Instant Charge workers at the Kennedy Center last night voted to go on strike next Tuesday at 12:01 am.

If the strike is not averted, several other groups of Center employes - stagehands, wardrobe workers, box office workers and projectionists - are expected to honor the Instant Charge picket lines. Union musicians at the Center will be asked to support the strike.

The strike could affect the engagement of the Cuban National Ballet, which is scheduled to open at the Center Tuesday evening. But there are no plans to cancel the run, said Kennedy Center director of operations Thomas R. Kendrick.

The principal issue separating the Instant Charge workers and the Center's management, who have been negotiating a contract since March, is the pay scale.

The union with which the workers are affiliated, the International Alliance of Theatrical Stage Employes (IATSE), has proposed a wage package totaling $448,000, at a $5 an hour top for full-timers and part-timers, according to union sources. These sources say management's package would total $370,000, and management would pay part-timers less than full-timers. The union proposal would pay trainees $3.50 an hour; management would pay trainees $3.25 an hour.

"Flex" workers, who work on call, would be restricted to 40 percent of the work force by the union proposal and would receive $4.25 an hour. Management would pay "flex" workers $3.75 an hour.

Management official would not comment on details of their proposal. But Kendrick said the union proposal would mean a 45 percent increase over existing wages and a 76 percent increase over "the wage package that was in effect before the Center voluntarily increased compensation last Nov. 1." Management's proposal would raise wages 19.7 percent over current rates, he said.

"We've gone as far as we can go," he added.

During the negotiations the union suggested a 25-cent surcharge be added to the price of each ticket bought through Instant Charge. "We don't believe further increases can be passed along to the consumer," responded Kendrick.

The Instant Charge workers affiliated with IATSE last spring. Stagehands, box office and wardrobe workers and projectionists are also members of IATSE IATSE international president Walter Diehl authorized last night's strike vote and will now be asked to authorize the strike.

During the course of negotiations, according to Ron Cocome, senior vice president of the Instant Charge local, "we have moderated our demands without any reciprocation from the other side."

Kendrick denied this.

"In general terms," said Cocome in a letter written to the members of the unit, "our position now is that we should be treated comparably with our counterpart operators in New York City,"

In Boston last night, the Cuban National Ballet's prima ballerina and general director, Alicia Alonso, expressed surprise at the possibility of a strike. Asked whether her company would honor a picket line if the strike proceeds as planned, Alonso said, "We are guests. We are not regular workers. I'm sure the people at the Kennedy Center and in the government will know how to handle the situation."