Tesla Inc. said cumulative global sales of its Model 3 sedan have surpassed 3 million units, reinforcing the carmaker’s position in the mass-market electric-vehicle segment. The milestone comes eight years after the model’s 2017 debut and makes the Model 3 the first electric passenger car to reach that volume, according to company figures. Tesla added that the sedan has been the world’s best-selling electric sedan for seven consecutive years, a pace that works out to roughly one sale every 73 seconds. The record underscores sustained demand for the company’s entry-level vehicle even as competition in the battery-powered car market intensifies. The Model 3 is built in Fremont, California, and at Tesla’s Shanghai plant, where an updated version began deliveries last year.