "exciting current" mean and how do they relate to transformers? A. Exciting current is the amount of amperage a transformer draws under a no load condition. Another way to look at it is that exciting current is the transformer's "idling" current. Exciting current could also be referred to as no load current although this is not technically accurate. Exciting current is actually made up of two components: no load losses (normally expressed in watts) and reactive power (normally expresses in KVAR). Exciting current varies as a percent of the transformer's nameplate rating depending upon the transformer size. It is not unusual to have an exciting current of approximately 10% on very small transformers (under 1 KVA). On larger transformers, exciting current could be as low as a half of one percent. Peak inrush current is the amount of amperage a transformer draws instantaneously when it is turned on. A transformer has an iron core and works under the principle of magnetic induction. Alternating current flows through a coil of wire (primary winding) and generates a magnetic field. The iron core of the transformer contains most of the magnetism and conducts this magnetism to where it passes through a second coil of wire (secondary winding). Since alternating current travels in the form of a sine wave, the amount of magnetism will fluctuate depending upon the point in the sine wave. As this magnetism cuts through the path of the second coil of wire, it induces a voltage into it. When the transformer is turned off, the iron core retains an amount of residual magnetism depending on where in the sine wave the unit was when turned off. When the transformer is turned on, the greater the difference in the sine wave from the "turn off" point to the "turn on" point determines the amount of inrush current. Inrush current could be very small if everything was in phase, or it could be as high as 20 to 30 times full load current. Although this inrush condition disappears rapidly (in 6 to 10 electrical cycles - one tenth to one sixth of a second) it is the first half electrical cycle that sees the peak amount of inrush. This condition can cause problems with overcurrent devices. If the fuse or breaker is of a "quick trip" variety or not properly sized according to the National Electric Code, the inrush may cause it to trip falsely. Q. What is regulation? A. Under no load, a transformer is not providing voltage to the output. When a load is applied, the voltage will drop slightly. The difference in the output voltage under load vs. unloaded is referred to as the transformer's output regulation and is normally expressed as a percentage. If under no load a transformer had an output voltage of 240 Volts but under load the output voltage was 230 Volts, the difference would be 10 Volts and the regulation would be 10/240 or 4.17%. The power factor of the load can impact the transformer's regulation. General purpose transformers can be used with a variety of loads, the most common being inductive motor loads and resistive loads. For that reason, it is common to express transformer regulation at 100% power factor and also at 80% power factor. Q. Can general purpose transformers be used to power industrial control devices? A. The answer to this question is strictly application related. Industrial control transformers (sometimes referred to as machine tool transformers or control transformers) are specifically design to meet the demands required to power Industrial control devices such as contactors, solenoids and relays. Industrial control devices typically have two power requirements - inrush capacity (the power required to energize or seal the contacts) and sealed capacity (the power required to keep the contacts sealed). It is not uncommon for inrush requirements to be 5, 10 or 15 times the sealed requirements. It is critical that during this period of time requiring the inrush VA requirement that the voltage powering the device remain as steady as possible. Industrial control transformers are designed to provide excellent voltage regulation under inrush conditions. Transformer design engineers accomplish this via a number of different methods. Common methods include compensating transformer secondary windings (to offset secondary winding losses), using a larger conductor on the secondary windings (to cut winding losses) and designing a slightly larger (and usually more expensive) transformer. General purpose transformers provide good voltage regulation up to full nameplate load but the output voltage may drop slightly when the transformer is subjected to a momentary overload. This voltage drop may be beyond what the industrial control device can tolerate. Care needs to be taken if industrial control devices are to be powered from a general purpose transformer. It is not recommended to use a general purpose unit if you are powering one or two devices from the transformer or if you have multiple devices that all "turn on" at the same time. A general purpose transformer may be preferable if you have multiple devices to power that do not "turn on" at the same time and space within the motor control panel is at a premium. Normally a general purpose transformer can be located on the outside of the motor control panel. Q. Are there any special considerations when powering electric motors? A. Different product react differently to motor loads and some are better suited for motor loads than others. For example:
Q. What effect does ambient temperature have on transformer operation? A. Other conditions that need be considered when sizing a transformer to a motor load are ambient temperature (derate the transformer nameplate rating by 8% for ever 10°C above 40°C), altitude (derate nameplate rating by 3% for every 300 feet above 3300 feet), and motor loads that frequently start and stop. If a motor starts several times an hour (such as an air conditioner), the calculated transformer size required should be increased by 20% to offset the effects of inrush heating. If the motor starts very frequently (such as an elevator), the service factor of the load must be used to calculate the proper transformer size. If the service factor of the load is 1.25, the calculated transformer size should be increased by 25%. Remember: Each 10oC over the rated temperature rise cuts the life of your transformer by one half. Q. Can a Delta Primary (three wire) transformer be used on a Wye (four wire) source? A. Yes, any delta primary transformer can be connected to a wye source simply by not using the neutral of the source. This connection will not cause any adverse effects in the operation of the transformer or the source. Q. Can transformers be operated at voltages other than nameplate voltages? A. In some cases transformers may be operated at voltages less than nameplate voltage. In no case should a transformer be operated at a voltage above nameplate voltage unless taps are provided for this purpose. When operating below nameplate voltage the KVA rating of the transformer is reduced due to the increase in current. For example a 10 KVA 480-240 transformer can have a secondary load of 41.6 amps, if the same transformer was operated at 240-120 the same current draw of 41.6 amps equates to a 5 KVA transformer. Q. Can transformers be reverse connected? A. All dry type transformers can be reverse connected without a derating of KVA size, with certain limitations. All Sola/Hevi-Duty three-phase transformers, and all single-phase transformers rated at 1 KVA and above can be reverse connected without any loss in KVA rating. This is allowed due to the turns ratio and the voltage ratio being equal. Sola/Hevi-Duty does not recommend reverse connecting single phase transformers less than 1 KVA since the turns ratio compensation on the low voltage winding will provide voltages lower than name plate voltage. This voltage will be lower for lower KVA sizes Q. Can a single-phase transformer be connected to a three-phase source? A. Yes, the transformer output will be single phase. By connecting two wires from the source (three or four wire) to the transformers primary leads. Care must be used to ensure transformer loading does not create a phase imbalance on the source. Q. What is your Warranty? A. Sola/Hevi-Duty warrants its standard catalog products to be free from defects in materials and workmanship and agrees to correct by repair or replacement, at the option of Sola/Hevi-Duty, products that may fail in service provided that the product has been installed, operated and maintained in accordance with accepted industry practice. Warranty begins upon date of manufacture and is according to the following schedule: 1. Standard catalog transformer and single phase, power 2. Series TPC (Three Phase Power Conditioners) – 2 years. 3. Uninterruptible Power Systems – 2 years unless otherwise stated. 4. DC Power Supplies – 1 year unless otherwise stated. 5. Products manufactured to a purchaser’s specifications – 1 year.
Sola/Hevi-Duty shall not be liable for consequential, contingent, incidental or other damages. Q. What is your UPC Manufacturer's Identification Number? A. 78-3472 Q. Where can I get a copy of the MultiLink software for the 2000, 3000, 4000 and 5K UPS? A. You can download it off of our website. Click here. Q. I am getting 'Communications Loss - Not Protected'? A. This occurs when MultiLink software is not able to communicate with the monitored device.
Q. How do I add licenses so I can shut down more than one computer? A. Go to the drop down menu Configure and select Upgrade License.
Q. How do I add the IP ad | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
