Frequency converter power saving and use

1. If two identical motors are working at 50Hz power frequency, one uses the inverter, one does not, and the speed and torque are in the rated state of the motor, can the inverter save power? How much can you save?
A: For this situation, the inverter can only improve the power factor and does not save power.
2. If the torque of these two motors does not reach the rated torque of the motor (frequency, speed is still the same 50HZ), how much electricity can save the inverter?
Answer: If automatic energy-saving operation is used, the inverter can be stepped down at this time, which can save part of the power, but the power saving is not obvious.
3. The same conditions, how much can be saved under no-load conditions, which provinces are more in these three states?
A: The drag-type load no-load state can not save much power.
1. Frequency conversion is not everywhere to save power. There are many occasions where frequency conversion does not necessarily save power.
2. As an electronic circuit, the inverter itself consumes power (about 3-5% of rated power).
3. The inverter runs at the power frequency and has a power saving function, which is a fact. But his preconditions are:
First, high power and is a fan/pump type load;
Second, the device itself has a power saving function (software support);
Third, continuous operation in the long run. This is the three conditions that reflect the power saving effect.
4. What is the starting current and starting torque of the motor when the inverter is running?
The inverter is operated, and the frequency and voltage are increased correspondingly with the acceleration of the motor. The starting current is limited to 150% of the rated current (125% to 200% depending on the model). When starting directly with a commercial power supply, the starting current is 6 to 7 times, so a mechanical and electrical impact will occur. It can be started smoothly with the inverter drive (starting time becomes longer). The starting current is 1.2 to 1.5 times of the rated current, and the starting torque is 70% to 120% of the rated torque. For the inverter with automatic torque boosting function, the starting torque is 100% or more. Full load start.
5. In the same factory, the large motors move together, and the inverter stops during operation. Why?
When the motor starts, the starting current corresponding to the capacity will flow, and the transformer on the stator side of the motor will produce a voltage drop. When the motor capacity is large, the voltage drop will have a large influence. The inverter connected to the same transformer will make an undervoltage or instantaneous stop. The judgment, and thus the protection function, sometimes causes the operation to stop.
6. Is there a limit to the installation direction when installing the inverter?
The structure of the inside and the back of the inverter takes into account the cooling effect. The relationship between the upper and lower sides is also important for ventilation. Therefore, the longitudinal position of the unit type in the disc and hanging on the wall is as vertical as possible.
7. Is it possible to use a soft start without directly applying the motor to a fixed frequency inverter?
It is ok at very low frequencies, but if the given frequency is high, the conditions for direct starting of the commercial power supply are similar. A large starting current (6 to 7 times rated current) will flow, and the motor will not start because the inverter cuts off the overcurrent.
8. What should I pay attention to when the motor runs over 60Hz?
(1) Machines and devices are required to operate at this speed (mechanical strength, noise, vibration, etc.).
(2) The motor enters the constant power output range, and its output torque should be able to maintain its work (the output power of the shaft such as the fan and pump increases proportionally to the cube of the speed, so pay attention when the speed is slightly increased).
(3) The problem of bearing life is to be fully considered.
(4) For motors with medium capacity or above, especially 2-pole motors, it is necessary to discuss with the manufacturer carefully when operating at 60 Hz or higher.
9. Can the inverter drive the gear motor?
Depending on the structure of the reducer and the way it is lubricated, there are a number of issues to be aware of. In the structure of the gear, 70 to 80 Hz is usually considered as the maximum limit. When oil lubrication is used, continuous operation at low speed is related to the damage of the gear.
10. Can the inverter be used to drive a single-phase motor? Can I use a single-phase power supply?
The machine basically can't be used. For the single-phase motor of the governor switch-start type, it will burn out under the speed range below the operating point.
Auxiliary winding; for capacitor starting or capacitor operation, capacitor explosion will be induced. The power supply of the inverter is usually three-phase, but for small-capacity, it also works with single-phase power.
11. What is the power consumed by the inverter itself?
It is related to the model, operating status, frequency of use, etc. of the inverter, but it is difficult to answer. However, the efficiency of the inverter below 60 Hz is about 94% to 96%.
12. Why can't I use it continuously in the whole area of 6~60Hz?
Generally, the motor is cooled by the blades on the outer fan or the rotor end ring mounted on the shaft. If the speed is lowered, the cooling effect is lowered, so that the same heat as the high-speed operation cannot be withstood, and the load torque at a low speed must be reduced, or A large-capacity inverter is combined with a motor or a dedicated motor.
13. What should you watch out for when using a motor with a brake?
The brake excitation circuit power supply should be taken from the input side of the frequency converter. If the brake is activated while the inverter is outputting power, it will cause an overcurrent cut. Therefore, the brake should be actuated after the inverter stops outputting.
14. How long does the inverter last?
Although the inverter is a stationary device, it also has consumption devices such as a filter capacitor and a cooling fan. If they are regularly maintained, it is expected to have a life of more than 10 years.