Here's an article that provides three medical devices as examples of the necessity of using UPS. I hope it will be helpful to you.
1. DR
A typical DR's power supply requirements include voltage fluctuation of ≤ 10%, power supply power of ≥ 50 KW, internal resistance of power supply of ≤ 0.3 Ω, and grounding resistance of ≤ 4.0 Ω. The input circuit of DR's tube generally comprises a rectifier, high-frequency inverter, booster, and high-voltage rectifier to ensure pure high-voltage direct current. Because this circuit uses many power electronic devices and is sensitive to EMI, the front-end power supply equipment (voltage stabilizer or UPS) must pass EMC testing.
The core technology of DR is reflected in the flat panel detector, a precision equipment that plays a decisive role in the imaging quality of DR. Nowadays, many DRs have dedicated temperature detection and control units inside. Under normal circumstances, even when turned off, the detector must always be powered on to ensure a constant temperature and humidity (20-24 ℃; 30% -70% RH). If there is a power outage, the temperature module will stop working. The temperature rise of the detector is a slow process, requiring at least 4 hours of power before reaching a stable calibration state. If the power is cut off at night and turned on the next day for inspection, it is difficult to keep the detector in a stable state at the beginning, which poses a risk of image quality problems.
2. CT Scanner
CT also uses X-ray imaging, but it is much more complex, so its requirements for power and environment are much higher than DR.
The stable and high-quality pure sine wave of UPS has a direct impact on the clear imaging and precise positioning of medical equipment. Some medical devices have significant fluctuations in the dynamic demand for electricity.
For example, a typical CT requires approximately 20 KW of electrical power for continuous operation, but requires an instantaneous power of 90 KW or more, with multiple peaks occurring per minute, each lasting several tens of microseconds or more. At the same time, it is required that during this peak power output period, the voltage fluctuation range should not exceed 6% of the rated voltage. Some cardiovascular imaging devices require higher dynamic characteristics, with a power requirement of about 5 KW for continuous operation but a transient power requirement of up to 170 KW for a duration of 10-40 ms, before returning to 5 KW and repeating 12 times per minute. Many UPS cannot adapt to this load characteristic, which requires the UPS to have good dynamic response characteristics. Click here and find out Gooden UPS solutions for reference.
3. MRI equipment
MRI uses the principle of magnetic resonance to reconstruct human information. Its characteristics are no radiation damage to the human body and rich image information, but more susceptible to artifact interference. The main reasons for producing artifacts include power quality, EMI, poor temperature, and humidity control, all of which can cause interference with RF signals or magnetic fields.
In addition to magnetic shielding for the scanning room, MRI has strict requirements for the surrounding and indoor environment. Generally, there should be no large moving metal objects such as elevators within 7.5 meters from the center point of the magnet and no ferromagnetic substances within 1.1 meters from the center point of the magnet. Therefore, the main machine (RF controller and power amplifier unit), voltage stabilizer or UPS, constant temperature and humidity air conditioning, etc. of MRI are placed in the equipment room.
During MRI scanning, a large instantaneous power is required, which generates a large instantaneous impulse current and a large instantaneous voltage drop. Therefore, the power supply of the MRI system requires an independent feeder directly from the hospital's main substation to the magnetic resonance dedicated distribution cabinet, and a certain power margin should be reserved for wire diameter selection; The line length, internal resistance, distance, and three-phase imbalance must meet the requirements of the equipment manufacturer. It is recommended to use UPS with a built-in isolation transformer, with a capacity of 200 KVA or above.
Additionally, a low-power auxiliary power supply is required specifically for the host temperature controller TCU and equipment air conditioning to ensure normal temperature control of the MRI magnet during power outages. After a power outage, if the nuclear magnetic cooling head cannot be properly reset, it will cause the temperature of the magnet to rise and the liquid helium inside the magnet to evaporate. In severe cases, it can cause overloading and require the entire equipment to be returned to the factory for maintenance, resulting in significant losses.
The computer of the MRI workstation also needs a continuous and stable uninterrupted power supply to ensure that the image data stored in the device will not be lost due to unexpected power outages.
MRI also has different electrical power requirements in different working modes. When scanning different parts of the human body, the required power supply varies depending on the settings.
In addition, MRI generates a large number of harmonics during the scanning process, which puts higher demands on UPS output. Through actual testing, it was found that the total harmonic THDi of a mainstream brand 3.0T MRI is about 30% to 40%.
Therefore, the UPS equipped for these large medical devices must meet the requirements of instantaneous power and continuous power, and the output voltage of the UPS must remain stable in any state. This also requires that the dynamic response characteristics of UPS inverters must be able to meet the dynamic load requirements of large medical equipment. If the capacity of UPS is insufficient or the dynamic response capability is insufficient, the input voltage of medical equipment will exceed the rated voltage range when the power reaches its peak, leading to artifacts, lock-in, and even system failures.
In addition, there are several points to note:
1. If the EMC design and manufacturing process of UPS are poor, the inverter inside the UPS may become a source of interference.
2. Some large medical devices contain high-power electric motors, which may require a large starting current when starting, and the motors are inductive loads. These devices typically require a UPS with much higher nominal power than medical devices.
In summary, large medical equipment in hospitals has high requirements for electrical energy quality and power supply continuity. Using a stable and reliable UPS is an effective solution. However, the performance and parameters of various types of equipment are different. Therefore, when configuring UPS, it is necessary to confirm a detailed selection plan with the UPS manufacturer.
When manufacturers configure front-end UPS, they need to understand the electrical and mechanical parameters of medical equipment. Including:
1. Continuous power demand
2. Transient power demand (including peak power, duration of each time, frequency of demand)
3. Voltage adjustment requirements (fluctuation range, etc.)
4. Other requirements (land occupation, load-bearing capacity, etc.)
In recent years, more and more hospitals have realized the value of equipping MRI machines with high-power UPS, but there are still many designs that follow the old habit of only equipping the control unit of MRI with small UPS and using a voltage stabilizer for the host.
The advantages and disadvantages of these two schemes are compared as follows:
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