Starting an asynchronous three-phase motor from a single-phase network
In one of our previous articles, we discussed the question of starting an asynchronous three-phase motor from a single-phase network. In this article, we will focus on one of the methods – starting through frequency converters.
Frequency Converters
Most well-known manufacturers of frequency converters offer a solution that allows supplying single-phase voltage of 220V at the input and receiving three-phase voltage of 220V at the output. It is important that the motor is capable of being connected to a three-phase system of 220V. This can be verified by referring to the motor's nameplate, which should indicate a voltage of 220/380V.
Checking Connection Capability
The nameplate should specify that the motor can be connected in a "delta/star" configuration. For example, in the "delta" configuration, the voltage will be 3-phase 220V, whereas in the "star" configuration – 380V. The current in the "delta" configuration is 2.85A, while in the "star" configuration – 1.65A. Current is an important factor when choosing a frequency converter. It is crucial to note that the power of the motor when connected in "star" or "delta" configurations remains unchanged, which is an advantage compared to connection via capacitors.
If the nameplate has lost its readability, you can open the connection box and check the terminals. If it is known that the motor operated on "star" with a voltage of 380V, then when connected in a star configuration, the three terminals should be shorted. When connected in a delta configuration, the jumpers should be installed in pairs. This is the most common type of motor with a "delta/star" connection configuration of 220V/380V.
Power of Frequency Converters
For cases where there is 1 phase of 220V at the input and 3 phases of 220V at the output, many manufacturers offer solutions with a power of up to 2.2 kW. This is related to the fact that motors with a power exceeding 2.2 kW typically use 3-phase voltage to avoid voltage drops. However, we can offer frequency converters that accept 1 phase of 220V at the input and provide 3 phases of 220V at a power of up to 7.5 kW.
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