ELECTRIC MOTORS CAES（电动马达压缩空气蓄能）.pdfVIP

ELECTRIC MOTORS Enclosures for Motors Types of motor enclosures generally used in farm applications: (1) Open type; drip proof or splash-proof. A general purpose motor for use in dry locations which are relatively free of splashing liquids and dust particles. (2) Totally enclosed. For applications where the motor will be subject to dust, moisture, wash water, foreign particles, or for outdoor usage. Recommended for most farm uses. (3) Explosion proof. Designed to prevent ignition of any explosive gases or dust and dirt which may surround the motor. Electric Motor Protection To insure long motor life and freedom from electrical hazards, motors must be protected from short circuits and overload. If the motor is overloaded it will draw excessive current and overheating will result. Overheating will cause the insulation on the windings to breakdown and may cause the bearings to seize. As a general rule, a general purpose motor is overheating if you cannot hold your hand on it for a few seconds. A thermal overload switch built into the motor affords the best protection against motor overloading. Built-in thermal protective devices may be of either the automatic-reset type or manual-reset type. A manual-reset type is recommended for general purpose use. An automatic-reset type protective device should not be used on any motor where automatic restarting of the motor could cause a personal injury or cause damage to the machinery being operated. Motors may draw 3 to 12 times their normal running current when starting, thus ordinary single-element fuses are not satisfactory for protecting motors. The fuse in the circuit to which a motor is connected is designed to protect the wiring and not the motor. Thus, unless complete fusing protection (short and overload) is provided in the motor a separate d