1PCS 4000W AC 220V SCR Adjustable Motor Speed Controller Control Dimming Dimmers Voltage Regulator High-power 1PC 4000W Power module 220V SCR Voltage Regulator, Dimmer Motor Speed Controller Thermostat HighIdeal for Dimming and Motor Please take a look before placing an order: This product has an AC voltage of 220V input and output, and can only be reduced in voltage. It can only be adjusted when connected to a load. It is useless to connect it to a multimeter without load, not a transformer. Please read all the instructions on the product page before placing an order! Specification parameters: Product name: 4000W AC voltage regulator Thyristor model: BTA41600B Size: length 85 * width 55 * height 38mm, knob inner hole 6mm Maximum power: 4000W "resistive load limit power", power should be reduced for long-term use. Efficiency: Over 90% Working voltage: AC 220V Voltage regulation: AC 10-220V Note that the load must be connected first before voltage regulation. Controllable silicon is mainly used for resistive loads such as electric heating filament incandescent lamps. Most single-phase AC motors can also be used, but it is not guaranteed that they can be used. For other types of loads, please confirm by the buyer. Fuses are not omnipotent, they have a response time. If the current is too high, besides burning out the fuse, the module may also be burned out. The plastic cover on the connector cannot be fully opened due to the installation of the outer shell. The screwdriver should be slightly turned off, and caution should be taken when opening it. Excessive force can easily break the cover, which may be crushed during shipping. It is a vulnerable part, but it will not affect the use of the module.