{"id":3144,"date":"2026-01-10T21:48:49","date_gmt":"2026-01-10T13:48:49","guid":{"rendered":"https:\/\/baldor-air.com\/?p=3144"},"modified":"2026-01-10T21:48:54","modified_gmt":"2026-01-10T13:48:54","slug":"10-precautions-to-follow-before-retrofitting-a-screw-air-compressor-with-a-vfd","status":"publish","type":"post","link":"https:\/\/baldor-air.com\/ja\/10-precautions-to-follow-before-retrofitting-a-screw-air-compressor-with-a-vfd\/","title":{"rendered":"10 Precautions to Follow Before Retrofitting a Screw Air Compressor with a VFD"},"content":{"rendered":"

Retrofitting screw air compressors with a Variable Frequency Drive (VFD)<\/a><\/strong> has become a mainstream solution to reduce energy consumption, especially in facilities where compressors account for a significant portion of total electricity usage.<\/p>\n\n\n\n

Since screw compressors are high-power, long-running<\/strong> systems, upgrading to a frequency-controlled solution offers great potential for energy savings and optimized performance<\/strong>. However, before proceeding with a VFD retrofit, several technical aspects must be carefully considered to ensure safe, efficient, and reliable operation<\/strong>.<\/p>\n\n\n\n

In this article, we outline 10 key precautions<\/strong> you should take before converting your screw air compressor to variable frequency control.<\/p>\n\n\n\n

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\u2699\ufe0f 1. Minimize Modifications to Existing Electrical Circuits<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

Preserve the integrity of both the main power circuit<\/strong> and the control circuit<\/strong>. Avoid extensive rewiring. This allows the compressor to switch back to its original operating mode<\/strong> in case of VFD failure or maintenance, without the need to reprogram the PLC.<\/p>\n\n\n\n

\ud83d\udd17 Explore: Screw Compressor Control Systems<\/a><\/em><\/p>\n\n\n\n

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\u26a1 2. Control VFD Start Signal via Star-Delta Contactor<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

\u3092\u78ba\u8a8d\u3059\u308b\u3002 start signal for the VFD<\/strong> is controlled by the delta contactor (KM1) in a star-delta starter. This prevents the VFD from activating while still in the star connection phase.<\/p>\n\n\n\n

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\u23f1\ufe0f 3. Delay Relay Must Exceed VFD Start Time<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

Set the time-delay relay (JS)<\/strong> to a value greater than or equal to the VFD start time<\/strong>. This ensures that the compressor starts without load and avoids abrupt torque spikes.<\/p>\n\n\n\n

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\u23ec 4. Enable VFD\u2019s Low-Frequency Stop Function<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

Utilize the VFD\u2019s delayed stop at lower frequency<\/strong> to ensure smooth shutdown and to reduce mechanical stress on the system.<\/p>\n\n\n\n

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\ud83c\udf9a\ufe0f 5. Set a Safe Minimum Frequency (\u226535 Hz)<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

A frequency setpoint below 35 Hz may cause oil separation failure<\/strong>, leading to oil leakage<\/strong> due to insufficient centrifugal force in the oil-air separator. Adjust the lower frequency limit<\/strong> based on your compressor\u2019s specific wear level and design characteristics.<\/p>\n\n\n\n

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<\/div>\n<\/div>\n\n\n\n
\"variable
variable frequency drive (vfd)<\/figcaption><\/figure>\n\n\n\n
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\ud83d\udca1 6. Choose a VFD with a Higher Power Rating<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

Select a VFD that is one size larger<\/strong> than the compressor motor\u2019s rated power to avoid frequent tripping during startup<\/strong> and to handle startup current peaks.<\/p>\n\n\n\n

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\ud83e\uddf2 7. Add an Output AC Reactor to Filter Harmonics<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

Install an AC output reactor<\/strong> to filter out high-frequency harmonics from the VFD output. This reduces electromagnetic interference (EMI)<\/strong> \u305d\u3057\u3066 noise<\/strong>, and extends the life of the motor insulation.<\/p>\n\n\n\n

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\ud83d\udccd 8. Proper Installation of Pressure Sensors<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

Install pressure sensors close to the compressor<\/strong>\u305d\u3057\u3066 before any filters or valves<\/strong>. Do not place any shut-off valves between the compressor and the sensor. Retain the original mechanical pressure cut-off switch<\/strong> as a backup to ensure safety and prevent overpressure accidents.<\/p>\n\n\n\n

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\ud83d\udd27 9. Adjust System Pressure Control Logic<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

After the VFD retrofit, lower the system\u2019s supply pressure if possible, and switch from a high-pressure, variable-flow<\/strong> setup to a constant-pressure, variable-flow<\/strong> strategy. This enhances energy efficiency while maintaining a stable supply.<\/p>\n\n\n\n

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\ud83d\udd01 10. Retain Dual Control Modes: VFD and Direct Line<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

Design the control system with both VFD and direct line (power frequency)<\/strong> operation options. If the VFD fails or triggers a protective stop, the system should be able to automatically switch to bypass mode<\/strong> to maintain production uptime.<\/p>\n\n\n\n

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\u2705 \u6700\u7d42\u7684\u306a\u611f\u60f3<\/strong><\/h3>\n<\/div>\n<\/div>\n\n\n\n

A well-executed VFD retrofit on a \u30b9\u30af\u30ea\u30e5\u30fc\u30a8\u30a2\u30b3\u30f3\u30d7\u30ec\u30c3\u30b5\u30fc<\/a> can result in significant energy savings, quieter operation, and extended equipment life<\/strong>. However, skipping these critical precautions may cause startup problems, sensor inaccuracies, or even safety hazards.<\/p>\n\n\n\n

For a successful upgrade, always work with professional technicians and refer to manufacturer specifications. Baldor provides advanced solutions including intelligent VFD control, permanent magnet compressors<\/strong>, and system-level energy audits.<\/p>","protected":false},"excerpt":{"rendered":"

Retrofitting screw air compressors with a Variable Frequency Drive (VFD) has become a mainstream solution to reduce energy consumption, especially in facilities where compressors account for a significant portion of total electricity usage. Since screw compressors are high-power, long-running systems, upgrading to a frequency-controlled solution offers great potential for energy savings and optimized performance. However, before proceeding with a VFD retrofit, several technical aspects must be carefully considered to ensure safe, efficient, and reliable operation. In this article, we outline 10 key precautions you should take before converting your screw air compressor to variable frequency control. \u2699\ufe0f 1. Minimize Modifications to Existing Electrical Circuits Preserve the integrity of both the […]<\/p>","protected":false},"author":1,"featured_media":3145,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","footnotes":""},"categories":[32],"tags":[266,265,101,239],"class_list":{"0":"post-3144","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-blog","8":"tag-baldor-air-compressor-vfd-conversion","9":"tag-energy-saving-compressor-solutions","10":"tag-screw-air-compressors","11":"tag-variable-frequency-drive-vfd"},"_links":{"self":[{"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/posts\/3144","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/comments?post=3144"}],"version-history":[{"count":1,"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/posts\/3144\/revisions"}],"predecessor-version":[{"id":3146,"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/posts\/3144\/revisions\/3146"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/media\/3145"}],"wp:attachment":[{"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/media?parent=3144"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/categories?post=3144"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/baldor-air.com\/ja\/wp-json\/wp\/v2\/tags?post=3144"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}