There are two methods of connecting a wattmeter in a circuit as shown in fig. (a) and (b). Due to the power loss in pressure coil and current coil, there is error in the measurement of power.<\/p>\n
The wattmeter measures the power consumed by the load plus the power loss in c.c. or p.c.<\/p>\n
![\"Different](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/different-wattmeter-connections.jpg\")
<\/p>\n
Connection-I:<\/strong><\/p>\n Let rc<\/sub> <\/em>= resistance of current coil, Ic<\/sub> <\/em>= current through current coil = load current Note:<\/strong><\/p>\n Connection-II:<\/strong><\/p>\n Let the resistance of the c.c. be very small, IP<\/sub><\/em> = current through the pressure coil<\/p>\n Note:<\/strong><\/p>\n Where I<\/em> is high then, IP<\/sub> will be low and error will be less. I c<\/sub>2<\/sup>rc<\/sub> = V2\/<\/sup><\/em>Rs<\/sub><\/em><\/p>\n Error due to Pressure Coil Inductance<\/strong><\/p>\n Fig. (a) and (b) shows an electrodynamometer wattmeter without pressure coil inductance and with pressure coil inductance.<\/p>\n Without Inductance in p.c.:<\/strong><\/p>\n Here, current I1<\/sub><\/em> will be in phase with applied voltage V<\/p>\n Wattmeter with Pressure Coil Inductance:<\/strong><\/p>\n Two Wattmeter Method<\/strong><\/p>\n For star connection, we have<\/p>\n Measurement of Power Factor<\/strong><\/p>\n \u2234 p.f. of circuit = cos \u03c6<\/p>\n Measurement of Reactive Power using Wattmeter<\/strong><\/p>\n For measurement of reactive power using wattmeter, the current coil is connected between one of the phases of R, Y, B (i.e., R) then, the potential coil should be connected between the remaining two phases (i.e., Y and B). Below figure shows the connection diagram for the measurement of 3 phase reactive power using wattmeter.<\/p>\n Variation in Wattmeter Readings<\/strong><\/p>\n Remember:<\/strong><\/p>\n << Previous<\/a> | Next >><\/a> <\/p>\n","protected":false},"excerpt":{"rendered":" The error occurring in electrodynamometer wattmeters are explained as under : 1. Error due to Connection There are two methods<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[389,5],"tags":[404,406,405,403,401,402],"class_list":["post-1327","post","type-post","status-publish","format-standard","hentry","category-electrical-electronic-measurements","category-ee","tag-inductance","tag-measurement-of-power-factor","tag-phasor-diagram","tag-pressure-coil-inductance","tag-true-power","tag-wattmeter"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/1327","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/comments?post=1327"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/1327\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=1327"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=1327"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=1327"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nHere, p.c. is connected on the supply side.
\nHere, wattmeter measures the power in its current coil in addition to the power consumed by load<\/p>\n![\"True](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/true-power.jpg\")
<\/p>\n\n
![\"Wattmeter\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/wattmeter.jpg\")
<\/p>\n
\n\u2022 Therefore, Connection-II is preferred when the load current is higher.
\n\u2022 When error in Connection-I and II are equal then,<\/p>\n![\"Error](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/error-due-to-pressure-coil-inductance.jpg\")
<\/p>\n![\"Inductance\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/Inductance.jpg\")
<\/p>\n![\"Phasor](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/phasor-diagram.jpg\")
<\/p>\n![\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/pressure-coil-inductance.jpg\")
<\/p>\n![\"\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/Screenshot-2024-07-11-125225.png\")
<\/p>\n![\"\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/Screenshot-2024-07-11-125311.png\")
<\/p>\n![\"Two](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/two-wattmeter-method.jpg\")
<\/p>\n\n
![\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/phasor-diagram-for-wattmeter.jpg\")
<\/p>\n![\"Phasor\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/phasor-1.jpg\")
<\/p>\n![\"Measurement](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/measurement-of-power-factor.jpg\")
<\/p>\n![\"Measurement](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/measurement-of-reactive-power.jpg\")
<\/p>\n![\"Variation](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/variation-in-wattmeter-readings.jpg\")
<\/p>\n\n
\n Must Read: <\/strong> What are the Electrical and Electronics Measurements?<\/strong><\/a><\/p>\n